DATASHEET

ISL6323
Hybrid SVI/PVI
Data Sheet
May 17, 2011
FN9278.5
Monolithic Dual PWM Hybrid Controller
Powering AMD SVI Split-Plane and PVI
Uniplane Processors
Features
The ISL6323 dual PWM controller delivers high efficiency
and tight regulation from two synchronous buck DC/DC
converters. The ISL6323 supports hybrid power control of
AMD processors which operate from either a 6-bit parallel
VID interface (PVI) or a serial VID interface (SVI). The dual
output ISL6323 features a multiphase controller to support
uniplane VDD core voltage and a single phase controller to
power the Northbridge (VDDNB) in SVI mode. Only the
multiphase controller is active in PVI mode to support
uniplane VDD only processors.
• Configuration Flexibility
- 2-Phase Operation with Internal Drivers
- 3- or 4-Phase Operation with External PWM Drivers
A precision uniplane core voltage regulation system is
provided by a 2- to 4-phase PWM voltage regulator (VR)
controller. The integration of two power MOSFET drivers,
adding flexibility in layout, reduce the number of external
components in the multiphase section. A single phase PWM
controller with integrated driver provides a second precision
voltage regulation system for the North Bridge portion of the
processor. This monolithic, dual controller with integrated
driver solution provides a cost and space saving power
management solution.
For applications which benefit from load line programming to
reduce bulk output capacitors, the ISL6323 features output
voltage droop. The multiphase portion also includes advanced
control loop features for optimal transient response to load
application and removal. One of these features is highly
accurate, fully differential, continuous DCR current sensing for
load line programming and channel current balance. Dual
edge modulation is another unique feature, allowing for
quicker initial response to high di/dt load transients.
Ordering Information
PART
NUMBER
(Note)
PART
MARKING
ISL6323CRZ* ISL6323 CRZ
ISL6323IRZ*
ISL6323 IRZ
TEMP.
(°C)
0 to +70
• Processor Core Voltage Via Integrated MultiPhase
Power Conversion
• Serial VID Interface Inputs
- Two Wire, Clock and Data, Bus
- Conforms to AMD SVI Specifications
• Parallel VID Interface Inputs
- 6-bit VID input
- 0.775V to 1.55V in 25mV Steps
- 0.375V to 0.7625V in 12.5mV Steps
• Precision Core Voltage Regulation
- Differential Remote Voltage Sensing
- ±0.5% System Accuracy Over-Temperature
- Adjustable Reference-Voltage Offset
• Optimal Processor Core Voltage Transient Response
- Adaptive Phase Alignment (APA)
- Active Pulse Positioning Modulation
• Fully Differential, Continuous DCR Current Sensing
- Accurate Load Line Programming
- Precision Channel Current Balancing
• Variable Gate Drive Bias: 5V to 12V
• Overcurrent Protection
• Multi-tiered Overvoltage Protection
• Selectable Switching Frequency up to 1MHz
• Simultaneous Digital Soft-Start of Both Outputs
• Processor NorthBridge Voltage Via Single Phase
Power Conversion
PACKAGE
(Pb-free)
PKG.
DWG. #
48 Ld 7x7 QFN L48.7x7
-40 to +85 48 Ld 7x7 QFN L48.7x7
*Add “-T” suffix for tape and reel. Please refer to TB347 for details on
reel specifications.
NOTE: These Intersil Pb-free plastic packaged products employ
special Pb-free material sets, molding compounds/die attach
materials, and 100% matte tin plate plus anneal (e3 termination
finish, which is RoHS compliant and compatible with both SnPb and
Pb-free soldering operations). Intersil Pb-free products are MSL
classified at Pb-free peak reflow temperatures that meet or exceed
the Pb-free requirements of IPC/JEDEC J STD-020.
• Precision Voltage Regulation
- Differential Remote Voltage Sensing
- ±0.5% System Accuracy Over-Temperature
• Serial VID Interface Inputs
- Two Wire, Clock and Data, Bus
- Conforms to AMD SVI Specifications
• Overcurrent Protection
• Continuous DCR Current Sensing
• Variable Gate Drive Bias: 5V to 12V
• Simultaneous Digital Soft-Start of Both Outputs
• Selectable Switching Frequency up to 1MHz
• Pb-Free (RoHS Compliant)
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Copyright Intersil Americas Inc. 2007, 2008, 2011. All Rights Reserved
Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.
All other trademarks mentioned are the property of their respective owners.
ISL6323
Pinout
COMP_NB
ISEN_NB-
ISEN4+
ISEN4-
ISEN3+
ISEN3-
PVCC_NB
LGATE_NB
BOOT_NB
UGATE_NB
PHASE_NB
VDDPWRGD
ISL6323
(48 LD QFN)
TOP VIEW
48
47
46
45
44
43
42
41
40
39
38
37
FB_NB
1
36
PWM4
ISEN_NB+
2
35
PWM3
RGND_NB
3
34
PWROK
VID0/VFIXEN
4
33
PHASE1
VID1/SEL
5
32
UGATE1
VID2/SVD
6
31
BOOT1
VID3/SVC
7
30
LGATE1
VID4
8
29
PVCC1_2
VID5
9
28
LGATE2
VCC
10
27
BOOT2
FS
11
26
UGATE2
RGND
12
25
PHASE2
2
13
14
15
16
17
18
19
20
21
22
23
24
VSEN
OFS
DVC
RSET
FB
COMP
APA
ISEN1+
ISEN1-
ISEN2+
ISEN2-
EN
49
GND
FN9278.5
May 17, 2011
ISL6323
Functional Pin Description
PIN NUMBER
SYMBOL
DESCRIPTION
1, 48
FB_NB and
COMP_NB
These pins are the internal error amplifier inverting input and output respectively of the
NB VR controller. FB_NB, VDIFF_NB, and COMP_NB are tied together through external
R-C networks to compensate the regulator.
2, 47
ISEN_NB+,
ISEN_NB1-
These pins are used for differentially sensing the North Bridge output current. The
sensed current is used for protection and load line regulation if droop is enabled.
Connect ISEN_NB- to the node between the RC sense element surrounding the inductor.
Tie the ISEN_NB+ pin to the VNB side of the sense capacitor.
3
RGND_NB
This pin is an input to the NB VR controller precision differential remote-sense amplifier
and should be connected to the sense pin of the North Bridge, VDDNBFBL.
4
VID0/VFIXEN
If VID1 is LO prior to enable [SVI Mode], the pin functions as the VFIXEN selection input
from the AMD processor for determining SVI mode versus VFIX mode of operation.
If VID1 is HI prior to enable [PVI Mode], the pin is used as DAC input VID0. This pin has
an internal 30µA pull-down current applied to it at all times.
5
VID1/SEL
This pin selects SVI or PVI mode operation based on the state of the pin prior to enabling
the ISL6323. If the pin is LO prior to enable, the ISL6323 is in SVI mode and the dual
purpose pins [VID0/VFIXEN, VID2/SVC, VID3/SVD] use their SVI mode related
functions. If the pin held HI prior to enable, the ISL6323 is in PVI mode and dual purpose
pins use their VIDx related functions to decode the correct DAC code.
6
VID2/SVD
If VID1 is LO prior to enable [SVI Mode], this pin is the serial VID data bi-directional
signal to and from the master device on AMD processor. If VID1 is HI prior to enable [PVI
Mode], this pin is used to decode the programmed DAC code for the processor. In PVI
mode, this pin has an internal 30µA pull-down current applied to it. There is no pull-down
current in SVI mode.
7
VID3/SVC
If VID1 is LO prior to enable [SVI Mode], this pin is the serial VID clock input from the
AMD processor. If VID1 is HI prior to enable [PVI Mode], the ISL6323 is in PVI mode and
this pin is used to decode the programmed DAC code for the processor. In PVI mode, this
pin has an internal 30µA pull-down current applied to it. There is no pull-down current
in SVI mode.
8, 9
VID4, VID5
These pins are active only when the ISL6323 is in PVI mode. When VID1 is HI prior to
enable, the ISL6323 decodes the programmed DAC voltage required by the AMD
processor. These pins have an internal 30µA pull-down current applied to them at all
times.
10
VCC
VCC is the bias supply for the ICs small-signal circuitry. Connect this pin to a +5V supply
and decouple using a quality 0.1µF ceramic capacitor.
11
FS
A resistor, placed from FS to Ground or from FS to VCC, sets the switching frequency of
both controllers. Refer to Equation 1 for proper resistor calculation.
R T = 10
[ 10.61 – 1.035 log ( f s ) ]
(EQ. 1)
With the resistor tied from FS to Ground, Droop is enabled. With the resistor tied from
FS to VCC, Droop is disabled.
12, 13
RGND, VSEN
14
OFS
The OFS pin provides a means to program a DC current for generating an offset voltage
across the resistor between FB and VSEN The offset current is generated via an external
resistor and precision internal voltage references. The polarity of the offset is selected
by connecting the resistor to GND or VCC. For no offset, the OFS pin should be left
unconnected.
15
DVC
The DVC pin is a buffered version of the reference to the error amplifier. A series resistor
and capacitor between the DVC pin and FB pin smooth the voltage transition during
VID-on-the-fly operations.
3
VSEN and RGND are inputs to the core voltage regulator (VR) controller precision
differential remote-sense amplifier and should be connected to the sense pins of the
remote processor core(s), VDDFB[H,L].
FN9278.5
May 17, 2011
ISL6323
Functional Pin Description (Continued)
PIN NUMBER
SYMBOL
DESCRIPTION
16
RSET
Connect this pin to the VCC pin through a resistor (RSET) to set the effective value of
the internal RISEN current sense resistors. The values of the RSET resistor should be no
less than 20kΩ and no more than 80kΩ. A 0.1µF capacitor should be placed in parallel to
the RSET resistor.
17, 18
FB, COMP
These pins are the internal error amplifier inverting input and output respectively of the
core VR controller. FB, VSEN and COMP are tied together through external R-C networks
to compensate the regulator.
19
APA
Adaptive Phase Alignment (APA) pin for setting trip level and adjusting time constant. A
100µA current flows into the APA pin and by tying a resistor from this pin to COMP the
trip level for the Adaptive Phase Alignment circuitry can be set.
20, 21, 22, 23,
43, 44, 45, 46
ISEN1+, ISEN1-,
ISEN2+, ISEN2-,
ISEN3-, ISEN3+,
ISEN4-, ISEN4+
These pins are used for differentially sensing the corresponding channel output currents.
The sensed currents are used for channel balancing, protection, and core load line
regulation.
Connect ISEN1-, ISEN2-, ISEN3-, and ISEN4- to the node between the RC sense
elements surrounding the inductor of their respective channel. Tie the ISEN+ pins to the
VCORE side of their corresponding channel’s sense capacitor.
24
EN
This pin is a threshold-sensitive (approximately 0.85V) system enable input for the
controller. Held low, this pin disables both CORE and NB controller operation. Pulled high,
the pin enables both controllers for operation.
When the EN pin is pulled high, the ISL6323 will be placed in either SVI or PVI mode.
The mode is determined by the latched value of VID1 on the rising edge of the EN signal.
A third function of this pin is to provide driver bias monitor for external drivers. A resistor
divider with the center tap connected to this pin from the drive bias supply prevents
enabling the controller before insufficient bias is provided to external driver. The resistors
should be selected such that when the POR-trip point of the external driver is reached,
the voltage at this pin meets the above mentioned threshold level.
25, 33
PHASE2 and PHASE1 Connect these pins to the sources of the corresponding upper MOSFETs. These pins are
the return path for the upper MOSFET drives.
26, 32
UGATE2 and UGATE1 Connect these pins to the corresponding upper MOSFET gates. These pins are used to
control the upper MOSFETs and are monitored for shoot-through prevention purposes.
Maximum individual channel duty cycle is limited to 93.3%.
27, 31
28, 30
BOOT2 and BOOT1
These pins provide the bias voltage for the corresponding upper MOSFET drives. Connect
these pins to appropriately chosen external bootstrap capacitors. Internal bootstrap
diodes connected to the PVCC1_2 pin provide the necessary bootstrap charge.
LGATE2 and LGATE1 These pins are used to control the lower MOSFETs. Connect these pins to the
corresponding lower MOSFETs’ gates.
29
PVCC1_2
The power supply pin for the multi-phase internal MOSFET drivers. Connect this pin to
any voltage from +5V to +12V depending on the desired MOSFET gate-drive level.
Decouple this pin with a quality 1.0µF ceramic capacitor.
34
PWROK
System wide Power-Good signal. If this pin is low, the two SVI bits are decoded to
determine the “metal VID”. When the pin is high, the SVI is actively running its protocol.
35, 36
PWM3 and PWM4
Pulse-width modulation outputs. Connect these pins to the PWM input pins of an Intersil
driver IC if 3- or 4-phase operation is desired. Connect the ISEN- pins of the channels
not desired to +5V to disable them and configure the core VR controller for 2-phase or
3-phase operation.
37
VDDPWRGD
During normal operation this pin indicates whether both output voltages are within
specified overvoltage and undervoltage limits. If either output voltage exceeds these
limits or a reset event occurs (such as an overcurrent event), the pin is pulled low. This
pin is always low prior to the end of soft-start.
38
PHASE_NB
Connect this pin to the source of the corresponding upper MOSFET. This pin is the return
path for the upper MOSFET drive. This pin is used to monitor the voltage drop across the
upper MOSFET for overcurrent protection.
4
FN9278.5
May 17, 2011
ISL6323
Functional Pin Description (Continued)
PIN NUMBER
SYMBOL
DESCRIPTION
39
UGATE_NB
Connect this pin to the corresponding upper MOSFET gate. This pin provides the PWMcontrolled gate drive for the upper MOSFET and is monitored for shoot-through
prevention purposes.
40
BOOT_NB
This pin provides the bias voltage for the corresponding upper MOSFET drive. Connect
this pin to appropriately chosen external bootstrap capacitor. The internal bootstrap
diode connected to the PVCC_NB pin provides the necessary bootstrap charge.
41
LGATE_NB
Connect this pin to the corresponding MOSFET’s gate. This pin provides the PWMcontrolled gate drive for the lower MOSFET. This pin is also monitored by the adaptive
shoot-through protection circuitry to determine when the lower MOSFET has turned off.
42
PVCC_NB
The power supply pin for the internal MOSFET driver for the Northbridge controller.
Connect this pin to any voltage from +5V to +12V depending on the desired MOSFET
gate-drive level. Decouple this pin with a quality 1.0µF ceramic capacitor.
49
GND
GND is the bias and reference ground for the IC. The GND connection for the ISL6323 is
through the thermal pad on the bottom of the package.
Integrated Driver Block Diagram
PVCC
BOOT
UGATE
PWM
20kΩ
SOFT-START
AND
FAULT LOGIC
GATE
CONTROL
LOGIC
SHOOTTHROUGH
PROTECTION
PHASE
10kΩ
LGATE
5
FN9278.5
May 17, 2011
ISL6323
Controller Block Diagram
RGND_NB
NB_REF
COMP_NB
FB_NB
∑
BOOT_NB
E/A
NB_CS
ISEN_NB+
UV
LOGIC
CURRENT
SENSE
ISEN_NB-
MOSFET
DRIVER
OV
LOGIC
RAMP
PHASE_NB
LGATE_NB
VDDPWRGD
EN_12V
PVCC_NB
APA
APA
NB
FAULT
LOGIC
COMP
OFS
UGATE_NB
ENABLE
LOGIC
EN
VCC
POWER-ON
RESET
OFFSET
PVCC1_2
SOFT-START
AND
FB
FAULT LOGIC
E/A
DVC
RGND
2X
BOOT1
∑
DROOP
CONTROL
LOAD APPLY
TRANSIENT
ENHANCEMENT
PWROK
VID0/VFIXEN
VID1/SEL
VID2/SVD
VID3/SVC
VID4
LGATE1
SVI
SLAVE
BUS
AND
PVI
DAC
CLOCK AND
TRIANGLE WAVE
GENERATOR
FS
PWM1
∑
NB_REF
BOOT2
OV
LOGIC
PWM2
∑
VSEN
UV
LOGIC
ISEN1ISEN2+
ISEN2ISEN3+
ISEN3-
I_TRIP
ISEN4-
I_AVG
∑
EN_12V
CHANNEL
DETECT
CH2
CURRENT
SENSE
CHANNEL
CURRENT
BALANCE
I_AVG
ISEN3ISEN4-
1
N
PWM3
SIGNAL
LOGIC
CH3
CURRENT
SENSE
CH4
CURRENT
SENSE
PHASE2
PH3/PH4
POR
PWM4
CH1
CURRENT
SENSE
UGATE2
LGATE2
∑
OC
RESISTOR
MATCHING
ISEN3-
ISEN4+
MOSFET
DRIVER
PWM3
NB_CS
ISEN1+
UGATE1
PHASE1
VID5
RSET
MOSFET
DRIVER
PWM3
∑
PWM4
SIGNAL
LOGIC
PWM4
ISEN4-
GND
6
FN9278.5
May 17, 2011
ISL6323
Typical Application - SVI Mode
+12V
+12V
FB
COMP
ISEN3+
ISEN3PWM3
VSEN
BOOT1
BOOT1
UGATE1
UGATE1
PHASE1
PHASE1
APA
PWM1
PGND
ISEN1ISEN1+
DVC
+5V
LGATE1
LGATE1
ISL6614
+12V
PVCC1_2
VDD
+12V
VCC
BOOT2
VCC
PVCC
UGATE2
GND
+12V
BOOT2
OFS
UGATE2
FS
CPU
LOAD
PHASE2
PWM2
LGATE2
LGATE2
RSET
NC
NC
PHASE2
VFIXEN
ISEN2SEL
ISEN2+
SVD
SVC
RGND
VID4
VID5
PWROK
VDDPWRGD ISEN4+
GND
ISEN4PWM4
+12V
ISL6323
+12V
PVCC_NB
OFF
EN
BOOT_NB
ON
UGATE_NB
PHASE_NB
VDDNB
LGATE_NB
COMP_NB ISEN_NBFB_NB
NB
LOAD
ISEN_NB+
RGND_NB
7
FN9278.5
May 17, 2011
ISL6323
Typical Application - PVI Mode
+12V
+12V
FB
COMP
ISEN3+
ISEN3PWM3
VSEN
BOOT1
BOOT1
UGATE1
UGATE1
PHASE1
PHASE1
LGATE1
+5V
APA
LGATE1
DVC
ISEN1ISEN1+
PGND
PWM1
ISL6614
+12V
PVCC1_2
VDD
+12V
VCC
+12V
VCC
BOOT2 PVCC
BOOT2
OFS
UGATE2
FS
CPU
LOAD
PHASE2
GND
PHASE2
PWM2
LGATE2
LGATE2
RSET
NC
UGATE2
VID0
ISEN2VID1/SEL
ISEN2+
VID2
VID3
RGND
VID4
VID5
PWROK
VDDPWRGD ISEN4+
GND
ISEN4PWM4
ISL6323
+12V
+12V
NORTH BRIDGE REGULATOR
PVCC_NB
OFF
DISABLED IN PVI MODE
EN
BOOT_NB
ON
UGATE_NB
PHASE_NB
VDDNB
LGATE_NB
COMP_NB ISEN_NB-
FB_NB
NB
LOAD
ISEN_NB+
RGND_NB
8
FN9278.5
May 17, 2011
ISL6323
Absolute Maximum Ratings
Thermal Information
Supply Voltage (VCC) . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +6V
Supply Voltage (PVCC) . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +15V
Absolute Boot Voltage (VBOOT). . . . . . . . GND - 0.3V to GND + 36V
Phase Voltage (VPHASE) . . . . . . . GND - 0.3V to 24V (PVCC = 12V)
GND - 8V (<400ns, 20µJ) to 31V (<200ns, VBOOT-PHASE = 5V)
Upper Gate Voltage (VUGATE). . . . VPHASE - 0.3V to VBOOT + 0.3V
VPHASE - 3.5V (<100ns Pulse Width, 2µJ) to VBOOT + 0.3V
Lower Gate Voltage (VLGATE) . . . . . . . GND - 0.3V to PVCC + 0.3V
GND - 5V (<100ns Pulse Width, 2µJ) to PVCC+ 0.3V
Input, Output, or I/O Voltage . . . . . . . . . GND - 0.3V to VCC + 0.3V
Thermal Resistance
θJA (°C/W)
θJC (°C/W)
QFN Package (Notes 1, 2) . . . . . . . . . .
27
2
Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . +150°C
Maximum Storage Temperature Range . . . . . . . . . .-65°C to +150°C
Pb-free reflow profile . . . . . . . . . . . . . . . . . . . . . . . . . .see link below
http://www.intersil.com/pbfree/Pb-FreeReflow.asp
Recommended Operating Conditions
VCC Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+5V ±5%
PVCC Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . +5V to 12V ±5%
Ambient Temperature
ISL6323CRZ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to +70°C
ISL6323IRZ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-40°C to +85°C
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product reliability and
result in failures not covered by warranty.
NOTES:
1. θJA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See
Tech Brief TB379.
2. For θJC, the “case temp” location is the center of the exposed metal pad on the package underside.
Electrical Specifications
Recommended Operating Conditions (0°C to +70°C), Unless Otherwise Specified.
PARAMETER
TEST CONDITIONS
MIN
(Note 3)
TYP
MAX
(Note 3)
UNITS
BIAS SUPPLIES
Input Bias Supply Current
IVCC; EN = high
15
22
30
mA
Gate Drive Bias Current - PVCC1_2 Pin
IPVCC1_2; EN = high
1
1.8
3
mA
Gate Drive Bias Current - PVCC_NB Pin
IPVCC_NB; EN = high
0.3
0.9
2
mA
VCC POR (Power-On Reset) Threshold
VCC Rising
4.20
4.40
4.55
V
VCC Falling
3.70
3.90
4.10
V
PVCC Rising
4.20
4.40
4.55
V
PVCC Falling
3.70
3.90
4.10
V
RT = 100kΩ (±0.1%) to Ground, TA = +25°C
(Droop Enabled)
225
250
275
kHz
RT = 100kΩ (±0.1%) to VCC, TA = +25°C
(Droop Disabled)
240
270
300
kHz
Typical Adjustment Range of Switching Frequency
(Note 4)
0.08
1.0
MHz
Oscillator Ramp Amplitude, VP-P
(Note 4)
PVCC POR (Power-On Reset) Threshold
PWM MODULATOR
Oscillator Frequency Accuracy, fSW
1.50
V
CONTROL THRESHOLDS
EN Rising Threshold
EN Hysteresis
0.80
0.88
0.92
V
70
130
190
mV
PWROK Input HIGH Threshold
1.1
V
PWROK Input LOW Threshold
0.95
V
VDDPWRGD Sink Current
Open drain, V_VDDPWRGD = 400mV
4
mA
PWM Channel Disable Threshold
VISEN3-, VISEN4-
4.4
OFS Source Current Accuracy (Positive Offset)
ROFS = 10kΩ (±0.1%) from OFS to GND
27.5
31
34.5
µA
OFS Sink Current Accuracy (Negative Offset)
ROFS = 30kΩ (±0.1%) from OFS to VCC
50.5
53.5
56.5
µA
V
PIN_ADJUSTABLE OFFSET
9
FN9278.5
May 17, 2011
ISL6323
Electrical Specifications
Recommended Operating Conditions (0°C to +70°C), Unless Otherwise Specified. (Continued)
PARAMETER
TEST CONDITIONS
MIN
(Note 3)
TYP
MAX
(Note 3)
UNITS
REFERENCE AND DAC
System Accuracy (VDAC > 1.000V)
-0.6
0.6
%
System Accuracy (0.600V < VDAC < 1.000V)
-1.0
1.0
%
System Accuracy (VDAC < 0.600V)
-2.0
2.0
%
DVC Voltage Gain
VDAC = 1V
APA Current Tolerance
VAPA = 1V
2.0
90
100
V
108
µA
ERROR AMPLIFIER
DC Gain
RL = 10k to ground, (Note 4)
96
dB
Gain-Bandwidth Product (Note 4)
CL = 100pF, RL = 10k to ground, (Note 4)
20
MHz
Slew Rate (Note 4)
CL = 100pF, Load = ±400µA, (Note 4)
8
V/µs
Maximum Output Voltage
Load = 1mA
4.20
V
Minimum Output Voltage
Load = -1mA
3.80
1.3
1.6
V
3.0
4.0
mV/µs
0.5
V
SOFT-START RAMP
Soft-Start Ramp Rate
2.2
PWM OUTPUTS
PWM Output Voltage LOW Threshold
ILOAD = ±500µA
PWM Output Voltage HIGH Threshold
ILOAD = ±500μA
4.5
V
CURRENT SENSING - CORE CONTROLLER
Current Sense Resistance, RISEN (Internal)
(Note 4)
TA = +25°C
Average Sensed and Droop Current Tolerance
ISEN1+ = ISEN2+ = ISEN3+ = ISEN4+ = 77µA
Ω
2400
68
77
87
µA
CURRENT SENSING - NB CONTROLLER
Current Sense Resistance, RISEN_NB (Internal)
(Note 4)
TA = +25°C
Sensed Current Tolerance
ISEN_NB = 80µA
2400
Ω
80
µA
OVERCURRENT PROTECTION
Overcurrent Trip Level - Average Channel
Overcurrent Trip Level - Individual Channel
Normal Operation
83
100
111
µA
Dynamic VID Change (Note 4)
130
µA
Normal Operation
142
µA
Dynamic VID Change (Note 4)
190
µA
POWER GOOD
Overvoltage Threshold
VSEN Rising (Core and North Bridge)
VDAC
+225mV
VDAC +
250mV
VDAC +
275mV
V
Undervoltage Threshold
VSEN Falling (Core)
VDAC 325mV
VDAC 300mV
VDAC 275mV
mV
VSEN Falling (North Bridge)
VDAC 310mV
VDAC 275mV
VDAC 245mV
mV
Power Good Hysteresis
50
mV
OVERVOLTAGE PROTECTION
OVP Trip Level
1.73
1.80
OVP Lower Gate Release Threshold
350
400
10
1.84
V
mV
FN9278.5
May 17, 2011
ISL6323
Electrical Specifications
Recommended Operating Conditions (0°C to +70°C), Unless Otherwise Specified. (Continued)
PARAMETER
MIN
(Note 3)
TEST CONDITIONS
TYP
MAX
(Note 3)
UNITS
SWITCHING TIME (Note 4) [See “Timing Diagram” on page 11]
UGATE Rise Time
tRUGATE; VPVCC = 12V, 3nF Load, 10% to 90%
26
ns
LGATE Rise Time
tRLGATE; VPVCC = 12V, 3nF Load, 10% to 90%
18
ns
UGATE Fall Time
tFUGATE; VPVCC = 12V, 3nF Load, 90% to 10%
18
ns
LGATE Fall Time
tFLGATE; VPVCC = 12V, 3nF Load, 90% to 10%
12
ns
UGATE Turn-On Non-overlap
tPDHUGATE; VPVCC = 12V, 3nF Load, Adaptive
10
ns
LGATE Turn-On Non-overlap
tPDHLGATE; VPVCC = 12V, 3nF Load, Adaptive
10
ns
Upper Drive Source Resistance
VPVCC = 12V, 15mA Source Current
2.0
Ω
Upper Drive Sink Resistance
VPVCC = 12V, 15mA Sink Current
1.65
Ω
Lower Drive Source Resistance
VPVCC = 12V, 15mA Source Current
1.25
Ω
Lower Drive Sink Resistance
VPVCC = 12V, 15mA Sink Current
0.80
Ω
GATE DRIVE RESISTANCE (Note 4)
MODE SELECTION
VID1/SEL Input Low
EN taken from HI to LO, VDDIO = 1.5V
VID1/SEL Input High
EN taken from LO to HI, VDDIO = 1.5V
0.45
1.00
V
V
PVI INTERFACE
VIDx Pull-down
VDDIO = 1.5V
VIDx Input Low
VDDIO = 1.5V
VIDx Input High
VDDIO = 1.5V
30
45
µA
0.45
V
1.00
V
SVI INTERFACE
SVC, SVD Input LOW (VIL)
SVC, SVD Input HIGH (VIH)
1.10
Schmitt Trigger Input Hysteresis
0.14
SVD Low Level Output Voltage
V
0.55
V
0.285
V
V
0.35
3mA Sink Current
Maximum SVC, SVD Leakage (Note 4)
0.4
±5
µA
NOTES:
3. Parameters with MIN and/or MAX limits are 100% tested at +25°C, unless otherwise specified. Temperature limits established by characterization
and are not production tested.
4. Limits should be considered typical and are not production tested.
Timing Diagram
tPDHUGATE
tRUGATE
tFUGATE
UGATE
LGATE
tFLGATE
tRLGATE
tPDHLGATE
11
FN9278.5
May 17, 2011
ISL6323
Operation
The ISL6323 utilizes a multiphase architecture to provide a
low cost, space saving power conversion solution for the
processor core voltage. The controller also implements a
simple single phase architecture to provide the Northbridge
voltage on the same chip.
Multiphase Power Conversion
Microprocessor load current profiles have changed to the
point that the advantages of multiphase power conversion
are impossible to ignore. The technical challenges
associated with producing a single-phase converter that is
both cost-effective and thermally viable have forced a
change to the cost-saving approach of multiphase. The
ISL6323 controller helps simplify implementation by
integrating vital functions and requiring minimal external
components. The “Controller Block Diagram” on page 6
provides a top level view of the multiphase power conversion
using the ISL6323 controller.
Interleaving
The switching of each channel in a multiphase converter is
timed to be symmetrically out-of-phase with each of the other
channels. In a 3-phase converter, each channel switches 1/3
cycle after the previous channel and 1/3 cycle before the
following channel. As a result, the 3-phase converter has a
combined ripple frequency 3x greater than the ripple frequency
of any one phase. In addition, the peak-to-peak amplitude of
the combined inductor currents is reduced in proportion to the
number of phases (Equations 2 and 3). Increased ripple
frequency and lower ripple amplitude mean that the designer
can use less per-channel inductance and lower total output
capacitance for any performance specification.
Figure 1 illustrates the multiplicative effect on output ripple
frequency. The 3-channel currents (IL1, IL2, and IL3)
combine to form the AC ripple current and the DC load
current. The ripple component has 3x the ripple frequency of
each individual channel current. Each PWM pulse is
terminated 1/3 of a cycle after the PWM pulse of the previous
phase. The peak-to-peak current for each phase is about 7A,
and the DC components of the inductor currents combine to
feed the load.
To understand the reduction of ripple current amplitude in the
multiphase circuit, examine the equation representing an
individual channel peak-to-peak inductor current.
( V IN – V OUT ) V OUT
I P – P = ----------------------------------------------------L fS V
(EQ. 2)
expression for the peak-to-peak current after the summation
of N symmetrically phase-shifted inductor currents in
Equation 3. Peak-to-peak ripple current decreases by an
amount proportional to the number of channels. Output
voltage ripple is a function of capacitance, capacitor
equivalent series resistance (ESR), and inductor ripple
current. Reducing the inductor ripple current allows the
designer to use fewer or less costly output capacitors.
( V IN – N V OUT ) V OUT
I C ( P-P ) = ----------------------------------------------------------L fS V
(EQ. 3)
IN
Another benefit of interleaving is to reduce input ripple
current. Input capacitance is determined in part by the
maximum input ripple current. Multiphase topologies can
improve overall system cost and size by lowering input ripple
current and allowing the designer to reduce the cost of input
capacitance. The example in Figure 2 illustrates input
currents from a 3-phase converter combining to reduce the
total input ripple current.
The converter depicted in Figure 2 delivers 1.5V to a 36A load
from a 12V input. The RMS input capacitor current is 5.9A.
Compare this to a single-phase converter also stepping down
12V to 1.5V at 36A. The single-phase converter has
11.9ARMS input capacitor current. The single-phase converter
must use an input capacitor bank with twice the RMS current
capacity as the equivalent 3-phase converter.
Figures 25, 26 and 27 in the section entitled “Input Capacitor
Selection” on page 32 can be used to determine the input
capacitor RMS current based on load current, duty cycle,
and the number of channels. They are provided as aids in
determining the optimal input capacitor solution.
IL1 + IL2 + IL3, 7A/DIV
IL3, 7A/DIV
PWM3, 5V/DIV
IL2, 7A/DIV
PWM2, 5V/DIV
IL1, 7A/DIV
PWM1, 5V/DIV
1µs/DIV
FIGURE 1. PWM AND INDUCTOR-CURRENT WAVEFORMS
FOR 3-PHASE CONVERTER
IN
In Equation 2, VIN and VOUT are the input and output
voltages respectively, L is the single-channel inductor value,
and fS is the switching frequency.
The output capacitors conduct the ripple component of the
inductor current. In the case of multiphase converters, the
capacitor current is the sum of the ripple currents from each
of the individual channels. Compare Equation 2 to the
12
FN9278.5
May 17, 2011
ISL6323
INPUT-CAPACITOR CURRENT, 10A/DIV
CHANNEL 3
INPUT CURRENT
10A/DIV
CHANNEL 2
INPUT CURRENT
10A/DIV
CHANNEL 1
INPUT CURRENT
10A/DIV
1μs/DIV
FIGURE 2. CHANNEL INPUT CURRENTS AND INPUT
CAPACITOR RMS CURRENT FOR 3-PHASE
CONVERTER
To further improve the transient response, ISL6323 also
implements Intersil’s proprietary Adaptive Phase Alignment
(APA) technique, which turns on all phases together under
transient events with large step current. With both APP and
APA control, ISL6323 can achieve excellent transient
performance and reduce the demand on the output capacitors.
Adaptive Phase Alignment (APA)
To further improve the transient response, the ISL6323 also
implements Intersil’s proprietary Adaptive Phase Alignment
(APA) technique, which turns on all of the channels together
at the same time during large current step transient events.
As Figure 3 shows, the APA circuitry works by monitoring the
voltage on the APA pin and comparing it to a filtered copy of
the voltage on the COMP pin. The voltage on the APA pin is
a copy of the COMP pin voltage that has been negatively
offset. If the APA pin exceeds the filtered COMP pin voltage
an APA event occurs and all of the channels are forced on.
Active Pulse Positioning Modulated PWM Operation
During each PWM time interval the PWM signal can only
transition high once. Once PWM transitions high it can not
transition high again until the beginning of the next PWM
time interval. This prevents the occurrence of double PWM
pulses occurring during a single period.
13
ISL6323 INTERNAL CIRCUIT
APA
CAPA
RAPA
-
The PWM output state is driven by the position of the error
amplifier output signal, VCOMP, minus the current correction
signal relative to the proprietary modulator ramp waveform as
illustrated in Figure 3. At the beginning of each PWM time
interval, this modified VCOMP signal is compared to the
internal modulator waveform. As long as the modified VCOMP
voltage is lower then the modulator waveform voltage, the
PWM signal is commanded low. The internal MOSFET driver
detects the low state of the PWM signal and turns off the
upper MOSFET and turns on the lower synchronous
MOSFET. When the modified VCOMP voltage crosses the
modulator ramp, the PWM output transitions high, turning off
the synchronous MOSFET and turning on the upper
MOSFET. The PWM signal will remain high until the modified
VCOMP voltage crosses the modulator ramp again. When this
occurs the PWM signal will transition low again.
EXTERNAL CIRCUIT
100µA
VAPA,TRIP
+
-
+
LOW
PASS
FILTER
COMP
APA
TO APA
CIRCUITRY
+
ERROR
AMPLIFIER
-
The ISL6323 uses a proprietary Active Pulse Positioning (APP)
modulation scheme to control the internal PWM signals that
command each channel’s driver to turn their upper and lower
MOSFETs on and off. The time interval in which a PWM signal
can occur is generated by an internal clock, whose cycle time is
the inverse of the switching frequency set by the resistor
between the FS pin and ground. The advantage of Intersil’s
proprietary Active Pulse Positioning (APP) modulator is that the
PWM signal has the ability to turn on at any point during this
PWM time interval, and turn off immediately after the PWM
signal has transitioned high. This is important because it allows
the controller to quickly respond to output voltage drops
associated with current load spikes, while avoiding the ring
back affects associated with other modulation schemes.
FIGURE 3. ADAPTIVE PHASE ALIGNMENT DETECTION
The APA trip level is the amount of DC offset between the
COMP pin and the APA pin. This is the voltage excursion
that the APA and COMP pins must have during a transient
event to activate the Adaptive Phase Alignment circuitry.
This APA trip level is set through a resistor, RAPA, that
connects from the APA pin to the COMP pin. A 100µA
current flows across RAPA into the APA pin to set the APA
trip level as described in Equation 4. An APA trip level of
500mV is recommended for most applications. A 0.1µF
capacitor, CAPA, should also be placed across the RAPA
resistor to help with noise immunity.
V APA, TRIP = R APA ⋅ 100 × 10
–6
(EQ. 4)
PWM Operation
The timing of each core channel is set by the number of
active channels. Channel detection on the ISEN3- and
ISEN4- pins selects 2-channel to 4-channel operation for the
ISL6323. The switching cycle is defined as the time between
PWM pulse termination signals of each channel. The cycle
time of the pulse signal is the inverse of the switching
frequency set by the resistor between the FS pin and
FN9278.5
May 17, 2011
ISL6323
Connecting ISEN4- to VCC selects 3-channel operation and
the pulse times are spaced in 1/3 cycle increments. If ISEN3- is
connected to VCC, 2-channel operation is selected and the
PWM2 pulse happens 1/2 of a cycle after PWM1 pulse.
s⋅L
⎛ ------------+ 1⎞
⎝ DCR
⎠
V C ( s ) = -------------------------------------------------------- ⋅ K ⋅ DCR ⋅ I L
n
⎛ ( R1 ⋅ R2 )
⎞
⎜ s ⋅ ------------------------ ⋅ C + 1⎟
R
+
R
⎝
⎠
1
2
Where:
R2
K = --------------------R2 + R1
(EQ. 7)
I
VIN
Continuous Current Sampling
L
n
UGATE(n)
L
MOSFET
LGATE(n)
VOUT
INDUCTOR
+
DRIVER
DCR
VL(s)
+
In order to realize proper current-balance, the currents in
each channel are sampled continuously every switching
cycle. During this time, the current-sense amplifier uses the
ISEN inputs to reproduce a signal proportional to the
inductor current, IL. This sensed current, ISEN, is simply a
scaled version of the inductor current.
(EQ. 6)
VC(s)
R1
COUT
-
For 4-channel operation, the channel firing order is 4-3-2-1:
PWM3 pulse happens 1/4 of a cycle after PWM4, PWM2
output follows another 1/4 of a cycle after PWM3, and
PWM1 delays another 1/4 of a cycle after PWM2. For
3-channel operation, the channel firing order is 3-2-1.
across the sense capacitor, VC, can be shown to be
proportional to the channel current ILn, shown in Equation 6.
-
ground. The PWM signals command the MOSFET driver to
turn on/off the channel MOSFETs.
C
R2
ISL6323 INTERNAL CIRCUIT
In
PWM
SWITCHING PERIOD
SAMPLE
IL
-
VC(s)
RISEN
ISEN
ISEN
TO ACTIVE
CORE CHANNELS
The ISL6323 supports Inductor DCR current sensing to
continuously sample each channel’s current for channel-current
balance. The internal circuitry, shown in Figure 5 represents
Channel N of an N-Channel converter. This circuitry is repeated
for each channel in the converter, but may not be active
depending on how many channels are operating.
Inductor windings have a characteristic distributed
resistance or DCR (Direct Current Resistance). For
simplicity, the inductor DCR is considered as a separate
lumped quantity, as shown in Figure 5. The channel current
ILn, flowing through the inductor, passes through the DCR.
Equation 5 shows the S-domain equivalent voltage, VL,
across the inductor.
(EQ. 5)
n
A simple R-C network across the inductor (R1, R2 and C)
extracts the DCR voltage, as shown in Figure 6. The voltage
14
ISENn+
{
RSET
RSET
CSET
FIGURE 4. CONTINUOUS CURRENT SAMPLING
V L ( s ) = I L ⋅ ( s ⋅ L + DCR )
ISENn-
VCC
TO NORTH BRIDGE
TIME
-
+
+
FIGURE 5. INDUCTOR DCR CURRENT SENSING
CONFIGURATION
If the R-C network components are selected such that the
RC time constant matches the inductor L/DCR time constant
(see Equation 8), then VC is equal to the voltage drop across
the DCR multiplied by the ratio of the resistor divider, K. If a
resistor divider is not being used, the value for K is 1.
R1 ⋅ R2
L
-⋅C
------------- = -------------------R1 + R2
DCR
(EQ. 8)
The capacitor voltage VC, is then replicated across the effective
internal sense resistor, RISEN. This develops a current through
RISEN which is proportional to the inductor current. This
current, ISEN, is continuously sensed and is then used by the
controller for load-line regulation, channel-current balancing,
and overcurrent detection and limiting. Equation 9 shows that
the proportion between the channel current, IL, and the sensed
current, ISEN, is driven by the value of the effective sense
resistance, RISEN, and the DCR of the inductor.
FN9278.5
May 17, 2011
ISL6323
.
DCR
I SEN = I L ⋅ -----------------R ISEN
(EQ. 9)
The effective internal RISEN resistance is important to the
current sensing process because it sets the gain of the load
line regulation loop when droop is enabled as well as the
gain of the channel-current balance loop and the overcurrent
trip level. The effective internal RISEN resistance is user
programmable and is set through use of the RSET pin.
Placing a single resistor, RSET, from the RSET pin to the
VCC pin programs the effective internal RISEN resistance
according to Equation 10.
3
R ISEN = ---------- ⋅ R SET
400
(EQ. 10)
The North Bridge regulator samples the load current in the
same manner as the Core regulator does. The RSET resistor
will program all the effective internal RISEN resistors to the
same value.
Channel-Current Balance
One important benefit of multiphase operation is the thermal
advantage gained by distributing the dissipated heat over
multiple devices and greater area. By doing this the designer
avoids the complexity of driving parallel MOSFETs and the
expense of using expensive heat sinks and exotic magnetic
materials.
VCOMP
+
MODULATOR
RAMP
WAVEFORM
FILTER
+
PWM1
-
TO GATE
CONTROL
LOGIC
f(s)
I4
IER
IAVG
-
+
Σ
÷N
I3
I2
I1
NOTE: Channel 3 and 4 are optional.
FIGURE 6. CHANNEL-1 PWM FUNCTION AND CURRENTBALANCE ADJUSTMENT
In order to realize the thermal advantage, it is important that
each channel in a multiphase converter be controlled to
carry about the same amount of current at any load level. To
achieve this, the currents through each channel must be
sampled every switching cycle. The sampled currents, In,
from each active channel are summed together and divided
by the number of active channels. The resulting cycle
average current, IAVG, provides a measure of the total load
current demand on the converter during each switching
cycle. Channel-current balance is achieved by comparing
the sampled current of each channel to the cycle average
current, and making the proper adjustment to each channel
pulse width based on the error. Intersil’s patented current
balance method is illustrated in Figure 6, with error
15
correction for Channel 1 represented. In the figure, the cycle
average current, IAVG, is compared with the Channel 1
sample, I1, to create an error signal IER.
The filtered error signal modifies the pulse width
commanded by VCOMP to correct any unbalance and force
IER toward zero. The same method for error signal
correction is applied to each active channel.
VID Interface
The ISL6323 supports hybrid power control of AMD
processors which operate from either a 6-bit parallel VID
interface (PVI) or a serial VID interface (SVI). The VID1/SEL
pin is used to command the ISL6323 into either the PVI
mode or the SVI mode. Whenever the EN pin is held LOW,
both the multiphase Core and single-phase North Bridge
Regulators are disabled and the ISL6323 is continuously
sampling voltage on the VID1/SEL pin. When the EN pin is
toggled HIGH, the status of the VID1/SEL pin will latch the
ISL6323 into either PVI or SVI mode. This latching occurs on
the rising edge of the EN signal.If the VID1/SEL pin is held
LOW during the latch, the ISL6323 will be placed into SVI
mode. If the VID1/SEL pin is held HIGH during the latch, the
ISL6323 will be placed into PVI mode. For the ISL6323 to
properly enter into either mode, the level on the VID1/SEL
pin must be stable no less that 1µs prior to the EN signal
transitioning from low to high.
6-Bit Parallel VID Interface (PVI)
With the ISL6323 in PVI mode, the single-phase North
Bridge regulator is disabled. Only the multiphase controller is
active in PVI mode to support uniplane VDD only
processors. Table 1 shows the 6-bit parallel VID codes and
the corresponding reference voltage.
TABLE 1. 6-BIT PARALLEL VID CODES
VID5
VID4
VID3
VID2
VID1
VID0
VREF
0
0
0
0
0
0
1.5500
0
0
0
0
0
1
1.5250
0
0
0
0
1
0
1.5000
0
0
0
0
1
1
1.4750
0
0
0
1
0
0
1.4500
0
0
0
1
0
1
1.4250
0
0
0
1
1
0
1.4000
0
0
0
1
1
1
1.3750
0
0
1
0
0
0
1.3500
0
0
1
0
0
1
1.3250
0
0
1
0
1
0
1.3000
0
0
1
0
1
1
1.2750
0
0
1
1
0
0
1.2500
0
0
1
1
0
1
1.2250
0
0
1
1
1
0
1.2000
0
0
1
1
1
1
1.1750
FN9278.5
May 17, 2011
ISL6323
TABLE 1. 6-BIT PARALLEL VID CODES (Continued)
TABLE 1. 6-BIT PARALLEL VID CODES (Continued)
VID5
VID4
VID3
VID2
VID1
VID0
VREF
VID5
VID4
VID3
VID2
VID1
VID0
VREF
0
1
0
0
0
0
1.1500
1
0
1
1
0
1
0.6000
0
1
0
0
0
1
1.1250
1
0
1
1
1
0
0.5875
0
1
0
0
1
0
1.1000
1
0
1
1
1
1
0.5750
0
1
0
0
1
1
1.0750
1
1
0
0
0
0
0.5625
0
1
0
1
0
0
1.0500
1
1
0
0
0
1
0.5500
0
1
0
1
0
1
1.0250
1
1
0
0
1
0
0.5375
0
1
0
1
1
0
1.0000
1
1
0
0
1
1
0.5250
0
1
0
1
1
1
0.9750
1
1
0
1
0
0
0.5125
0
1
1
0
0
0
0.9500
1
1
0
1
0
1
0.5000
0
1
1
0
0
1
0.9250
1
1
0
1
1
0
0.4875
0
1
1
0
1
0
0.9000
1
1
0
1
1
1
0.4750
0
1
1
0
1
1
0.8750
1
1
1
0
0
0
0.4625
0
1
1
1
0
0
0.8500
1
1
1
0
0
1
0.4500
0
1
1
1
0
1
0.8250
1
1
1
0
1
0
0.4375
0
1
1
1
1
0
0.8000
1
1
1
0
1
1
0.4250
0
1
1
1
1
1
0.7750
1
1
1
1
0
0
0.4125
1
0
0
0
0
0
0.7625
1
1
1
1
0
1
0.4000
1
0
0
0
0
1
0.7500
1
1
1
1
1
0
0.3875
1
0
0
0
1
0
0.7375
1
1
1
1
1
1
0.3750
1
0
0
0
1
1
0.7250
1
0
0
1
0
0
0.7125
1
0
0
1
0
1
0.7000
1
0
0
1
1
0
0.6875
1
0
0
1
1
1
0.6750
1
0
1
0
0
0
0.6625
1
0
1
0
0
1
0.6500
1
0
1
0
1
0
0.6375
1
0
1
0
1
1
0.6250
1
0
1
1
0
0
0.6125
1
2
3
4
Serial VID Interface (SVI)
The on-board Serial VID interface (SVI) circuitry allows the
processor to directly drive the core voltage and Northbridge
voltage reference level within the ISL6323. The SVC and SVD
states are decoded with direction from the PWROK and
VFIXEN inputs as described in the following sections. The
ISL6323 uses a digital to analog converter (DAC) to generate a
reference voltage based on the decoded SVI value. See
Figure 7 for a simple SVI interface timing diagram.
5
6
7
8
9
V_SVI
METAL_VID
10
11
12
VCC
SVC
SVD
ENABLE
PWROK
METAL_VID
VDD AND VDDNB
V_SVI
VDDPWRGD
VFIXEN
FIGURE 7. SVI INTERFACE TIMING DIAGRAM: TYPICAL PRE-PWROK METAL VID START-UP
16
FN9278.5
May 17, 2011
ISL6323
PRE-PWROK METAL VID
Typical motherboard start-up occurs with the VFIXEN input
low. The controller decodes the SVC and SVD inputs to
determine the Pre-PWROK metal VID setting. Once the
POR circuitry is satisfied, the ISL6323 begins decoding the
inputs per Table 2. Once the EN input exceeds the rising
enable threshold, the ISL6323 saves the Pre-PWROK metal
VID value in an on-board holding register and passes this
target to the internal DAC circuitry.
internal soft-start circuitry slowly stair steps the reference up
to the target value and this results in a controlled ramp of the
power planes. Once soft-start has ended and both output
planes are within regulation limits, the VDDPWRGD pin
transitions high. If the EN input falls below the enable falling
threshold, then the controller ramps both VDD and VDDNB
down to near zero.
TABLE 3. VFIXEN VID CODES
SVC
SVD
OUTPUT VOLTAGE (V)
TABLE 2. PRE-PWROK METAL VID CODES
0
0
1.4
SVC
SVD
OUTPUT VOLTAGE (V)
0
1
1.2
0
0
1.1
1
0
1.0
0
1
1.0
1
1
0.8
1
0
0.9
1
1
0.8
SVI MODE
The Pre-PWROK metal VID code is decoded and latched on
the rising edge of the enable signal. Once enabled, the
ISL6323 passes the Pre-PWROK metal VID code on to
internal DAC circuitry. The internal DAC circuitry begins to
ramp both the VDD and VDDNB planes to the decoded
Pre-PWROK metal VID output level. The digital soft-start
circuitry actually stair steps the internal reference to the
target gradually over a fix interval. The controlled ramp of
both output voltage planes reduces in-rush current during
the soft-start interval. At the end of the soft-start interval, the
VDDPWRGD output transitions high indicating both output
planes are within regulation limits.
If the EN input falls below the enable falling threshold, the
ISL6323 ramps the internal reference voltage down to near
zero. The VDDPWRGD de-asserts with the loss of enable.
The VDD and VDDNB planes will linearly decrease to near
zero.
VFIX MODE
In VFIX Mode, the SVC, SVD and VFIXEN inputs are fixed
external to the controller through jumpers to either GND or
VDDIO. These inputs are not expected to change, but the
ISL6323 is designed to support the potential change of state
of these inputs. If VFIXEN is high, the IC decodes the SVC
and SVD states per Table 3.
Once enabled, the ISL6323 begins to soft-start both VDD
and VDDNB planes to the programmed VFIX level. The
Once the controller has successfully soft-started and
VDDPWRGD transitions high, the Northbridge SVI interface
can assert PWROK to signal the ISL6323 to prepare for SVI
commands. The controller actively monitors the SVI
interface for set VID commands to move the plane voltages
to start-up VID values. Details of the SVI Bus protocol are
provided in the AMD Design Guide for Voltage Regulator
Controllers Accepting Serial VID Codes specification.
Once the set VID command is received, the ISL6323
decodes the information to determine which plane and the
VID target required. See Table 4. The internal DAC circuitry
steps the required output plane voltage to the new VID level.
During this time one or both of the planes could be targeted.
In the event the core voltage plane, VDD, is commanded to
power off by serial VID commands, the VDDPWRGD signal
remains asserted. The Northbridge voltage plane must
remain active during this time.
If the PWROK input is de-asserted, then the controller steps
both VDD and VDDNB planes back to the stored
Pre-PWROK metal VID level in the holding register from
initial soft-start. No attempt is made to read the SVC and
SVD inputs during this time. If PWROK is reasserted, then
the on-board SVI interface waits for a set VID command.
If VDDPWRGD deasserts during normal operation, both
voltage planes are powered down in a controlled fashion.
The internal DAC circuitry stair steps both outputs down to
near zero.
TABLE 4. SERIAL VID CODES
SVID[6:0]
VOLTAGE (V)
SVID[6:0]
VOLTAGE (V)
SVID[6:0]
VOLTAGE (V)
SVID[6:0]
VOLTAGE (V)
000_0000b
1.5500
010_0000b
1.1500
100_0000b
0.7500
110_0000b
0.3500*
000_0001b
1.5375
010_0001b
1.1375
100_0001b
0.7375
110_0001b
0.3375*
000_0010b
1.5250
010_0010b
1.1250
100_0010b
0.7250
110_0010b
0.3250*
000_0011b
1.5125
010_0011b
1.1125
100_0011b
0.7125
110_0011b
0.3125*
000_0100b
1.5000
010_0100b
1.1000
100_0100b
0.7000
110_0100b
0.3000*
000_0101b
1.4875
010_0101b
1.0875
100_0101b
0.6875
110_0101b
0.2875*
17
FN9278.5
May 17, 2011
ISL6323
TABLE 4. SERIAL VID CODES (Continued)
SVID[6:0]
000_0110b
VOLTAGE (V)
1.4750
SVID[6:0]
010_0110b
VOLTAGE (V)
1.0750
SVID[6:0]
100_0110b
VOLTAGE (V)
0.6750
SVID[6:0]
110_0110b
VOLTAGE (V)
0.2750*
000_0111b
1.4625
010_0111b
1.0625
100_0111b
0.6625
110_0111b
0.2625*
000_1000b
1.4500
010_1000b
1.0500
100_1000b
0.6500
110_1000b
0.2500*
000_1001b
1.4375
010_1001b
1.0375
100_1001b
0.6375
110_1001b
0.2375*
000_1010b
1.4250
010_1010b
1.0250
100_1010b
0.6250
110_1010b
0.2250*
000_1011b
1.4125
010_1011b
1.0125
100_1011b
0.6125
110_1011b
0.2125*
000_1100b
1.4000
010_1100b
1.0000
100_1100b
0.6000
110_1100b
0.2000*
000_1101b
1.3875
010_1101b
0.9875
100_1101b
0.5875
110_1101b
0.1875*
000_1110b
1.3750
010_1110b
0.9750
100_1110b
0.5750
110_1110b
0.1750*
000_1111b
1.3625
010_1111b
0.9625
100_1111b
0.5625
110_1111b
0.1625*
001_0000b
1.3500
011_0000b
0.9500
101_0000b
0.5500
111_0000b
0.1500*
001_0001b
1.3375
011_0001b
0.9375
101_0001b
0.5375
111_0001b
0.1375*
001_0010b
1.3250
011_0010b
0.9250
101_0010b
0.5250
111_0010b
0.1250*
001_0011b
1.3125
011_0011b
0.9125
101_0011b
0.5125
111_0011b
0.1125*
001_0100b
1.3000
011_0100b
0.9000
101_0100b
0.5000
111_0100b
0.1000*
001_0101b
1.2875
011_0101b
0.8875
101_0101b
0.4875*
111_0101b
0.0875*
001_0110b
1.2750
011_0110b
0.8750
101_0110b
0.4750*
111_0110b
0.0750*
001_0111b
1.2625
011_0111b
0.8625
101_0111b
0.4625*
111_0111b
0.0625*
001_1000b
1.2500
011_1000b
0.8500
101_1000b
0.4500*
111_1000b
0.0500*
001_1001b
1.2375
011_1001b
0.8375
101_1001b
0.4375*
111_1001b
0.0375*
001_1010b
1.2250
011_1010b
0.8250
101_1010b
0.4250*
111_1010b
0.0250*
001_1011b
1.2125
011_1011b
0.8125
101_1011b
0.4125*
111_1011b
0.0125*
001_1100b
1.2000
011_1100b
0.8000
101_1100b
0.4000*
111_1100b
OFF
001_1101b
1.1875
011_1101b
0.7875
101_1101b
0.3875*
111_1101b
OFF
001_1110b
1.1750
011_1110b
0.7750
101_1110b
0.3750*
111_1110b
OFF
001_1111b
1.1625
011_1111b
0.7625
101_1111b
0.3625*
111_1111b
OFF
NOTE: * Indicates a VID not required for AMD Family 10h processors.
Voltage Regulation
The integrating compensation network shown in Figure 8
insures that the steady-state error in the output voltage is
limited only to the error in the reference voltage and offset
errors in the OFS current source, remote-sense and error
amplifiers. Intersil specifies the guaranteed tolerance of the
ISL6323 to include the combined tolerances of each of these
elements.
The ISL6323 incorporates differential remote-sense
amplification in the feedback path. The differential sensing
removes the voltage error encountered when measuring the
output voltage relative to the controller ground reference point
resulting in a more accurate means of sensing output voltage.
The output of the error amplifier, VCOMP, is used by the
modulator to generate the PWM signals. The PWM signals
control the timing of the Internal MOSFET drivers and
regulate the converter output so that the voltage at FB is equal
to the voltage at REF. This will regulate the output voltage to
be equal to Equation 11. The internal and external circuitry
that controls voltage regulation is illustrated in Figure 8.
V OUT = V REF – V OFS – V DROOP
18
(EQ. 11)
FN9278.5
May 17, 2011
ISL6323
.
EXTERNAL CIRCUIT
ISL6323 INTERNAL CIRCUIT
FS
RFS
DROOP
CONTROL
TO
OSCILLATOR
COMP
CC
IAVG
IOFS
+
RFB
+
VOUT
-
VCOMP
ERROR
AMPLIFIER
+
(VDROOP + VOFS)
-
∑
VSEN
+
+
Where, VREF is the reference voltage, VOFS is the
programmed offset voltage, IOUT is the total output current
of the converter, K is the DC gain of the RC filter across the
inductor (K is defined in Equation 7), N is the number of
active channels, and DCR is the Inductor DCR value.
Output-Voltage Offset Programming
RC
FB
⎛ I OUT
⎞
400
1
V OUT = V REF – V OFS – ⎜ ------------- ⋅ DCR ⋅ ⎛ ---------- ⋅ ---------------⎞ ⋅ K ⋅ RFB⎟
⎝ 3 R
⎠
⎝ N
⎠
SET
(EQ. 13)
VID
DAC
RGND
FIGURE 8. OUTPUT VOLTAGE AND LOAD-LINE
REGULATION WITH OFFSET ADJUSTMENT
The ISL6323 allows the designer to accurately adjust the
offset voltage by connecting a resistor, ROFS, from the OFS
pin to VCC or GND. When ROFS is connected between OFS
and VCC, the voltage across it is regulated to 1.6V. This
causes a proportional current (IOFS) to flow into the FB pin
and out of the OFS pin. If ROFS is connected to ground, the
voltage across it is regulated to 0.3V, and IOFS flows into the
OFS pin and out of the FB pin. The offset current flowing
through the resistor between VDIFF and FB will generate the
desired offset voltage which is equal to the product
(IOFS x RFB). These functions are shown in Figures 9
and 10.
Once the desired output offset voltage has been determined,
use Equations 14 and 15 to set ROFS:
Load-Line (Droop) Regulation
For Positive Offset (connect ROFS to GND):
By adding a well controlled output impedance, the output
voltage can effectively be level shifted in a direction which
works to achieve a cost-effective solution can help to reduce
the output-voltage spike that results from fast load-current
demand changes.
0.3 × R FB
R OFS = -------------------------V OFFSET
The magnitude of the spike is dictated by the ESR and ESL
of the output capacitors selected. By positioning the no-load
voltage level near the upper specification limit, a larger
negative spike can be sustained without crossing the lower
limit. By adding a well controlled output impedance, the
output voltage under load can effectively be level shifted
down so that a larger positive spike can be sustained without
crossing the upper specification limit.
As shown in Figure 8, with the FS resistor tied to ground, the
average current of all active channels, IAVG, flows from FB
through a load-line regulation resistor RFB. The resulting
voltage drop across RFB is proportional to the output current,
effectively creating an output voltage droop with a steadystate value defined as in Equation 12:
V DROOP = I AVG ⋅ R FB
(EQ. 12)
(EQ. 14)
For Negative Offset (connect ROFS to VCC):
1.6 × R FB
R OFS = -------------------------V OFFSET
(EQ. 15)
VDIFF
VOFS
+
RFB
VREF
+
E/A
-
FB
IOFS
+
-
VCC
-
ROFS
-
+
The regulated output voltage is reduced by the droop voltage
VDROOP. The output voltage as a function of load current is
shown in Equation 13.
OFS
ISL6323
-
1.6V
+
+
0.3V
GND
VCC
FIGURE 9. NEGATIVE OFFSET OUTPUT VOLTAGE
PROGRAMMING
19
FN9278.5
May 17, 2011
ISL6323
VOUT
RFB
VSEN
+
VOFS
-
RFB
IDVC = IC
IC
IDVC
+
VREF
CC
E/A
CDVC
-
FB
DVC
IOFS
COMP
FB
+
2x
-
+
VDAC+RGND
-
+
OFS
-
ISL6323
0.3V
GND
GND
1.6V
+
+
ROFS
RC
RDVC
VCC
FIGURE 10. POSITIVE OFFSET OUTPUT VOLTAGE
PROGRAMMING
Dynamic VID
The AMD processor does not step the output voltage
commands up or down to the target voltage, but instead
passes only the target voltage to the ISL6323 through either
the PVI or SVI interface. The ISL6323 manages the resulting
VID-on-the-Fly transition in a controlled manner, supervising
a safe output voltage transition without discontinuity or
disruption. The ISL6323 begins slewing the DAC at
3.25mV/µs until the DAC and target voltage are equal. Thus,
the total time required for a dynamic VID transition is
dependent only on the size of the DAC change.
To further improve dynamic VID performance, ISL6323 also
implements a proprietary DAC smoothing feature. The
external series RC components connected between DVC
and FB limit any stair-stepping of the output voltage during a
VID-on-the-Fly transition.
Compensating Dynamic VID Transitions
During a VID transition, the resulting change in voltage on
the FB pin and the COMP pin causes an AC current to flow
through the error amplifier compensation components from
the FB to the COMP pin. This current then flows through the
feedback resistor, RFB, and can cause the output voltage to
overshoot or undershoot at the end of the VID transition. In
order to ensure the smooth transition of the output voltage
during a VID change, a VID-on-the-fly compensation
network is required. This network is composed of a resistor
and capacitor in series, RDVC and CDVC, between the DVC
and the FB pin.
20
ERROR
AMPLIFIER
ISL6323 INTERNAL CIRCUIT
FIGURE 11. DYNAMIC VID COMPENSATION NETWORK
This VID-on-the-fly compensation network works by
sourcing AC current into the FB node to offset the effects of
the AC current flowing from the FB to the COMP pin during a
VID transition. To create this compensation current the
ISL6323 sets the voltage on the DVC pin to be 2x the voltage
on the REF pin. Since the error amplifier forces the voltage
on the FB pin and the REF pin to be equal, the resulting
voltage across the series RC between DVC and FB is equal
to the REF pin voltage. The RC compensation components,
RDVC and CDVC, can then be selected to create the desired
amount of compensation current.
The amount of compensation current required is dependant
on the modulator gain of the system, K1, and the error
amplifier RC components, RC and CC, that are in series
between the FB and COMP pins. Use Equations 16, 17, and
18 to calculate the RC component values, RDVC and CDVC,
for the VID-on-the-fly compensation network. For these
equations: VIN is the input voltage for the power train; VP-P
is the oscillator ramp amplitude (1.5V); and RC and CC are
the error amplifier RC components between the FB and
COMP pins.
V IN
K1 = ---------------VP – P
K1
A = ----------------K1 – 1
(EQ. 16)
R RCOMP = A × R C
(EQ. 17)
CC
C RCOMP = -------A
(EQ. 18)
Advanced Adaptive Zero Shoot-Through Deadtime
Control (Patent Pending)
The integrated drivers incorporate a unique adaptive deadtime
control technique to minimize deadtime, resulting in high
efficiency from the reduced freewheeling time of the lower
MOSFET body-diode conduction, and to prevent the upper and
lower MOSFETs from conducting simultaneously. This is
accomplished by ensuring either rising gate turns on its
MOSFET with minimum and sufficient delay after the other has
turned off.
FN9278.5
May 17, 2011
ISL6323
During turn-off of the lower MOSFET, the PHASE voltage is
monitored until it reaches a -0.3V/+0.8V (forward/reverse
inductor current). At this time the UGATE is released to rise. An
auto-zero comparator is used to correct the rDS(ON) drop in the
phase voltage preventing false detection of the -0.3V phase
level during rDS(ON) conduction period. In the case of zero
current, the UGATE is released after 35ns delay of the LGATE
dropping below 0.5V. When LGATE first begins to transition
low, this quick transition can disturb the PHASE node and
cause a false trip, so there is 20ns of blanking time once
LGATE falls until PHASE is monitored.
Once the PHASE is high, the advanced adaptive
shoot-through circuitry monitors the PHASE and UGATE
voltages during a PWM falling edge and the subsequent
UGATE turn-off. If either the UGATE falls to less than 1.75V
above the PHASE or the PHASE falls to less than +0.8V, the
LGATE is released to turn-on.
Initialization
Prior to initialization, proper conditions must exist on the EN,
VCC, PVCC1_2, PVCC_NB, ISEN3-, and ISEN4- pins. When
the conditions are met, the controller begins soft-start. Once
the output voltage is within the proper window of operation,
the controller asserts VDDPWRGD.
ISL6323 INTERNAL CIRCUIT
EXTERNAL CIRCUIT
VCC
PVCC1_2
PVCC_NB
+12V
POR
CIRCUIT
ENABLE
COMPARATOR
+
-
10.7kΩ
EN
1.00kΩ
VEN_THR
ISEN3SOFT-START
AND
FAULT LOGIC
CHANNEL
DETECT
ISEN4-
FIGURE 12. POWER SEQUENCING USING THRESHOLDSENSITIVE ENABLE (EN) FUNCTION
The bias voltage applied to VCC must reach the internal
power-on reset (POR) rising threshold. Once this threshold
is reached, the ISL6323 has enough bias to begin checking
the driver POR inputs, EN, and channel detect portions of
the initialization cycle. Hysteresis between the rising and
falling thresholds assure the ISL6323 will not advertently
turn off unless the bias voltage drops substantially (see
“Electrical Specifications” on page 9).
The bias voltage applied to the PVCC1_2 and PVCC_NB
pins power the internal MOSFET drivers of each output
channel. In order for the ISL6323 to begin operation, both
PVCC inputs must exceed their POR rising threshold to
guarantee proper operation of the internal drivers.
Hysteresis between the rising and falling thresholds assure
that once enabled, the ISL6323 will not inadvertently turn off
unless the PVCC bias voltage drops substantially (see
“Electrical Specifications” on page 9). Depending on the
number of active CORE channels determined by the Phase
Detect block, the external driver POR checking is supported
by the Enable Comparator.
Enable Comparator
The ISL6323 features a dual function enable input (EN) for
enabling the controller and power sequencing between the
controller and external drivers or another voltage rail. The
enable comparator holds the ISL6323 in shutdown until the
voltage at EN rises above 0.86V. The enable comparator has
about 110mV of hysteresis to prevent bounce. It is important
that the driver ICs reach their rising POR level before the
ISL6323 becomes enabled. The schematic in Figure 12
demonstrates sequencing the ISL6323 with the ISL66xx
family of Intersil MOSFET drivers, which require 12V bias.
When selecting the value of the resistor divider the driver
maximum rising POR threshold should be used for
calculating the proper resistor values. This will prevent
improper sequencing events from creating false trips during
soft-start.
If the controller is configured for 2-phase CORE operation,
then the resistor divider can be used for sequencing the
controller with another voltage rail. The resistor divider to EN
should be selected using a similar approach as the previous
driver discussion.
The EN pin is also used to force the ISL6323 into either PVI
or SVI mode. The mode is set upon the rising edge of the EN
signal. When the voltage on the EN pin rises above 0.86V,
the mode will be set depending upon the status of the
VID1/SEL pin.
Phase Detection
Power-On Reset
The ISL6323 requires VCC, PVCC1_2, and PVCC_NB
inputs to exceed their rising POR thresholds before the
ISL6323 has sufficient bias to guarantee proper operation.
21
The ISEN3- and ISEN4- pins are monitored prior to soft-start
to determine the number of active CORE channel phases.
If ISEN4- is tied to VCC, the controller will configure the
channel firing order and timing for 3-phase operation. If
ISEN3- and ISEN4- are tied to VCC, the controller will set
FN9278.5
May 17, 2011
ISL6323
the channel firing order and timing for 2-phase operation
(see “PWM Operation” on page 13 for details). If Channel 4
and/or Channel 3 are disabled, then the corresponding
PWMn and ISENn+ pins may be left unconnected.
.
VNB
400mV/DIV
Soft-Start Output Voltage Targets
Once the POR and Phase Detect blocks and enable
comparator are satisfied, the controller will begin the
soft-start sequence and will ramp the CORE and NB output
voltages up to the SVI interface designated target level if the
controller is set SVI mode. If set to PVI mode, the North
Bridge regulator is disabled and the core is soft started to the
level designated by the parallel VID code.
TDA
VCORE
400mV/DIV
TDB
EN
5V/DIV
VDDPWRGD
5V/DIV
SVI MODE
Prior to soft-starting both CORE and NB outputs, the
ISL6323 must check the state of the SVI interface inputs to
determine the correct target voltages for both outputs. When
the controller is enabled, the state of the VFIXEN, SVD and
SVC inputs are checked and the target output voltages set
for both CORE and NB outputs are set by the DAC (see
“Serial VID Interface (SVI)” on page 16). These targets will
only change if the EN signal is pulled low or after a POR
reset of VCC.
Soft-Start
The soft-start sequence is composed of three periods, as
shown in Figure 13. At the beginning of soft-start, the DAC
immediately obtains the output voltage targets for both
outputs by decoding the state of the SVI or PVI inputs. A
100µs fixed delay time, TDA, proceeds the output voltage
rise. After this delay period the ISL6323 will begin ramping
both CORE and NB output voltages to the programmed DAC
level at a fixed rate of 3.25mV/µs. The amount of time
required to ramp the output voltage to the final DAC voltage
is referred to as TDB, and can be calculated as shown in
Equation 19.
V DAC
TDB = -----------------------------–3
3.25 × 10
100µs/DIV
FIGURE 13. SOFT-START WAVEFORMS
Pre-Biased Soft-Start
The ISL6323 also has the ability to start up into a
pre-charged output, without causing any unnecessary
disturbance. The FB pin is monitored during soft-start, and
should it be higher than the equivalent internal ramping
reference voltage, the output drives hold both MOSFETs off.
Once the internal ramping reference exceeds the FB pin
potential, the output drives are enabled, allowing the output to
ramp from the pre-charged level to the final level dictated by
the DAC setting. Should the output be pre-charged to a level
exceeding the DAC setting, the output drives are enabled at
the end of the soft-start period, leading to an abrupt correction
in the output voltage down to the DAC-set level.
Both CORE and NB output support start up into a
pre-charged output.
OUTPUT PRECHARGED
ABOVE DAC LEVEL
(EQ. 19)
OUTPUT PRECHARGED
BELOW DAC LEVEL
After the DAC voltage reaches the final VID setting,
VDDPWRGD will be set to high.
VCORE
400mV/DIV
EN
5V/DIV
100µs/DIV
FIGURE 14. SOFT-START WAVEFORMS FOR ISL6323-BASED
MULTIPHASE CONVERTER
22
FN9278.5
May 17, 2011
ISL6323
Overvoltage Protection
-
142µA
OCL
+
100µA
REPEAT FOR EACH
CORE CHANNEL
-
OCP
INB
I1
+
-
100µA
+
IAVG
OCP
CORE ONLY
NB ONLY
SOFT-START, FAULT
AND CONTROL LOGIC
DUPLICATED FOR
NB AND CORE
1.8V
+
OVP
-
DAC + 250mV
+
-
VSEN
DAC - 300mV
UV
VDDPWRGD
ISL6323 INTERNAL CIRCUITRY
FIGURE 15. POWER-GOOD AND PROTECTION CIRCUITRY
Fault Monitoring and Protection
The ISL6323 actively monitors both CORE and NB output
voltages and currents to detect fault conditions. Fault
monitors trigger protective measures to prevent damage to
either load. One common power good indicator is provided
for linking to external system monitors. The schematic in
Figure 15 outlines the interaction between the fault monitors
and the power good signal.
Power-Good Signal
The power-good pin (VDDPWRGD) is an open-drain logic
output that signals whether or not the ISL6323 is regulating
both NB and CORE output voltages within the proper levels,
and whether any fault conditions exist. This pin should be
tied to a +5V source through a resistor.
During shutdown and soft-start, VDDPWRGD pulls low and
releases high after a successful soft-start and both output
voltages are operating between the undervoltage and
overvoltage limits. VDDPWRGD transitions low when an
undervoltage, overvoltage, or overcurrent condition is
detected on either output or when the controller is disabled
by a POR reset or EN. In the event of an overvoltage or
overcurrent condition, the controller latches off and
VDDPWRGD will not return high. Pending a POR reset of
the ISL6323 and successful soft-start, the VDDPWRGD will
return high.
23
At the inception of an overvoltage event, both on-board
lower gate pins are commanded low as are the active PWM
outputs to the external drivers, the VDDPWRGD signal is
driven low, and the ISL6323 latches off normal PWM action.
This turns on the all of the lower MOSFETs and pulls the
output voltage below a level that might cause damage to the
load. The lower MOSFETs remain driven ON until VDIFF
falls below 400mV. The ISL6323 will continue to protect the
load in this fashion as long as the overvoltage condition
recurs. Once an overvoltage condition ends the ISL6323
latches off, and must be reset by toggling POR, before a
soft-start can be re-initiated.
Pre-POR Overvoltage Protection
OV
+
The ISL6323 constantly monitors the sensed output voltage
on the VSEN pin to detect if an overvoltage event occurs.
When the output voltage rises above the OVP trip level and
exceeds the VDDPWRGD OV limit actions are taken by the
ISL6323 to protect the microprocessor load.
Prior to PVCC and VCC exceeding their POR levels, the
ISL6323 is designed to protect either load from any
overvoltage events that may occur. This is accomplished by
means of an internal 10kΩ resistor tied from PHASE to
LGATE, which turns on the lower MOSFET to control the
output voltage until the overvoltage event ceases or the input
power supply cuts off. For complete protection, the low side
MOSFET should have a gate threshold well below the
maximum voltage rating of the load/microprocessor.
In the event that during normal operation the PVCC or VCC
voltage falls back below the POR threshold, the pre-POR
overvoltage protection circuitry reactivates to protect from
any more pre-POR overvoltage events.
Undervoltage Detection
The undervoltage threshold is set at VDAC - 300mV typical.
When the output voltage (VSEN-RGND) is below the
undervoltage threshold, VDDPWRGD gets pulled low. No
other action is taken by the controller. VDDPWRGD will
return high if the output voltage rises above VDAC - 250mV
typical.
Open Sense Line Protection
In the case that either of the remote sense lines, VSEN or
GND, become open, the ISL6323 is designed to detect this
and shut down the controller. This event is detected by
monitoring small currents that are fed out the VSEN and
RGND pins. In the event of an open sense line fault, the
controller will continue to remain off until the fault goes away,
at which point the controller will re-initiate a soft-start
sequence.
Overcurrent Protection
The ISL6323 takes advantage of the proportionality between
the load current and the average current, IAVG, to detect an
overcurrent condition. See “Continuous Current Sampling”
FN9278.5
May 17, 2011
ISL6323
on page 14 and “Channel-Current Balance” on page 15 for
more detail on how the average current is measured. Once
the average current exceeds 100µA, a comparator triggers
the converter to begin overcurrent protection procedures.
The Core regulator and the North Bridge regulator have the
same type of overcurrent protection.
overcurrent shutdown will be initiated. This will result in a
continuous hiccup mode.
Note that the energy delivered during trip-retry cycling is
much less than during full-load operation, so there is no
thermal hazard.
The overcurrent trip threshold is dictated by the DCR of the
inductors, the number of active channels, the DC gain of the
inductor RC filter and the RSET resistor. The overcurrent trip
threshold is shown in Equation 20.
V IN – N ⋅ V OUT V OUT
N
1
3
I OCP = 100μA ⋅ ------------- ⋅ ---- ⋅ ⎛ ---------- ⋅ R SET⎞ – ---------------------------------------- ⋅ ---------------⎝
⎠
2 ⋅ L ⋅ fS
V IN
DCR K 400
(EQ. 20)
OUTPUT CURRENT, 50A/DIV
0A
Where:
R2
K = -------------------R1 + R2
OUTPUT VOLTAGE,
500mV/DIV
See “Continuous Current Sampling” on
page 14.
fS = Switching Frequency
0V
Equation 20 is valid for both the Core regulator and the
North Bridge regulator. This equation includes the DC load
current as well as the total ripple current contributed by all
the phases. For the North Bridge regulator, N is 1.
During soft-start, the overcurrent trip point is boosted by a
factor of 1.4. Instead of comparing the average measured
current to 100µA, the average current is compared to 140µA.
Immediately after soft-start is over, the comparison level
changes to 100µA. This is done to allow for start-up into an
active load while still supplying output capacitor in-rush
current.
CORE REGULATOR OVERCURRENT
At the beginning of overcurrent shutdown, the controller sets
all of the UGATE and LGATE signals low, puts PWM3 and
PWM4 (if active) in a high-impedance state, and forces
VDDPWRGD low. This turns off all of the upper and lower
MOSFETs. The system remains in this state for fixed period of
12ms. If the controller is still enabled at the end of this wait
period, it will attempt a soft-start, as shown in Figure 16. If the
fault remains, the trip-retry cycles will continue until either the
fault is cleared or for a total of seven attempts. If the fault is
not cleared on the final attempt, the controller disables
UGATE and LGATE signals for both Core and North Bridge
and latches off requiring a POR of VCC to reset the ISL6323.
It is important to note that during soft start, the overcurrent
trip point is increased by a factor of 1.4. If the fault draws
enough current to trip overcurrent during normal run mode, it
may not draw enough current during the soft-start ramp
period to trip overcurrent while the output is ramping up. If a
fault of this type is affecting the output, then the regulator will
complete soft-start and the trip-retry counter will be reset to
zero. Once the regulator has completed soft-start, the
overcurrent trip point will return to it’s nominal setting and an
24
3ms/DIV
FIGURE 16. OVERCURRENT BEHAVIOR IN HICCUP MODE
NORTH BRIDGE REGULATOR OVERCURRENT
The overcurrent shutdown sequence for the North Bridge
regulator is identical to the Core regulator with the exception
that it is a single phase regulator and will only disable the
MOSFET drivers for the North Bridge. Once 7 retry attempts
have been executed unsuccessfully, the controller will disable
UGATE and LGATE signals for both Core and North Bridge
and will latch off requiring a POR of VCC to reset the ISL6323.
Note that the energy delivered during trip-retry cycling is
much less than during full-load operation, so there is no
thermal hazard.
Individual Channel Overcurrent Limiting
The ISL6323 has the ability to limit the current in each
individual channel of the Core regulator without shutting
down the entire regulator. This is accomplished by
continuously comparing the sensed currents of each channel
with a constant 140µA OCL reference current. If a channel’s
individual sensed current exceeds this OCL limit, the UGATE
signal of that channel is immediately forced low, and the
LGATE signal is forced high. This turns off the upper
MOSFET(s), turns on the lower MOSFET(s), and stops the
rise of current in that channel, forcing the current in the
channel to decrease. That channel’s UGATE signal will not
be able to return high until the sensed channel current falls
back below the 140µA reference.
Exclusive Operation in Parallel Mode
The ISL6323 was designed such that the processor would
be the determining factor of whether the ISL6323 operated
in PVI mode or in SVI mode. If, however, the ISL6323 is to
be used in a system that will be used exclusively in parallel
mode and the North Bridge regulator will not be populated at
FN9278.5
May 17, 2011
ISL6323
all, there are some pin connections that must be made in
order for the ISL6323 to function properly. The ISEN_NB+
(pin 2) and ISEN_NB- (pin 47) pins as well as the RGND_NB
pin (pin 3) must be tied to ground. A small trace from the pin
to the ground pad under the part is all that is required. The
PVCC_NB pin (pin 42) should be tied to either +5V or to
+12V with a small decoupling capacitor to ground. All other
pins associated with the North Bridge regulator may be left
unconnected.
An additional term can be added to the lower-MOSFET loss
equation to account for additional loss accrued during the
dead time when inductor current is flowing through the
lower-MOSFET body diode. This term is dependent on the
diode forward voltage at IM, VD(ON), the switching
frequency, fS, and the length of dead times, td1 and td2, at
the beginning and the end of the lower-MOSFET conduction
interval respectively.
P
General Design Guide
This design guide is intended to provide a high-level
explanation of the steps necessary to create a multiphase
power converter. It is assumed that the reader is familiar with
many of the basic skills and techniques referenced in the
following. In addition to this guide, Intersil provides complete
reference designs that include schematics, bills of materials,
and example board layouts for all common microprocessor
applications.
Power Stages
The first step in designing a multiphase converter is to
determine the number of phases. This determination
depends heavily on the cost analysis which in turn depends
on system constraints that differ from one design to the next.
Principally, the designer will be concerned with whether
components can be mounted on both sides of the circuit
board, whether through-hole components are permitted, the
total board space available for power-supply circuitry, and
the maximum amount of load current. Generally speaking,
the most economical solutions are those in which each
phase handles between 25A and 30A. All surface-mount
designs will tend toward the lower end of this current range.
If through-hole MOSFETs and inductors can be used, higher
per-phase currents are possible. In cases where board
space is the limiting constraint, current can be pushed as
high as 40A per phase, but these designs require heat sinks
and forced air to cool the MOSFETs, inductors and heat
dissipating surfaces.
MOSFETS
The choice of MOSFETs depends on the current each
MOSFET will be required to conduct, the switching frequency,
the capability of the MOSFETs to dissipate heat, and the
availability and nature of heat sinking and air flow.
LOWER MOSFET POWER CALCULATION
The calculation for power loss in the lower MOSFET is
simple, since virtually all of the loss in the lower MOSFET is
due to current conducted through the channel resistance
(rDS(ON)). In Equation 21, IM is the maximum continuous
output current, IP-P is the peak-to-peak inductor current (see
Equation 2), and d is the duty cycle (VOUT/VIN).
2
I L ( P-P ) ⋅ ( 1 – d )
⎛ I M⎞ 2
P LOW, 1 = r DS ( ON ) ⋅ ⎜ -----⎟ ⋅ ( 1 – d ) + ------------------------------------------12
⎝ N⎠
25
LOW, 2
= V
D ( ON )
⋅f
S
⎛I
⎞
⎛I
⎞
⎟
M I P-P⎟ ⋅ t
M I----------⋅ ⎜ -----+ ⎜ -----+ ----------– P-P⎟ ⋅ t d2
2 ⎠
⎝N
2 ⎠ d1 ⎜⎝ N
(EQ. 22)
The total maximum power dissipated in each lower MOSFET
is approximated by the summation of PLOW,1 and PLOW,2.
UPPER MOSFET POWER CALCULATION
In addition to rDS(ON) losses, a large portion of the upper
MOSFET losses are due to currents conducted across the
input voltage (VIN) during switching. Since a substantially
higher portion of the upper-MOSFET losses are dependent
on switching frequency, the power calculation is more
complex. Upper MOSFET losses can be divided into
separate components involving the upper-MOSFET
switching times, the lower-MOSFET body-diode reverse
recovery charge, Qrr, and the upper MOSFET rDS(ON)
conduction loss.
When the upper MOSFET turns off, the lower MOSFET does
not conduct any portion of the inductor current until the
voltage at the phase node falls below ground. Once the
lower MOSFET begins conducting, the current in the upper
MOSFET falls to zero as the current in the lower MOSFET
ramps up to assume the full inductor current. In Equation 23,
the required time for this commutation is t1 and the
approximated associated power loss is PUP(1).
I M I P-P⎞ ⎛ t 1 ⎞
P UP( 1 ) ≈ V IN ⋅ ⎛ ----- ⋅ ⎜ ---- ⎟ ⋅ f
⎝ N- + --------2 ⎠ ⎝ 2⎠ S
(EQ. 23)
At turn-on, the upper MOSFET begins to conduct and this
transition occurs over a time t2. In Equation 24, the
approximate power loss is PUP(2).
⎛ I M I P-P⎞ ⎛ t 2 ⎞
P UP( 2 ) ≈ V IN ⋅ ⎜ ----- – ----------⎟ ⋅ ⎜ ---- ⎟ ⋅ f S
2 ⎠ ⎝ 2⎠
⎝N
(EQ. 24)
A third component involves the lower MOSFET
reverse-recovery charge, Qrr. Since the inductor current has
fully commutated to the upper MOSFET before the
lower-MOSFET body diode can recover all of Qrr, it is
conducted through the upper MOSFET across VIN. The
power dissipated as a result is PUP(3) as shown in
Equation 25.
P UP( 3 ) = V IN ⋅ Q rr ⋅ f S
(EQ. 25)
(EQ. 21)
FN9278.5
May 17, 2011
ISL6323
Finally, the resistive part of the upper MOSFET is given in
Equation 26 as PUP(4).
2
I P-P
⎛ I M⎞
P UP( 4 ) ≈ r DS ( ON ) ⋅ ⎜ -----⎟ ⋅ d + ---------12
⎝ N⎠
2
(EQ. 26)
The total power dissipated by the upper MOSFET at full load
can now be approximated as the summation of the results
from Equations 23, 24, 25 and 26. Since the power
equations depend on MOSFET parameters, choosing the
correct MOSFETs can be an iterative process involving
repetitive solutions to the loss equations for different
MOSFETs and different switching frequencies.
Internal Bootstrap Device
All three integrated drivers feature an internal bootstrap
Schottky diode. Simply adding an external capacitor across
the BOOT and PHASE pins completes the bootstrap circuit.
The bootstrap function is also designed to prevent the
bootstrap capacitor from overcharging due to the large
negative swing at the PHASE node. This reduces voltage
stress on the boot to phase pins.
The bootstrap capacitor must have a maximum voltage
rating above PVCC + 4V and its capacitance value can be
chosen from Equation 27:
Q GATE
C BOOT_CAP ≥ -------------------------------------ΔV BOOT_CAP
(EQ. 27)
Q G1 • PVCC
Q GATE = ------------------------------------ • N Q1
V GS1
where QG1 is the amount of gate charge per upper MOSFET
at VGS1 gate-source voltage and NQ1 is the number of
control MOSFETs. The ΔVBOOT_CAP term is defined as the
allowable droop in the rail of the upper gate drive.
1.6
Package Power Dissipation
When choosing MOSFETs it is important to consider the
amount of power being dissipated in the integrated drivers
located in the controller. Since there are a total of three
drivers in the controller package, the total power dissipated
by all three drivers must be less than the maximum
allowable power dissipation for the QFN package.
Calculating the power dissipation in the drivers for a desired
application is critical to ensure safe operation. Exceeding the
maximum allowable power dissipation level will push the IC
beyond the maximum recommended operating junction
temperature of +125°C. The maximum allowable IC power
dissipation for the 7x7 QFN package is approximately 3.5W
at room temperature. See “Layout Considerations” on
page 33 for thermal transfer improvement suggestions.
When designing the ISL6323 into an application, it is
recommended that the following calculations is used to
ensure safe operation at the desired frequency for the
selected MOSFETs. The total gate drive power losses,
PQg_TOT, due to the gate charge of MOSFETs and the
integrated driver’s internal circuitry and their corresponding
average driver current can be estimated with Equations 28
and 29, respectively.
P Qg_TOT = P Qg_Q1 + P Qg_Q2 + I Q ⋅ VCC
(EQ. 28)
3
P Qg_Q1 = --- ⋅ Q G1 ⋅ PVCC ⋅ f SW ⋅ N Q1 ⋅ N PHASE
2
P Qg_Q2 = Q G2 ⋅ PVCC ⋅ f SW ⋅ N Q2 ⋅ N PHASE
3
+ Q G2 ⋅ N Q2⎞ ⋅ N PHASE ⋅ f SW + I Q
I DR = ⎛ --- ⋅ Q G1 ⋅ N
⎝2
⎠
Q1
1.2
CBOOT_CAP (µF)
The ISL6323 provides the user flexibility in choosing the
gate drive voltage for efficiency optimization. The controller
ties the upper and lower drive rails together. Simply applying
a voltage from 5V up to 12V on PVCC sets both gate drive
rail voltages simultaneously.
(EQ. 29)
1.4
Where, PQg_Q1 is the total upper gate drive power loss and
PQg_Q2 is the total lower gate drive power loss; the gate
charge (QG1 and QG2) is defined at the particular gate to
source drive voltage PVCC in the corresponding MOSFET
data sheet; IQ is the driver total quiescent current with no load
at both drive outputs; NQ1 and NQ2 are the number of upper
and lower MOSFETs per phase, respectively; NPHASE is the
number of active phases. The IQ*VCC product is the
quiescent power of the controller without load on the drives.
1.0
0.8
0.6
QGATE = 100nC
0.4
50nC
0.2
Gate Drive Voltage Versatility
20nC
0.0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
ΔVBOOT_CAP (V)
FIGURE 17. BOOTSTRAP CAPACITANCE vs BOOT RIPPLE
VOLTAGE
26
FN9278.5
May 17, 2011
ISL6323
PVCC
BOOT
D
CGD
RHI1
G
UGATE
RLO1
RG1
CDS
RGI1
CGS
Q1
S
PHASE
FIGURE 18. TYPICAL UPPER-GATE DRIVE TURN-ON PATH
D
CASE 1
CGD
RLO2
G
LGATE
RG2
CDS
RGI2
CGS
Q2
S
FIGURE 19. TYPICAL LOWER-GATE DRIVE TURN-ON PATH
The total gate drive power losses are dissipated among the
resistive components along the transition path and in the
bootstrap diode. The portion of the total power dissipated in
the controller itself is the power dissipated in the upper drive
path resistance (PDR_UP) the lower drive path resistance
(PDR_UP) and in the boot strap diode (PBOOT). The rest of
the power will be dissipated by the external gate resistors
(RG1 and RG2) and the internal gate resistors (RGI1 and
RGI2) of the MOSFETs. Figures 18 and 19 show the typical
upper and lower gate drives turn-on transition path. The total
power dissipation in the controller itself, PDR, can be roughly
estimated as Equation 30:
P DR = P DR_UP + P DR_LOW + P BOOT + ( I Q ⋅ VCC )
I NB
I Core
MAX
⋅ DCR NB < -------------------------- ⋅ DCR Core
N
MAX
(EQ. 31)
In Case 1, the DC voltage across the North Bridge inductor
at full load is less than the DC voltage across a single phase
of the Core regulator while at full load. Here, the DC voltage
across the Core inductors must be scaled down to match the
DC voltage across the North Bridge inductor, which will be
impressed across the ISEN_NB pins without any gain. So,
the R2 resistor for the North Bridge inductor RC filter is left
unpopulated and K = 1.
1. Choose a capacitor value for the North Bridge RC filter. A
0.1µF capacitor is a recommended starting point.
2. Calculate the value for resistor R1 using Equation 32:
R1
L NB
= -------------------------------------DCR
NB
NB ⋅ C NB
(EQ. 32)
3. Calculate the value for the RSET resistor using
Equation 33: (Derived from Equation 20).
V IN – V NB V NB⎞
400 DCR NB ⋅ K ⎛
R SET = ---------- ⋅ ------------------------------ ⋅ ⎜ I OCP
+ ----------------------------- ⋅ -----------⎟
100μA
3
NB 2 ⋅ L NB ⋅ f S V IN ⎠
⎝
Where: K = 1
P Qg_Q1
P BOOT = --------------------3
(EQ. 33)
4. Using Equation 34 (also derived from Equation 20),
calculate the value of K for the Core regulator.
100μA
N
3
K = ---------- ⋅ R SET ⋅ ------------------------------ ⋅ ----------------------------------------------------------------------------------------------------------V IN – N ⋅ V CORE V CORE
DCR CORE
400
I OCP
+ --------------------------------------------- ⋅ -------------------V IN
2 ⋅ L CORE ⋅ f S
CORE
R HI1
R LO1
⎛
⎞ P Qg_Q1
P DR_UP = ⎜ -------------------------------------- + ----------------------------------------⎟ ⋅ --------------------R
+
R
R
+
R
3
⎝ HI1
EXT1
LO1
EXT1⎠
R HI2
R LO2
⎛
⎞ P Qg_Q2
P DR_LOW = ⎜ -------------------------------------- + ----------------------------------------⎟ ⋅ --------------------R
+
R
R
+
R
2
⎝ HI2
EXT2
LO2
EXT2⎠
R GI1
R EXT1 = R G1 + ------------N Q1
There are 3 separate cases to consider when calculating
these component values. If the system under design will
never utilize the North Bridge regulator and the ISL6323 will
always be in parallel mode, then follow the instructions for
Case 3 and only calculate values for Core regulator
components.
For all three cases, use the expected VID voltage that would
be used at TDC for Core and North Bridge for the VCORE
and VNB variables, respectively.
PVCC
RHI2
and Core regulators, it is important to set the RSET value
and the inductor RC filter gain, K, properly. See “Continuous
Current Sampling” on page 14 and “Channel-Current
Balance” on page 15 for more details on the application of
the RSET resistor and the RC filter gain.
(EQ. 34)
5. Choose a capacitor value for the Core RC filters. A 0.1µF
capacitor is a recommended starting point.
R GI2
R EXT2 = R G2 + ------------N Q2
(EQ. 30)
Inductor DCR Current Sensing Component
Selection and RSET Value Calculation
With the single RSET resistor setting the value of the
effective internal sense resistors for both the North Bridge
27
FN9278.5
May 17, 2011
ISL6323
6. Calculate the values for R1 and R2 for Core.
Equations 35 and 36 will allow for their computation.
R2
Core
K = ---------------------------------------------R1
+ R2
(EQ. 35)
R1
⋅ R2
L Core
Core
Core
------------------------- = ---------------------------------------------⋅ C Core
DCR Core
+ R2
R1
Core
Core
(EQ. 36)
Core
Core
CASE 2
I NB
I Core
MAX
⋅ DCR NB > -------------------------- ⋅ DCR Core
N
MAX
(EQ. 37)
In Case 2, the DC voltage across the North Bridge inductor
at full load is greater than the DC voltage across a single
phase of the Core regulator while at full load. Here, the DC
voltage across the North Bridge inductor must be scaled
down to match the DC voltage across the Core inductors,
which will be impressed across the ISEN pins without any
gain. So, the R2 resistor for the Core inductor RC filters is
left unpopulated and K = 1.
1. Choose a capacitor value for the Core RC filter. A 0.1µF
capacitor is a recommended starting point.
2. Calculate the value for resistor R1:
R1
L Core
= -----------------------------------------------DCR Core ⋅ C Core
Core
(EQ. 38)
I NB
V IN – N ⋅ V CORE V CORE⎞
400 DCR CORE ⋅ K ⎛
R SET = ---------- ⋅ --------------------------------------- ⋅ ⎜ I OCP
+ --------------------------------------------- ⋅ --------------------⎟
N ⋅ 100μA
2 ⋅ L CORE ⋅ f S
V IN ⎠
3
CORE
⎝
Where: K = 1
(EQ. 39)
(Derived from Equation 20).
4. Using Equation 40 (also derived from Equation 20),
calculate the value of K for the North bridge regulator.
100μA
1
3
K = ---------- ⋅ R SET ⋅ --------------------- ⋅ -------------------------------------------------------------------------V IN – V NB V NB
DCR NB
400
I OCP
+ ----------------------------- ⋅ ----------NB 2 ⋅ L NB ⋅ f S V IN
(EQ. 40)
5. Choose a capacitor value for the North Bridge RC filter. A
0.1µF capacitor is a recommended starting point.
6. Calculate the values for R1 and R2 for North Bridge.
Equations 41 and 42 will allow for their computation.
R2
NB
K = ------------------------------------R1
+ R2
(EQ. 41)
R1
⋅ R2
L NB
NB
NB
--------------------= ------------------------------------- ⋅ C NB
DCR NB
+ R2
R1
NB
NB
(EQ. 42)
NB
28
I Core
MAX
⋅ DCR NB = -------------------------- ⋅ DCR Core
N
MAX
(EQ. 43)
In Case 3, the DC voltage across the North Bridge inductor
at full load is equal to the DC voltage across a single phase
of the Core regulator while at full load. Here, the full scale
DC inductor voltages for both North Bridge and Core will be
impressed across the ISEN pins without any gain. So, the R2
resistors for the Core and North Bridge inductor RC filters
are left unpopulated and K = 1 for both regulators.
For this Case, it is recommended that the overcurrent trip
point for the North Bridge regulator be equal to the
overcurrent trip point for the Core regulator divided by the
number of core phases.
1. Choose a capacitor value for the North Bridge RC filter. A
0.1µF capacitor is a recommended starting point.
2. Calculate the value for the North Bridge resistor R1:
R1
L NB
= -------------------------------------DCR
NB
NB ⋅ C NB
(EQ. 44)
3. Choose a capacitor value for the Core RC filter. A 0.1µF
capacitor is a recommended starting point.
4. Calculate the value for the Core resistor R1:
R1
3. Calculate the value for the RSET resistor using Equation 39:
NB
CASE 3
Core
L Core
= -----------------------------------------------DCR Core ⋅ C Core
(EQ. 45)
5. Calculate the value for the RSET resistor using Equation 46:
V IN – N ⋅ V CORE V CORE⎞
400 DCR CORE ⋅ K ⎛
R SET = ---------- ⋅ --------------------------------------- ⋅ ⎜ I OCP
+ --------------------------------------------- ⋅ --------------------⎟
N ⋅ 100μA
2 ⋅ L CORE ⋅ f S
V IN ⎠
3
CORE
⎝
Where: K = 1
(EQ. 46)
6. Calculate the OCP trip point for the North Bridge
regulator using equation 47. If the OCP trip point is higher
than desired, then the component values must be
recalculated utilizing Case 1. If the OCP trip point is lower
than desired, then the component values must be
recalculated utilizing Case 2.
I OCP
V IN – V NB V NB
3
1
= 100μA ⋅ --------------------- ⋅ ⎛ ---------- ⋅ R SET⎞ + ----------------------------- ⋅ ----------⎝
⎠
400
2
⋅ L NB ⋅ f S V IN
DCR
NB
NB
(EQ. 47)
NOTE: The values of RSET must be greater than 20kΩ and
less than 80kΩ. For all of the 3 previous cases, if the
calculated value of RSET is less than 20kΩ, then either the
OCP trip point needs to be increased or the inductor must be
changed to an inductor with higher DCR. If the RSET resistor
is greater than 80kΩ, then a value of RSET that is less than
80kΩ must be chosen and a resistor divider across both
North Bridge and Core inductors must be set up with proper
gain. This gain will represent the variable “K” in all equations.
It is also very important that the RSET resistor be tied
between the RSET pin and the VCC pin of the ISL6323.
FN9278.5
May 17, 2011
ISL6323
Inductor DCR Current Sensing Component Fine
Tuning
I
VIN
L
n
4. Replace R1 and R2 with the new values and check to see
that the error is corrected. Repeat the procedure if
necessary.
UGATE(n)
L
MOSFET
LGATE(n)
DCR
VOUT
+
VL(s)
VC(s)
R1
COUT
ΔV2
ΔV1
-
+
INDUCTOR
-
DRIVER
VOUT
C
R2
ISL6323 INTERNAL CIRCUIT
ITRAN
In
ΔI
SAMPLE
FIGURE 21. TIME CONSTANT MISMATCH BEHAVIOR
-
VC(s)
RISEN
ISEN
TO ACTIVE
CORE CHANNELS
-
+
+
ISENn-
Loadline Regulation Resistor
ISENn+
The loadline regulation resistor, labeled RFB in Figure 8,
sets the desired loadline required for the application.
Equation 50 can be used to calculate RFB.
VCC
{
RSET
V DROOP
MAX
R FB = --------------------------------------------------------------------I OUT
400
MAX DCR
---------- ⋅ -------------------------- ⋅ --------------- ⋅ K
N
R SET
3
RSET
TO NORTH BRIDGE
CSET
FIGURE 20. DCR SENSING CONFIGURATION
Due to errors in the inductance and/or DCR it may be
necessary to adjust the value of R1 and R2 to match the time
constants correctly. The effects of time constant mismatch
can be seen in the form of droop overshoot or undershoot
during the initial load transient spike, as shown in Figure 21.
Follow the steps below to ensure the RC and inductor
L/DCR time constants are matched accurately.
1. If the regulator is not utilizing droop, modify the circuit by
placing the frequency set resistor between FS and
Ground for the duration of this procedure.
2. Capture a transient event with the oscilloscope set to
about L/DCR/2 (sec/div). For example, with L = 1µH and
DCR = 1mΩ, set the oscilloscope to 500µs/div.
3. Record ΔV1 and ΔV2 as shown in Figure 21. Select new
values, R1(NEW) and R2(NEW) for the time constant
resistors based on the original values, R1(OLD) and
R2(OLD) using Equations 48 and 49.
ΔV 1
(EQ. 48)
R 1 ( NEW ) = R 1 ( OLD ) ⋅ ---------ΔV 2
ΔV 1
R 2 ( NEW ) = R 2 ( OLD ) ⋅ ---------ΔV 2
(EQ. 50)
Where K is defined in Equation 7.
If no loadline regulation is required, FS resistor should be
tied between the FS pin and VCC. To choose the value for
RFB in this situation, please refer to “Compensation Without
Loadline Regulation” on page 30.
Compensation With Loadline Regulation
The load-line regulated converter behaves in a similar
manner to a peak current mode controller because the two
poles at the output filter L-C resonant frequency split with the
introduction of current information into the control loop. The
final location of these poles is determined by the system
function, the gain of the current signal, and the value of the
compensation components, RC and CC.
(EQ. 49)
29
FN9278.5
May 17, 2011
ISL6323
C2 (OPTIONAL)
Case 1:
RC
CC
1
-------------------------------- > f 0
2⋅π⋅ L⋅C
2 ⋅ π ⋅ f 0 ⋅ V pp ⋅ L ⋅ C
R C = R FB ⋅ -------------------------------------------------------0.66 ⋅ V
COMP
IN
0.66 ⋅ V IN
C C = ----------------------------------------------------2 ⋅ π ⋅ V P-P ⋅ R FB ⋅ f 0
FB
ISL6323
RFB
Case 2:
1
1
-------------------------------- ≤ f 0 < -----------------------------------2 ⋅ π ⋅ C ⋅ ESR
2⋅π⋅ L⋅C
V P-P ⋅ ( 2 ⋅ π ) 2 ⋅ f 02 ⋅ L ⋅ C
R C = R FB ⋅ -----------------------------------------------------------------0.66 ⋅ V
VSEN
(EQ. 51)
IN
0.66 ⋅ V IN
C C = -------------------------------------------------------------------------------------2
2
( 2 ⋅ π ) ⋅ f 0 ⋅ V P-P ⋅ R FB ⋅ L ⋅ C
FIGURE 22. COMPENSATION CONFIGURATION FOR
LOAD-LINE REGULATED ISL6323 CIRCUIT
Since the system poles and zero are affected by the values
of the components that are meant to compensate them, the
solution to the system equation becomes fairly complicated.
Fortunately, there is a simple approximation that comes very
close to an optimal solution. Treating the system as though it
were a voltage-mode regulator, by compensating the L-C
poles and the ESR zero of the voltage mode approximation,
yields a solution that is always stable with very close to ideal
transient performance.
Select a target bandwidth for the compensated system, f0.
The target bandwidth must be large enough to assure
adequate transient performance, but smaller than 1/3 of the
per-channel switching frequency. The values of the
compensation components depend on the relationships of f0
to the L-C pole frequency and the ESR zero frequency. For
each of the following three, there is a separate set of
equations for the compensation components.
In Equation 51, L is the per-channel filter inductance divided
by the number of active channels; C is the sum total of all
output capacitors; ESR is the equivalent series resistance of
the bulk output filter capacitance; and VP-P is the
peak-to-peak sawtooth signal amplitude as described in the
“Electrical Specifications” table on page 9.
Once selected, the compensation values in Equation 51
assure a stable converter with reasonable transient
performance. In most cases, transient performance can be
improved by making adjustments to RC. Slowly increase the
value of RC while observing the transient performance on an
oscilloscope until no further improvement is noted. Normally,
CC will not need adjustment. Keep the value of CC from
Equation 51 unless some performance issue is noted.
The optional capacitor C2, is sometimes needed to bypass
noise away from the PWM comparator (see Figure 22). Keep
a position available for C2, and be prepared to install a high
frequency capacitor of between 22pF and 150pF in case any
leading edge jitter problem is noted.
30
Case 3:
1
f 0 > ------------------------------------2 ⋅ π ⋅ C ⋅ ESR
2 ⋅ π ⋅ f 0 ⋅ V pp ⋅ L
R C = R FB ⋅ --------------------------------------------0.66 ⋅ V IN ⋅ ESR
0.66 ⋅ V IN ⋅ ESR ⋅ C
C C = ----------------------------------------------------------------2 ⋅ π ⋅ V P-P ⋅ R FB ⋅ f 0 ⋅ L
Compensation Without Loadline Regulation
The non load-line regulated converter is accurately modeled
as a voltage-mode regulator with two poles at the L-C
resonant frequency and a zero at the ESR frequency. A
type-III controller, as shown in Figure 23, provides the
necessary compensation.
C2
RC
CC
COMP
FB
C1
R1
ISL6323
RFB
VSEN
FIGURE 23. COMPENSATION CIRCUIT WITHOUT LOAD-LINE
REGULATION
The first step is to choose the desired bandwidth, f0, of the
compensated system. Choose a frequency high enough to
assure adequate transient performance but not higher than 1/3
of the switching frequency. The type-III compensator has an
extra high-frequency pole, fHF. This pole can be used for added
noise rejection or to assure adequate attenuation at the error
amplifier high-order pole and zero frequencies. A good general
rule is to choose fHF = 10f0, but it can be higher if desired.
Choosing fHF to be lower than 10f0 can cause problems with
too much phase shift below the system bandwidth as shown in
Equation 52.
FN9278.5
May 17, 2011
ISL6323
must provide the transient energy until the regulator can
respond. Because it has a low bandwidth compared to the
switching frequency, the output filter limits the system
transient response. The output capacitors must supply or
sink load current while the current in the output inductors
increases or decreases to meet the demand.
.
C ⋅ ESR
R 1 = R FB ⋅ -------------------------------------------L ⋅ C – C ⋅ ESR
L ⋅ C – C ⋅ ESR
C 1 = -------------------------------------------R FB
0.75 ⋅ V IN
C 2 = ---------------------------------------------------------------------------------------------------2
( 2 ⋅ π ) ⋅ f 0 ⋅ f HF ⋅ ( L ⋅ C ) ⋅ R FB ⋅ V P-P
(EQ. 52)
2
V P-P ⋅ ⎛ 2π⎞ ⋅ f 0 ⋅ f HF ⋅ L ⋅ C ⋅ R FB
⎝ ⎠
R C = ----------------------------------------------------------------------------------------0.75 ⋅ V ⋅ ( 2 ⋅ π ⋅ f HF ⋅ L ⋅ C – 1 )
IN
0.75 ⋅ V IN ⋅ ( 2 ⋅ π ⋅ f HF ⋅ L ⋅ C – 1 )
C C = ---------------------------------------------------------------------------------------------------( 2 ⋅ π ) 2 ⋅ f 0 ⋅ f HF ⋅ ( L ⋅ C ) ⋅ R FB ⋅ V P-P
In the solutions to the compensation equations, there is a
single degree of freedom. For the solutions presented in
Equation 53, RFB is selected arbitrarily. The remaining
compensation components are then selected according to
Equation 53.
In Equation 53, L is the per-channel filter inductance divided
by the number of active channels; C is the sum total of all
output capacitors; ESR is the equivalent-series resistance of
the bulk output-filter capacitance; and VP-P is the
peak-to-peak sawtooth signal amplitude as described in
“Electrical Specifications” on page 9.
1
-------------------------------- > f 0
2⋅π⋅ L⋅C
0.66 ⋅ V IN
C C = ----------------------------------------------------2 ⋅ π ⋅ V P-P ⋅ R FB ⋅ f 0
1
1
-------------------------------- ≤ f 0 < -----------------------------------2 ⋅ π ⋅ C ⋅ ESR
2⋅π⋅ L⋅C
V P-P ⋅ ( 2 ⋅ π ) 2 ⋅ f 02 ⋅ L ⋅ C
R C = R FB ⋅ -----------------------------------------------------------------0.66 ⋅ V IN
(EQ. 53)
0.66 ⋅ V IN
C C = -------------------------------------------------------------------------------------( 2 ⋅ π ) 2 ⋅ f 02 ⋅ V P-P ⋅ R FB ⋅ L ⋅ C
Case 3:
1
f 0 > ------------------------------------2 ⋅ π ⋅ C ⋅ ESR
2 ⋅ π ⋅ f 0 ⋅ V P-P ⋅ L
R C = R FB ⋅ ---------------------------------------------0.66 ⋅ V IN ⋅ ESR
0.66 ⋅ V IN ⋅ ESR ⋅ C
C C = ----------------------------------------------------------------2 ⋅ π ⋅ V P-P ⋅ R FB ⋅ f 0 ⋅ L
The output inductors and the output capacitor bank together
to form a low-pass filter responsible for smoothing the
pulsating voltage at the phase nodes. The output filter also
31
(EQ. 54)
The filter capacitor must have sufficiently low ESL and ESR
so that ΔV < ΔVMAX.
2 ⋅ π ⋅ f 0 ⋅ V P-P ⋅ L ⋅ C
R C = R FB ⋅ ---------------------------------------------------------0.66 ⋅ V IN
Case 2:
At the beginning of the load transient, the output capacitors
supply all of the transient current. The output voltage will
initially deviate by an amount approximated by the voltage
drop across the ESL. As the load current increases, the
voltage drop across the ESR increases linearly until the load
current reaches its final value. The capacitors selected must
have sufficiently low ESL and ESR so that the total output
voltage deviation is less than the allowable maximum.
Neglecting the contribution of inductor current and regulator
response, the output voltage initially deviates by an amount
as shown in Equation 54:
di
ΔV ≈ ESL ⋅ ----- + ESR ⋅ ΔI
dt
Output Filter Design
Case 1:
In high-speed converters, the output capacitor bank is usually
the most costly (and often the largest) part of the circuit.
Output filter design begins with minimizing the cost of this part
of the circuit. The critical load parameters in choosing the
output capacitors are the maximum size of the load step, ΔI,
the load-current slew rate, di/dt, and the maximum allowable
output-voltage deviation under transient loading, ΔVMAX.
Capacitors are characterized according to their capacitance,
ESR, and ESL (equivalent series inductance).
Most capacitor solutions rely on a mixture of high frequency
capacitors with relatively low capacitance in combination
with bulk capacitors having high capacitance but limited
high-frequency performance. Minimizing the ESL of the
high-frequency capacitors allows them to support the output
voltage as the current increases. Minimizing the ESR of the
bulk capacitors allows them to supply the increased current
with less output voltage deviation.
The ESR of the bulk capacitors also creates the majority of
the output-voltage ripple. As the bulk capacitors sink and
source the inductor AC ripple current (see “Interleaving” on
page 12 and Equation 3), a voltage develops across the bulk
capacitor ESR equal to IC(P-P ) (ESR). Thus, once the output
capacitors are selected, the maximum allowable ripple
voltage, VP-P(MAX), determines the lower limit on the
inductance.
⎛V – N ⋅ V
⎞
OUT⎠ ⋅ V OUT
⎝ IN
L ≥ ESR ⋅ -------------------------------------------------------------------f S ⋅ V IN ⋅ V P-P(MAX)
(EQ. 55)
Since the capacitors are supplying a decreasing portion of
the load current while the regulator recovers from the
FN9278.5
May 17, 2011
ISL6323
Equation 56 gives the upper limit on L for the cases when
the trailing edge of the current transient causes a greater
output-voltage deviation than the leading edge. Equation 57
addresses the leading edge. Normally, the trailing edge
dictates the selection of L because duty cycles are usually
less than 50%. Nevertheless, both inequalities should be
evaluated, and L should be selected based on the lower of
the two results. In each equation, L is the per-channel
inductance, C is the total output capacitance, and N is the
number of active channels.
2 ⋅ N ⋅ C ⋅ VO
L ≤ --------------------------------- ⋅ ΔV MAX – ( ΔI ⋅ ESR )
( ΔI ) 2
(EQ. 56)
1.25 ⋅ N ⋅ C- ⋅ ΔV
⎛
⎞
L ≤ ---------------------------MAX – ( ΔI ⋅ ESR ) ⋅ ⎝ V IN – V O⎠
( ΔI ) 2
(EQ. 57)
Switching Frequency
Switching frequency is determined by the selection of the
frequency-setting resistor, RT. Figure 24 and Equation 58
are provided to assist in selecting the correct value for RT.
[10.61 – ( 1.035 ⋅ log ( f S ) ) ]
(EQ. 58)
RT (kΩ)
1k
0.3
IL(P-P) = 0
IL(P-P) = 0.25 IO
IL(P-P) = 0.5 IO
IL(P-P) = 0.75 IO
0.2
0.1
0
0.2
0.4
0.6
0.8
1.0
DUTY CYCLE (VO/VIN)
FIGURE 25. NORMALIZED INPUT-CAPACITOR RMS CURRENT
vs DUTY CYCLE FOR 4-PHASE CONVERTER
For a 4-phase design, use Figure 25 to determine the inputcapacitor RMS current requirement set by the duty cycle,
maximum sustained output current (IO), and the ratio of the
peak-to-peak inductor current (IL(P-P)) to IO. Select a bulk
capacitor with a ripple current rating which will minimize the
total number of input capacitors required to support the RMS
current calculated.
The voltage rating of the capacitors should also be at least
1.25x greater than the maximum input voltage. Figures 26
and 27 provide the same input RMS current information for
3-phase and 2-phase designs respectively. Use the same
approach for selecting the bulk capacitor type and number.
Low capacitance, high-frequency ceramic capacitors are
needed in addition to the input bulk capacitors to suppress
leading and falling edge voltage spikes. The spikes result from
the high current slew rate produced by the upper MOSFET
turn on and off. Select low ESL ceramic capacitors and place
one as close as possible to each upper MOSFET drain to
minimize board parasitics and maximize suppression.
100
10
60k
The input capacitors are responsible for sourcing the AC
component of the input current flowing into the upper
MOSFETs. Their RMS current capacity must be sufficient to
handle the AC component of the current drawn by the upper
MOSFETs which is related to duty cycle and the number of
active phases.
0
There are a number of variables to consider when choosing
the switching frequency, as there are considerable effects on
the upper MOSFET loss calculation. These effects are
outlined in “MOSFETs” on page 25, and they establish the
upper limit for the switching frequency. The lower limit is
established by the requirement for fast transient response
and small output-voltage ripple as outlined in “Output Filter
Design” on page 31. Choose the lowest switching frequency
that allows the regulator to meet the transient-response
requirements.
R T = 10
Input Capacitor Selection
INPUT-CAPACITOR CURRENT (IRMS/IO)
transient, the capacitor voltage becomes slightly depleted.
The output inductors must be capable of assuming the entire
load current before the output voltage decreases more than
ΔVMAX. This places an upper limit on inductance.
100k
1M
2M
SWITCHING FREQUENCY (Hz)
FIGURE 24. RT vs SWITCHING FREQUENCY
32
FN9278.5
May 17, 2011
ISL6323
INPUT-CAPACITOR CURRENT (IRMS/IO)
0.3
IL(P-P) = 0
IL(P-P) = 0.5 IO
IL(P-P) = 0.25 IO
IL(P-P)= 0.75 IO
most critical because they switch large amounts of energy. Next
are small signal components that connect to sensitive nodes or
supply critical bypassing current and signal coupling.
The power components should be placed first, which include
the MOSFETs, input and output capacitors, and the inductors. It
is important to have a symmetrical layout for each power train,
preferably with the controller located equidistant from each.
Symmetrical layout allows heat to be dissipated equally
across all power trains. Equidistant placement of the controller
to the CORE and NB power trains it controls through the
integrated drivers helps keep the gate drive traces equally
short, resulting in equal trace impedances and similar drive
capability of all sets of MOSFETs.
0.2
0.1
0
0
0.2
0.4
0.6
0.8
1.0
DUTY CYCLE (VIN/VO)
FIGURE 26. NORMALIZED INPUT-CAPACITOR RMS
CURRENT FOR 3-PHASE CONVERTER
INPUT-CAPACITOR CURRENT (IRMS/IO)
0.3
Locate the output inductors and output capacitors between the
MOSFETs and the load. The high-frequency output decoupling
capacitors (ceramic) should be placed as close as practicable
to the decoupling target, making use of the shortest connection
paths to any internal planes, such as vias to GND next or on the
capacitor solder pad.
0.2
0.1
IL(P-P) = 0
IL(P-P) = 0.5 IO
IL(P-P) = 0.75 IO
0
0
0.2
When placing the MOSFETs try to keep the source of the upper
FETs and the drain of the lower FETs as close as thermally
possible. Input high-frequency capacitors, CHF, should be
placed close to the drain of the upper FETs and the source of
the lower FETs. Input bulk capacitors, CBULK, case size
typically limits following the same rule as the high-frequency
input capacitors. Place the input bulk capacitors as close to the
drain of the upper FETs as possible and minimize the distance
to the source of the lower FETs.
0.4
0.6
0.8
1.0
DUTY CYCLE (VIN/VO)
FIGURE 27. NORMALIZED INPUT-CAPACITOR RMS
CURRENT FOR 2-PHASE CONVERTER
Layout Considerations
MOSFETs switch very fast and efficiently. The speed with which
the current transitions from one device to another causes
voltage spikes across the interconnecting impedances and
parasitic circuit elements. These voltage spikes can degrade
efficiency, radiate noise into the circuit and lead to device
overvoltage stress. Careful component selection, layout, and
placement minimizes these voltage spikes. Consider, as an
example, the turnoff transition of the upper PWM MOSFET.
Prior to turnoff, the upper MOSFET was carrying channel
current. During the turn-off, current stops flowing in the upper
MOSFET and is picked up by the lower MOSFET. Any
inductance in the switched current path generates a large
voltage spike during the switching interval. Careful component
selection, tight layout of the critical components, and short, wide
circuit traces minimize the magnitude of voltage spikes.
The critical small components include the bypass capacitors
(CFILTER) for VCC and PVCC, and many of the components
surrounding the controller including the feedback network and
current sense components. Locate the VCC/PVCC bypass
capacitors as close to the ISL6323 as possible. It is especially
important to locate the components associated with the
feedback circuit close to their respective controller pins, since
they belong to a high-impedance circuit loop, sensitive to EMI
pick-up.
A multi-layer printed circuit board is recommended. Figure 27
shows the connections of the critical components for the
converter. Note that capacitors CIN and COUT could each
represent numerous physical capacitors. Dedicate one solid
layer, usually the one underneath the component side of the
board, for a ground plane and make all critical component
ground connections with vias to this layer. Dedicate another
solid layer as a power plane and break this plane into smaller
islands of common voltage levels. Keep the metal runs from the
PHASE terminal to output inductors short. The power plane
should support the input power and output power nodes. Use
copper filled polygons on the top and bottom circuit layers for
the phase nodes. Use the remaining printed circuit layers for
small signal wiring.
There are two sets of critical components in a DC/DC converter
using a ISL6323 controller. The power components are the
33
FN9278.5
May 17, 2011
ISL6323
RFB
C2
+12V
+12V
CC
RC
FB
VSEN
COMP
CIN
R3_2
CBOOT
C3
BOOT1
ISEN3+
ISEN3-
CBOOT
CIN
BOOT1
R3_1
UGATE1
UGATE1
PWM3
PHASE1
PHASE1
RAPA
R1_1
CAPA
C1
LGATE1
LGATE1
APA
PGND
ISEN1ISEN1+
DVC
ISL6614
+12V
V_CORE
+5V
PVCC1_2
CFILTER
+12V
CIN
CFILTER
VCC
ROFS
CFILTER
CBOOT
BOOT2
CBULK
CHF
UGATE2
UGATE2
+12V
VCC
PVCC
BOOT2
CIN
CBOOT
OFS
GND
PHASE2
FS
CPU
LOAD
PHASE2
RFS
C2
C4
R2_2
R4_2
R2_1
RSET
PWM2
R4_1
LGATE2
LGATE2
RSET
VFIXEN
SEL
SVD
ISEN2ISEN2+
SVC
VID4
VID5
PWROK
NC
NC
PWM1
R1_2
RGND
VDDPWRGD
ISEN4+
GND
ISEN4-
PWM4
+12V
ISL6323
REN1
OFF
+12V
KEY
HEAVY TRACE ON CIRCUIT PLANE LAYER
PVCC_NB
CIN
CFILTER
EN
ISLAND ON POWER PLANE LAYER
ISLAND ON CIRCUIT PLANE LAYER
CBOOT_NB
ON
BOOT_NB
REN2
VIA CONNECTION TO GROUND PLANE
UGATE_NB
V_NB
PHASE_NB
R1_NB
LGATE_NB
ISEN_NBCOMP_NB
FB_NB
ISEN_NB+
RGND_NB
C2_NB
RC_NB
CC_NB
C1_NB
CBULK
CHF
R2_NB
RED COMPONENTS:
LOCATE CLOSE TO IC TO
MINIMIZE CONNECTION PATH
NB
LOAD
BLUE COMPONENTS:
LOCATE NEAR LOAD
(MINIMIZE CONNECTION PATH)
GREEN COMPONENTS:
LOCATE CLOSE TO SWITCHING TRANSISTORS
(MINIMIZE CONNECTION PATH)
RFB_NB
FIGURE 28. PRINTED CIRCUIT BOARD POWER PLANES AND ISLANDS
34
FN9278.5
May 17, 2011
ISL6323
Routing UGATE, LGATE, and PHASE Traces
Great attention should be paid to routing the UGATE, LGATE,
and PHASE traces since they drive the power train MOSFETs
using short, high current pulses. It is important to size them as
large and as short as possible to reduce their overall
impedance and inductance. They should be sized to carry at
least one ampere of current (0.02” to 0.05”). Going between
layers with vias should also be avoided, but if so, use two vias
for interconnection when possible.
Extra care should be given to the LGATE traces in particular
since keeping their impedance and inductance low helps to
significantly reduce the possibility of shoot-through. It is also
important to route each channels UGATE and PHASE traces
in as close proximity as possible to reduce their inductances.
Current Sense Component Placement and Trace
Routing
One of the most critical aspects of the ISL6323 regulator
layout is the placement of the inductor DCR current sense
components and traces. The R-C current sense components
must be placed as close to their respective ISEN+ and
ISEN- pins on the ISL6323 as possible.
The sense traces that connect the R-C sense components to
each side of the output inductors should be routed on the
bottom of the board, away from the noisy switching
components located on the top of the board. These traces
should be routed side by side, and they should be very thin
traces. It’s important to route these traces as far away from
any other noisy traces or planes as possible. These traces
should pick up as little noise as possible.
Thermal Management
For maximum thermal performance in high current, high
switching frequency applications, connecting the thermal GND
pad of the ISL6323 to the ground plane with multiple vias is
recommended. This heat spreading allows the part to achieve
its full thermal potential. It is also recommended that the
controller be placed in a direct path of airflow if possible to help
thermally manage the part.
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com
35
FN9278.5
May 17, 2011
ISL6323
Package Outline Drawing
L48.7x7
48 LEAD QUAD FLAT NO-LEAD PLASTIC PACKAGE
Rev 4, 10/06
4X 5.5
7.00
A
44X 0.50
B
37
6
PIN 1
INDEX AREA
6
PIN #1 INDEX AREA
48
1
7.00
36
4. 30 ± 0 . 15
12
25
(4X)
0.15
13
24
0.10 M C A B
48X 0 . 40± 0 . 1
TOP VIEW
4 0.23 +0.07 / -0.05
BOTTOM VIEW
SEE DETAIL "X"
( 6 . 80 TYP )
(
4 . 30 )
C
0.10 C
BASE PLANE
0 . 90 ± 0 . 1
SEATING PLANE
0.08 C
SIDE VIEW
( 44X 0 . 5 )
C
0 . 2 REF
5
( 48X 0 . 23 )
( 48X 0 . 60 )
0 . 00 MIN.
0 . 05 MAX.
TYPICAL RECOMMENDED LAND PATTERN
DETAIL "X"
NOTES:
1. Dimensions are in millimeters.
Dimensions in ( ) for Reference Only.
2. Dimensioning and tolerancing conform to AMSE Y14.5m-1994.
3. Unless otherwise specified, tolerance : Decimal ± 0.05
4. Dimension b applies to the metallized terminal and is measured
between 0.15mm and 0.30mm from the terminal tip.
5. Tiebar shown (if present) is a non-functional feature.
6. The configuration of the pin #1 identifier is optional, but must be
located within the zone indicated. The pin #1 identifier may be
either a mold or mark feature.
36
FN9278.5
May 17, 2011
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