DATASHEET

ISL6263
®
Data Sheet
• Input voltage range: +5.0V to +25.0V
• Programmable PWM frequency: 200kHz to 500kHz
• Pre-biased output start-up capability
• 5-bit voltage identification input (VID)
- 1.28750 to 0.41200V
- 25.75mV steps
- Sequential or non-sequential VID change on-the-fly
• Selectable diode emulation mode
- Render Suspend mode only
- Render Performance and Render Suspend mode
• Selectable audio filter in render suspend mode
• Integrated MOSFET drivers and bootstrap diode
• Choice of current sensing schemes
- Lossless inductor DCR current sensing
- Precision resistive current sensing
• Overvoltage, undervoltage, and overcurrent protection
• Pb-free plus anneal available (RoHS compliant)
Pinout
VR_ON
I2UA
VID4
VID3
VID2
ISL6263 (32 LD 5x5 QFN)
TOP VIEW
AF_EN
32
31
30
29
28
27
26
25
SOFT
2
23
VID0
OCSET
3
22
PVCC
VW
4
GND PAD
21
LGATE
COMP
5
(BOTTOM)
20
PGND
FB
6
19
PHASE
VDIFF
7
18
UGATE
VSEN
8
17
BOOT
RTN
9
1
10
11
12
13
14
15
16
VDD
VID1
VSS
24
VIN
1
VSUM
RBIAS
VO
The Render core voltage can be dynamically programmed
from 0.41200V to 1.28750V by the five VID input pins
without requiring sequential stepping of the VID states. The
ISL6263 uses the same capacitor for the soft-start slew-rate
and for the dynamic VID slew-rate by internally connecting
the SOFT pin to the appropriate current source. Processor
socket Kelvin sensing is accomplished with an integrated
unity-gain true differential amplifier.
• Applications up to 25A
DFB
To maximize light load efficiency, the ISL6263 automatically
transitions between continuous-conduction-mode (CCM)
and discontinuous-conduction-mode (DCM.) During DCM
the low-side MOSFET enters diode-emulation-mode (DEM.)
DEM is enabled whenever a Render Suspend state has
been set on the VID inputs. Optionally, DEM can be enabled
for all VID states by setting the FDE pin high. The ISL6263
has an audio filter that can be enabled in any Render
Suspend state by pulling the AF_EN pin high. The audio
filter prevents the PWM switching frequency from entering
the audible spectrum due to extremely light load while in
DEM.
• Precision single-phase core voltage regulator
- 0.5% system accuracy 0°C to +100°C
- Differential remote GPU die voltage sensing
- Differential droop voltage sensing
PGOOD
Intersil’s R3 Technology™ combines the best features of
both fixed-frequency PWM and hysteretic PWM, delivering
excellent light-load efficiency and superior load transient
response by commanding variable switching frequency
during the transitory event.
Features
DROOP
The ISL6263 IC is a Single-Phase Synchronous-Buck PWM
voltage regulator featuring Intersil’s Robust Ripple Regulator
(R3) Technology™. The ISL6263 is an implementation of the
Intel® Mobile Voltage Positioning (IMVP) protocol for GPU
Render Engine core power. Integrated MOSFET drivers,
bootstrap diode, and droop amplifier result in lower
component cost and smaller implementation area.
FN9213.2
FDE
5-Bit VID Single-Phase Voltage Regulator
for IMVP-6+ Santa Rosa GPU Core
June 10, 2010
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2006, 2010. All Rights Reserved. R3 Technology™ is a trademark of Intersil Americas Inc.
All other trademarks mentioned are the property of their respective owners.
ISL6263
Ordering Information
PART NUMBER
(Notes 2, 3)
PART
MARKING
TEMP RANGE
(°C)
PACKAGE
(Pb-Free)
PKG.
DWG. #
ISL6263CRZ
ISL 6263CRZ
-10 to 100
32 Ld 5x5 QFN
L32.5x5
ISL6263CRZ-T
(Note 1)
ISL 6263CRZ
-10 to 100
32 Ld 5x5 QFN Tape & Reel
L32.5x5
NOTES:
1. Please refer to TB347 for details on reel specifications.
2. 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 STD020.
3. For Moisture Sensitivity Level (MSL), please see device information page for ISL6263. For more information on MSL please see techbrief TB363.
2
FN9213.2
June 10, 2010
Block Diagram
I2UA
VDD
VREF
1:1
3
×2
−
SCP
+
SHORT
CIRCUIT
AUDIBLE
FREQUENCY
FILTER
OVER
CURRENT
UNDER
VOLTAGE
FAULT
LATCH
VO
+
Σ
+
+
−
VSEN
VID0
VW
gmVin
↓
IDVID
+
−
↓
VID4
VID DAC
↔
VID3
AF_EN
↓ ↓
VID1
ISS
+
E/A
−
FN9213.2
June 10, 2010
SOFT
FB
LGATE
FDE
+
−
VDIFF
VID2
DRIVER
PGND
↓
RTN
PVCC
COMP
VIN
FIGURE 1. SIMPLIFIED FUNCTIONAL BLOCK DIAGRAM OF THE ISL6263
PWM
R3
VW
MODULATOR
gmVsoft
VCOMP
ISL6263
+
−
SHOOT THROUGH
PROTECTION
SEVERE
OVERVOLTAGE
SOFT
CROWBAR
CONTROL
OVER
VOLTAGE
DROOP
UGATE
PHASE
Δ V W 33%
+
−
DRIVER
DIODE
EMULATION
PGOOD
−
OCP
+
OCSET
DFB
PWM
CONTROL
POR
RBIAS
VSUM
BOOT
↓ ↓
VSS
PGOOD
↓
VREF
1.545V
+
−
VR_ON
ISL6263
Simplified Application Circuit for DCR Current Sensing
RVDD
V5V
CVDD
CPVCC
VDD
PVCC
RRBIAS
RBIAS
VIN
VIN
CSOFT
QHS
SOFT
CIN
UGATE
RI2UA
I2UA
BOOT
LOUT
CBOOT
PGOOD
VCCGFX
PHASE
VID<0:4>
AF_EN
LGATE
FDE
VCC_SNS
VSEN
VSS_SNS
RTN
COUT
QLS
VR_ON
PGND
RS
RNTC
VW
VSUM
ISL6263
RFSET
CFSET
RNTCP
CN
RNTCS
VO
CCOMP1
ROCSET
COMP
RCOMP
RDRP1
OCSET
CCOMP2
DFB
FB
VDIFF
RDIFF2
RDRP2
CDIFF
CDRP
DROOP
VSS
RGND
RDIFF1
0
FIGURE 2. ISL6263 GPU RENDER-CORE VOLTAGE REGULATOR SOLUTION WITH DCR CURRENT SENSING
4
FN9213.2
June 10, 2010
ISL6263
Simplified Application Circuit for Resistive Current Sensing
RVDD
V5V
CPVCC
CVDD
VDD
PVCC
RRBIAS
RBIAS
VIN
VIN
CSOFT
QHS
SOFT
CIN
UGATE
RI2UA
I2UA
BOOT
LOUT
CBOOT
RSNS
VCCGFX
PHASE
PGOOD
VID<0:4>
LGATE
AF_EN
FDE
VCC_SNS
VSEN
VSS_SNS
RTN
COUT
QLS
VR_ON
PGND
RS
VW
VSUM
ISL6263
RFSET
CFSET
CN
VO
CCOMP1
ROCSET
COMP
RCOMP
RDRP1
OCSET
CCOMP2
DFB
FB
VDIFF
RDIFF2
RDRP2
CDIFF
CDRP
DROOP
VSS
RDIFF1
RGND
0
FIGURE 3. ISL6263 GPU RENDER-CORE VOLTAGE REGULATOR SOLUTION WITH RESISTIVE CURRENT SENSING
5
FN9213.2
June 10, 2010
ISL6263
Absolute Voltage Ratings
Thermal Information
VIN to VSS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +28V
VDD to VSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +7.0V
PVCC to PGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +7.0V
VSS to PGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +0.3V
PHASE to VSS. . . . . . . . . . . . . . . . . . . . . . . . . . (DC) -0.3V to +28V
(<100ns Pulse Width, 10µJ) -5.0V
BOOT to PHASE . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +7.0V
BOOT to VSS or PGND . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +33V
UGATE. . . . . . . . . . . . . . . . . . . (DC) -0.3V to PHASE, BOOT +0.3V
(<200ns Pulse Width, 20µJ) -4.0V
LGATE . . . . . . . . . . . . . . . . . . . . (DC) -0.3V to PGND, PVCC +0.3V
(<100ns Pulse Width, 4µJ) -2.0V
ALL Other Pins. . . . . . . . . . . . . . . . . . . . . -0.3V to VSS, VDD +0.3V
Thermal Resistance (Typical, Notes 4, 5) θJA (°C/W) θJC (°C/W)
QFN Package. . . . . . . . . . . . . . . . . . . .
35
6
Junction Temperature Range. . . . . . . . . . . . . . . . . .-55°C to +150°C
Operating Temperature Range . . . . . . . . . . . . . . . .-10°C to +100°C
Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . .-65°C to +150°C
Pb-Free Reflow Profile. . . . . . . . . . . . . . . . . . . . . . . . .see link below
http://www.intersil.com/pbfree/Pb-FreeReflow.asp
Recommended Operating Conditions
Ambient Temperature Range. . . . . . . . . . . . . . . . . . -10°C to 100°C
VIN to VSS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +5V to +25V
VDD to VSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +5V ±5%
PVCC to PGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +5V ±5%
FDE to VSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to +3.3V
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:
4. 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.
5. For θJC, the “case temp” location is the center of the exposed metal pad on the package underside.
Electrical Specifications
These specifications apply for TA = -10°C to +100°C, unless otherwise stated. All typical specifications
TA = +25°C, VDD = 5V, PVCC = 5V. Boldface limits apply over the operating temperature range,
-10°C to +100°C.
PARAMETER
SYMBOL
MIN
(Note 6)
TYP
MAX
(Note 6)
UNITS
VR_ON = 3.3V
-
1.0
-
MΩ
VR_ON = 0V, VIN = 25V
-
-
1.0
µA
VR_ON = 3.3V
-
2.4
3.0
mA
VR_ON = 0V, VDD = 5.0V
-
-
1.0
µA
-
4.35
4.50
V
3.85
4.10
-
V
VID<4:0> = 00000
-
1.28750
-
V
VID<4:0> = 11111
-
0.41200
-
V
VID<4:0> = 00000 to 11110 (1.28750V to
0.51500V)
-
25.75
-
mV/step
VID<4:0> = 11110 to 11111 (0.51500V to
0.41200V)
-
103
-
mV
VID = 1.28750V to 0.74675V
TA = 0°C to +100°C
-0.5
-
0.5
%
VID = 0.72100V to 0.51500V
TA = 0°C to +100°C
-1.0
-
1.0
%
VID = 0.41200
TA = 0°C to +100°C
-2.0
-
2.0
%
RFSET = 7kΩ, VCOMP = 2V
318
333
348
kHz
TEST CONDITIONS
VIN
VIN Input Resistance
R VIN
VIN Shutdown Current
IVIN_SHDN
VDD and PVCC
VDD Input Bias Current
IVDD
VDD Shutdown Current
IVDD_SHDN
VDD POR THRESHOLD
Rising VDD POR Threshold Voltage
V
Falling VDD POR Threshold Voltage
V
VDD_THR
VDD_THF
REGULATION
V
Output Voltage Range
GFX_MAX
V
GFX_MIN
VID Voltage Step
System Accuracy
PWM
F
Nominal Frequency
SW
6
FN9213.2
June 10, 2010
ISL6263
Electrical Specifications
These specifications apply for TA = -10°C to +100°C, unless otherwise stated. All typical specifications
TA = +25°C, VDD = 5V, PVCC = 5V. Boldface limits apply over the operating temperature range,
-10°C to +100°C. (Continued)
PARAMETER
SYMBOL
TEST CONDITIONS
Frequency Range
MIN
(Note 6)
TYP
MAX
(Note 6)
UNITS
200
-
500
kHz
-
90
-
dB
AMPLIFIERS
Error Amplifier DC Gain (Note 8)
AV0
Error Amplifier Gain-Bandwidth Product
(Note 8)
GBW
CL = 20pF
-
18
-
MHz
SR
CL = 20pF
-
5
-
V/µs
IFB
VFB = 1.28750V
-
10
150
nA
Error Amp Slew Rate (Note 8)
FB Input Bias Current
V
Droop Amplifier Offset
V
RBIAS Voltage
RBIAS
I
I2UA Reference Current
-0.3
-
0.3
mV
R
RBIAS =150kΩ
1.50
1.52
1.54
V
V
I2UA = 2.5V
1.85
2.00
2.15
µA
-46
-41
-36
µA
DROOP_OFS
I2UA
SOFT-START CURRENT
Soft-Start Current
ISS
Soft Dynamic VID Current
IDVID
|SOFT - REF|>100mV
±175
±200
±225
µA
UGATE Source Resistance
RUGSRC
500mA Source Current
-
1.0
1.5
Ω
UGATE Source Current (Note 7)
IUGSRC
VUGATE_PHASE = 2.5V
-
2.0
-
A
UGATE Sink Resistance
RUGSNK
500mA Sink Current
-
1.0
1.5
Ω
UGATE Sink Current (Note 7)
IUGSNK
VUGATE_PHASE = 2.5V
-
2.0
-
A
LGATE Source Resistance
RLGSRC
500mA Source Current
-
1.0
1.5
Ω
LGATE Source Current (Note 7)
ILGSRC
VLGATE_PGND = 2.5V
-
2.0
-
A
LGATE Sink Resistance
RLGSNK
500mA Sink Current
-
0.5
0.9
Ω
LGATE Sink Current (Note 7)
ILGSNK
VLGATE_PGND = 2.5V
-
4.0
-
A
-
1.1
-
kΩ
GATE DRIVER
UGATE Pull-Down Resistor (Note 7)
RPD
UGATE Turn-On Propagation Delay
tPDRU
PVCC = 5V, UGATE open
20
30
44
ns
LGATE Turn-On Propagation Delay
tPDRL
PVCC = 5V, LGATE open
7
15
30
ns
Forward Voltage
VF
PVCC = 5V, IF = 10mA
0.56
0.69
0.76
V
Reverse Leakage
IR
VR = 16V
-
-
5.0
µA
BOOTSTRAP DIODE
POWER GOOD and PROTECTION MONITOR
PGOOD Low Voltage
VPGOOD
IPGOOD = 4mA
-
0.11
0.40
V
PGOOD Leakage Current
IPGOOD
VPGOOD = 3.3V
-1.0
-
1.0
µA
VO rising above VSOFT > 1ms
160
200
240
mV
1.525
1.550
1.575
V
9.9
10.1
10.3
µA
-3
-
3
mV
-360
-300
-240
mV
-
-
1
V
Overvoltage Threshold (VO - VSOFT)
VOVP
Severe Overvoltage Threshold
VOVPS
VO rising above 1.55V reference > 0.5µs
OCSET Reference Current
IOCSET
RRBIAS = 150kΩ
OCSET Voltage Threshold Offset
Undervoltage Threshold (VSOFT - VO)
VOCSET_OFS VDROOP rising above VOCSET > 120µs
VUVF
VO falling below VSOFT for > 1ms
CONTROL INPUTS
VR_ON Input Low
VVR_ONL
7
FN9213.2
June 10, 2010
ISL6263
Electrical Specifications
These specifications apply for TA = -10°C to +100°C, unless otherwise stated. All typical specifications
TA = +25°C, VDD = 5V, PVCC = 5V. Boldface limits apply over the operating temperature range,
-10°C to +100°C. (Continued)
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
(Note 6)
TYP
MAX
(Note 6)
UNITS
VR_ON Input High
VVR_ONH
2.3
-
-
V
AF_EN Input Low
VAF_ENL
-
-
1
V
AF_EN Input High
VAF_ENH
2.3
-
-
V
VR_ON Leakage
IVR_ONL
VVR_ON = 0V
-1.0
0
-
µA
IVR_ONH
VVR_ON = 3.3V
-
0
1.0
µA
IAF_ENL
VAF_EN = 0V
-1.0
0
-
µA
IAF_ENH
VAF_EN = 3.3V
-
0.45
1.0
µA
AF_EN Leakage
VID<4:0> Input Low
VVIDL
-
-
0.3
V
VID<4:0> Input High
VVIDH
0.7
-
-
V
FDE Input Low
VFDEL
-
-
0.3
V
FDE Input High
VFDEH
0.7
-
-
V
-1.0
0
-
µA
VID<4:0> Leakage
FDE Leakage
IVIDL
VVID = 0V
IVIDH
VVID = 1.0V
-
0.45
1.0
µA
IFDEL
VFDE = 0V
-1.0
0
-
µA
IFDEH
VFDE = 1.0V
-
0.45
1.0
µA
NOTES:
6. 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.
7. Limits established by characterization and are not production tested.
8. Limits should be considered typical and are not production tested.
Functional Pin Descriptions
RBIAS (Pin 1) - Sets the internal 10µA current reference.
Connect a 150kΩ ±1% resistor from RBIAS to VSS.
SOFT (Pin 2) - Sets the output voltage slew-rate. Connect
an X5R or X7R ceramic capacitor from SOFT to VSS. The
SOFT pin is the non-inverting input of the error amplifier.
RTN (Pin 9) - This is the VSS_SNS input of the processor
socket Kelvin connection. Connects internally to one of two
inverting inputs of the VDIFF differential-summing amplifier.
DROOP (Pin 10) - Connects to the output of the droop
differential amplifier and to one of two non-inverting inputs of
the VDIFF differential-summing amplifier.
OCSET (Pin 3) - Sets the overcurrent threshold. Connect a
resistor from OCSET to VO.
DFB (Pin 11) - This is the feedback of the droop amplifier.
Connects internally to the inverting input of the droop
differential amplifier.
VW (Pin 4) - Sets the static PWM switching frequency in
continuous conduction mode. Connect a resistor from VW to
COMP.
VO (Pin 12) - Connects to one of two inverting inputs of the
VDIFF differential-summing amplifier.
COMP (Pin 5) - Connects to the output of the control loop
error amplifier.
FB (Pin 6) - Connects to the inverting input of the control
loop error amplifier.
VDIFF (Pin 7) - Connects to the output of the VDIFF
differential-summing amplifier.
VSEN (Pin 8) - This is the VCC_SNS input of the processor
socket Kelvin connection. Connects internally to one of two
non-inverting inputs of the VDIFF differential-summing
amplifier.
8
VSUM (Pin 13) - Connects to the non-inverting input of the
droop differential amplifier.
VIN (Pin 14) - Connects to the R3 PWM modulator providing
input voltage feed-forward. For optimum input voltage
transient response, connect near the drain of the high-side
MOSFETs.
VSS (Pin 15) - Analog ground.
VDD (Pin 16) - Input power supply for the IC. Connect to
+5VDC and decouple with at least a 1µF MLCC capacitor
from the VDD pin to the VSS pin.
FN9213.2
June 10, 2010
ISL6263
PHASE (Pin 19) - Current return path for the UGATE highside MOSFET gate driver. Detects the polarity of the PHASE
node voltage for diode emulation. Connect the PHASE pin to
the drains of the low-side MOSFETs.
PGND (Pin 20) - Current return path for the LGATE low-side
MOSFET gate driver. The PGND pin only conducts current
when LGATE pulls down. Connect the PGND pin to the
sources of the low-side MOSFETs.
LGATE (Pin 21) - Low-side MOSFET gate driver output.
Connect to the gate of the low-side MOSFET.
RENDER
MODE
PERFORMANCE
UGATE (Pin 18) - High-side MOSFET gate driver output.
Connect to the gate of the high-side MOSFET.
TABLE 1. FDE AND AF_EN STATE TABLE
SUSPEND
BOOT (Pin 17) - Input power supply for the high-side
MOSFET gate driver. Connect an MLCC bootstrap capacitor
from the BOOT pin to the PHASE pin.
FDE
AF_EN
PWM
MODE
Δ VW
AUDIO
FILTER
0
0
CCM
x
x
1
0
CCM/DCM
x
x
0
1
CCM
x
x
1
1
CCM/DCM
x
x
0
0
CCM/DCM
+33%
Off
1
0
CCM/DCM
+33%
Off
0
1
CCM/DCM
None
On
1
1
CCM/DCM
None
Off
TABLE 2. VID TABLE FOR INTEL IMVP-6+ VCCGFX
CORE
VID4
VID3
VID2
VID1
VID0
VCCGFX
(V)
x
x
x
x
x
0
0
0
0
0
0
1.28750
0
0
0
0
1
1.26175
0
0
0
1
0
1.23600
VID0:VID4 (Pin 23:Pin 27) - Voltage identification inputs.
VID0 input is the least significant bit (LSB) and VID4 input is
the most significant bit (MSB).
0
0
0
1
1
1.21025
0
0
1
0
0
1.18450
0
0
1
0
1
1.15875
0
0
1
1
0
1.13300
0
0
1
1
1
1.10725
0
1
0
0
0
1.08150
0
1
0
0
1
1.05575
0
1
0
1
0
1.03000
0
1
0
1
1
1.00425
0
1
1
0
0
0.97850
0
1
1
0
1
0.95275
0
1
1
1
0
0.92700
0
1
1
1
1
0.90125
1
0
0
0
0
0.87550
1
0
0
0
1
0.84975
I2UA (Pin 28) - Output of an internal 2µA current source.
Connect a 20kΩ resistor from the I2UA pin to the VSS pin.
VR_ON (Pin 29) - A high logic signal on this pin enables the
converter and a low logic signal disables the converter.
AF_EN (Pin 30) - A high logic signal on this pin enables the
audible frequency filter. A low logic signal on this pin
disables the audible frequency filter and improves the
converter efficiency.
PGOOD (Pin 31) - The PGOOD pin is an open-drain output
that indicates when the converter is able to supply regulated
voltage. Connect the PGOOD pin to a maximum of 5V
through a pull-up resistor.
FDE (Pin 32) - A low logic state on this pin confines the
availability of diode emulation mode to Render Suspend VID
states only. A high logic state on this pin enables diode
emulation for all VID states.
9
RENDER PERFORMANCE STATES
PVCC (Pin 22) - Input power supply for the low-side
MOSFET gate driver, and the high-side MOSFET gate
driver, via the internal bootstrap diode connected between
the PVCC and BOOT pins. Connect to +5VDC and decouple
with at least 1µF of an MLCC capacitor from the PVCC pin to
the PGND pin.
FN9213.2
June 10, 2010
ISL6263
Power-On Reset
RENDER SUSPEND STATES
TABLE 2. VID TABLE FOR INTEL IMVP-6+ VCCGFX
CORE (Continued)
VID4
VID3
VID2
VID1
VID0
VCCGFX
(V)
1
0
0
1
0
0.82400V
1
0
0
1
1
0.79825V
The ISL6263 is disabled until the voltage at the VDD pin has
increased above the rising VDD power-on reset (POR)
VDD_THR threshold voltage. The controller will become
disabled when the voltage at the VDD pin decreases below
the falling POR VDD_THF threshold voltage.
1
0
1
0
0
0.77250V
Start-Up Timing
1
0
1
0
1
0.74675V
1
0
1
1
0
0.72100V
1
0
1
1
1
0.69525V
1
1
0
0
0
0.66950V
1
1
0
0
1
0.64375V
1
1
0
1
0
0.61800V
1
1
0
1
1
0.59225V
1
1
1
0
0
0.56650V
1
1
1
0
1
0.54075V
1
1
1
1
0
0.51500V
1
1
1
1
1
0.41200V
Figure 4 shows the ISL6263 start-up timing. Once VDD has
ramped above VDD_THR, the controller can be enabled by
pulling the VR_ON pin voltage above the input-high
threshold VVR_ONH. Approximately 100µs later, the soft-start
capacitor CSOFT begins slewing to the designated VID
set-point as it is charged by the soft-start current source ISS.
The VCCGFX output voltage of the converter follows the
VSOFT voltage ramp to within 10% of the VID set-point then
counts 6 switching cycles, then changes the open-drain
output of the PGOOD pin to high impedance. During
soft-start, the regulator always operates in continuous
conduction mode (CCM).
VR_ON
Theory of Operation
90%
~100µs
The R3 Modulator
The heart of the ISL6263 is Intersil’s Robust-RippleRegulator (R3) Technology™. The R3 modulator is a hybrid
of fixed frequency PWM control, and variable frequency
hysteretic control that will simultaneously affect the PWM
switching frequency and PWM duty cycle in response to
input voltage and output load transients.
The term “Ripple” in the name “Robust-Ripple-Regulator”
refers to the synthesized voltage-ripple signal VR that
appears across the internal ripple-capacitor CR. The V R
signal is a representation of the output inductor ripple
current. Transconductance amplifiers measuring the input
voltage of the converter and the output set-point voltage
VSOFT, together produce the voltage-ripple signal VR.
A voltage window signal V W is created across the VW and
COMP pins by sourcing a current proportional to gmVsoft
through a parallel network consisting of resistor RFSET and
capacitor CFSET. The synthesized voltage-ripple signal VR
along with similar companion signals are converted into
PWM pulses.
The PWM frequency is proportional to the difference in
amplitude between V W and VCOMP. Operating on these
large-amplitude, low noise synthesized signals allows the
ISL6263 to achieve lower output ripple and lower phase jitter
than either conventional hysteretic or fixed frequency PWM
controllers. Unlike conventional hysteretic converters, the
ISL6263 has an error amplifier that allows the controller to
maintain tight voltage regulation accuracy throughout the
VID range from 0.41200V to 1.28750V.
10
VSOFT/VCCGFX
PGOOD
6 SWITCHING CYCLES
FIGURE 4. ISL6263 START-UP TIMING
Static Regulation
The VCCGFX output voltage will be regulated to the value set
by the VID inputs per Table 2. A true differential amplifier
connected to the VSEN and RTN pins implements processor
socket Kelvin sensing for precise core voltage regulation at
the GPU voltage sense points.
As the load current increases from zero, the VCCGFX output
voltage will droop from the VID set-point by an amount
proportional to the IMVP-6+ load line. The ISL6263 can
accommodate DCR current sensing or discrete resistor
current sensing. The DCR current sensing uses the intrinsic
series resistance of the output inductor as shown in the
application circuit of Figure 2. The discrete resistor current
sensing uses a shunt connected in series with the output
inductor as shown in the application circuit of Figure 3. In
both cases the signal is fed to the non-inverting input of the
DROOP amplifier at the VSUM pin, where it is measured
differentially with respect to the output voltage of the
converter at the VO pin and amplified. The voltage at the
FN9213.2
June 10, 2010
ISL6263
sensing allows the voltage regulator to tightly control the
processor voltage at the die, compensating for various
resistive voltage drops in the power delivery path.
DROOP pin minus the output voltage measured at the VO
pin, is proportional to the total inductor current. This
information is used exclusively to achieve the IMVP-6+ load
line as well as the overcurrent protection. It is important to
note that this current measurement should not be confused
with the synthetic current ripple information created within
the R3 modulator.
Since the voltage feedback is sensed at the processor die,
removing the GPU will open the voltage feedback path of the
regulator, causing the output voltage to rise towards VIN.
The ISL6263 will shut down when the voltage between the
VO and VSS pins exceeds the severe overvoltage protection
threshold VOVPS of 1.55V. To prevent this issue from
occurring, it is recommended to install resistors Ropn1 and
Ropn2 as shown in Figure 5. These resistors provide voltage
feedback from the regulator local output in the absence of
the GPU. These resistors should be in the range of 20Ω to
100Ω.
When using inductor DCR current sensing, an NTC element
is used to compensate the positive temperature coefficient of
the copper winding thus maintaining the load-line accuracy.
Processor Socket Kelvin Voltage Sensing
The remote voltage sense input pins VSEN and RTN of the
ISL6263 are to be terminated at the die of the GPU through
connections that mate at the processor socket. (The signal
names are Vcc_sense and Vss_sense respectively.) Kelvin
VDD
+
+
DROOP
−
VSUM
ESR
DFB
RDRP1
CDRP
+
Σ
+
CFILTER1
VSEN
+
RFILTER1
VCC_SNS
RFILTER2
RTN
−
RNTC
VO
−
CN
RDRP2
DROOP
+
COUT
RS
RNTCP
−
OCP
ROCSET
ROPN1
OCSET
VDIFF
CFILTER2
CFILTER3
VSS_SNS
ROPN2
↓
DCR
PHASE
RNTCS
10µA
LOUT
To
Processor
Socket
Kelvin
Connections
FIGURE 5. SIMPLIFIED VOLTAGE DROOP CIRCUIT WITH GPU SOCKET KELVIN SENSING AND INDUCTOR DCR CURRENT SENSING
High Efficiency Diode Emulation Mode
The ISL6263 operates in continuous-conduction-mode
(CCM) during heavy load for minimum conduction loss by
forcing the low-side MOSFET to operate as a synchronous
rectifier. Depending upon the VID and FDE pin states, an
improvement in light-load efficiency can be achieved by
operating in discontinuous-conduction-mode (DCM) where
the low-side MOSFET is operated in diode-emulation-mode
(DEM), forcing the low-side MOSFET to block negative
inductor current flow.
Positive-going inductor current flows from either the source
of the high-side MOSFET, or the drain of the low-side
MOSFET. Negative-going inductor current flows into the
11
source of the high-side MOSFET, or the drain of the low-side
MOSFET. When the low-side MOSFET conducts positive
inductor current, the phase voltage will be negative with
respect to the VSS pin. Conversely, when the low-side
MOSFET conducts negative inductor current, the phase
voltage will be positive with respect to the VSS pin. Negative
inductor current occurs in CCM when the output load current
is less than ½ the inductor ripple current. Sinking negative
inductor through the low-side MOSFET lowers efficiency
through unnecessary conduction losses. Upon entering
DEM the PWM switching frequency is automatically shifted
downward by an increase of the window voltage V W of 33%.
The PWM switching frequency will continue to decrease as
the load continues to decrease. The reduction of PWM
FN9213.2
June 10, 2010
ISL6263
frequency further improves efficiency by reducing switching
losses. The converter will automatically enter DEM after
eight consecutive PWM pulses where the PHASE pin has
detected positive voltage shortly after the LGATE pin has
gone high. The converter will return to CCM on the following
cycle after the PHASE pin detects negative voltage shortly
after the LGATE pin has gone high, indicating that the body
diode of the low-side MOSFET is conducting positive
inductor current. The converter inhibits the automatic 33%
change of V W whenever the audio filter is enabled.
Smooth mode transitions are facilitated by the R3 modulator
which correctly maintains the internally synthesized ripple
current information throughout mode transitions.
Protection
The ISL6263 provides overcurrent protection (OCP),
overvoltage protection (OVP), and undervoltage protection
(UVP) as shown in Table 3.
Overcurrent protection is tied to the voltage droop, which is
determined by the resistors selected in the Static Droop
Design Using DCR Sensing section. After the load line is set,
the OCSET resistor can be selected. The OCP threshold
detector is checked every 15µs and will increment a counter
if the OCP threshold is exceeded, conversely the counter will
be decremented if the load current is below the OCP
threshold. The counter will latch an OCP fault when the
counter reaches eight. The fastest OCP response for
overcurrent events occurring above the OCP threshold but
below twice the OCP threshold is 120µs, which is eight
counts at 15µs each. The ISL6263 will latch an OCP fault
within 2µs for an overcurrent exceeding twice the OCP
threshold to maximize protection against hard shorts. The
value of ROCSET is calculated as Equation 1:
I OC ⋅ R droop
R OCSET = ---------------------------------10μA
(EQ. 1)
For example: The desired overcurrent trip level, Ioc, is 30A,
Rdroop load-line is 8mΩ, Equation 1 gives ROCSET = 24kΩ.
Undervoltage protection is independent of the overcurrent
protection. If the output voltage measured on the VO pin is
less than +300mV below the voltage on the SOFT pin for
longer than 1ms, the controller will latch a UVP fault. If the
output voltage measured on the VO pin is greater than
+200mV above the voltage on the SOFT pin for longer than
1ms, the controller will latch an OVP fault. Keep in mind that
VSOFT will equal the voltage level commanded by the VID
states only after the soft-start capacitor CSOFT has slewed to
the VID DAC output voltage. The UVP and OVP detection
circuits act on static and dynamic VSOFT voltage.
When an OCP, OVP, or UVP fault has been latched, PGOOD
becomes a low impedance and the gate driver outputs
UGATE and LGATE are pulled low. The energy stored in the
inductor is dissipated as current flows through the low-side
12
MOSFET body diode. The controller will remain latched in
the fault state until the VR_ON pin has been pulled below the
falling VR_ON threshold voltage VVR_ONL or until VDD has
gone below the falling POR threshold voltage VVDD_THF.
A severe-overvoltage protection fault occurs immediately
after the voltage between the VO and VSS pins exceed the
rising severe-overvoltage threshold VOVPS which is 1.545V,
the same reference voltage used by the VID DAC. The
ISL6263 will latch UGATE and PGOOD low but unlike other
protective faults, LGATE remains high until the voltage
between VO and VSS falls below approximately 0.77V, at
which time LGATE is pulled low. The LGATE pin will continue
to switch high and low at 1.545V and 0.77V until VDD has
gone below the falling POR threshold voltage VVDD_THF.
This provides maximum protection against a shorted highside MOSFET while preventing the output voltage from
ringing below ground. The severe-overvoltage fault circuit
can be triggered after another fault has already been
latched.
TABLE 3. FAULT PROTECTION SUMMARY OF ISL6263
FAULT TYPE
FAULT
DURATION
PRIOR TO
PROTECTION
PROTECTION
ACTIONS
FAULT
RESET
Overcurrent
120µs
LGATE, UGATE, and Cycle
PGOOD latched low VR_ON or
VDD
Short Circuit
<2µs
LGATE, UGATE, and Cycle
PGOOD latched low VR_ON or
VDD
Overvoltage
(+200mV)
between VO pin
and SOFT pin
1ms
LGATE, UGATE, and Cycle
PGOOD latched low VR_ON or
VDD
Severe
Overvoltage
(+1.55V)
between VO pin
and VSS pin
Immediately
Cycle
UGATE, and
PGOOD latched low, VDD only
LGATE toggles ON
when VO>1.55V
OFF when
VO <0.77V
until fault reset
Undervoltage
(-300mV)
between VO pin
and SOFT pin
1ms
LGATE, UGATE, and Cycle
PGOOD latched low VR_ON or
VDD
Gate-Driver Outputs LGATE and UGATE
The ISL6263 has internal high-side and low-side N-Channel
MOSFET gate-drivers. The LGATE driver is optimized for
low duty-cycle applications where the low-side MOSFET
conduction losses are dominant. The LGATE pull-down
resistance is very low in order to clamp the gate-source
voltage of the MOSFET below the VGS(th) at turnoff. The
current transient through the low-side gate at turnoff can be
considerable due to the characteristic large switching charge
of a low r DS(on) MOSFET.
FN9213.2
June 10, 2010
ISL6263
Adaptive shoot-through protection prevents the gate-driver
outputs from going high until the opposite gate-driver output
has fallen below approximately 1V. The UGATE turn-on
propagation delay tPDRU and LGATE turn-on propagation
delay tPDRL are found in the Electrical Specifications table.
The power for the LGATE gate-driver is sourced directly from
the PVCC pin. The power for the UGATE gate-driver is
sourced from a boot-strap capacitor connected across the
BOOT and PHASE pins. The boot capacitor is charged from
PVCC through an internal boot-strap diode each time the
low-side MOSFET turns on, pulling the PHASE pin low.
PWM
LGATE
1V
UGATE
1V
t PDRU
t PDRL
FIGURE 6. GATE DRIVER TIMING DIAGRAM
Internal Bootstrap Diode
The ISL6263 has an integrated boot-strap Schottky diode
connected from the PVCC pin to the BOOT pin. Simply
adding an external capacitor across the BOOT and PHASE
pins completes the bootstrap circuit.
2.0
1.8
CBOOT_CAP (µF)
1.6
1.4
As an example, suppose an upper MOSFET has a gate
charge, QGATE , of 25nC at 5V and also assume the droop in
the drive voltage at the end of a PWM cycle is 200mV. One
will find that a bootstrap capacitance of at least 0.125µF is
required. The next larger standard value capacitance is
0.15µF. A good quality ceramic capacitor is recommended.
Soft-Start and Soft Dynamic VID Slew Rates
The output voltage of the converter tracks VSOFT, the
voltage across the SOFT and VSS pins. Shown in Figure 1,
the SOFT pin is connected to the output of the VID DAC
through the unidirectional soft-start current source ISS or the
bidirectional soft-dynamic VID current source IDVID, and the
non-inverting input of the error amplifier. Current is sourced
from the SOFT pin when ISS is active. The SOFT pin can
both source and sink current when IDVID is active. The
soft-start capacitor CSOFT changes voltage at a rate
proportional to ISS or IDVID. The ISL6263 automatically
selects ISS for the soft-start sequence so that the inrush
current through the output capacitors is maintained below
the OCP threshold. Once soft-start has completed, IDVID is
automatically selected for output voltage changes
commanded by the VID inputs, charging CSOFT when the
output voltage is commanded to rise, and discharging
CSOFT when the output voltage is commanded to fall.
The IMVP-6+ Render Voltage Regulator specification
requires a minimum of 10mV/µs for SLEWRATEGFX. The
value for CSOFT must guarantee the minimum slew-rate of
10mV/µs when the soft-dynamic VID current source I DVID is
the minimum specified value in the Electrical Specifications
table. The value of CSOFT, can be calculated from
Equation 3:
I DVIDmin 175μA
C SOFT = ------------------------- = ------------------ = 0.0175μF
10K
10mV⎞
⎛ --------------⎝ μs ⎠
1.2
1.0
0.8
QGATE = 100nC
0.6
nC
50
0.4
0.2
where QGATE is the amount of gate charge required to fully
charge the gate of the upper MOSFET. The ΔVBOOT term is
defined as the allowable droop in the rail of the upper drive.
20nC
0.0
0.0
0.1
0.2
0.3
0.4 0.5 0.6 0.7
ΔVBOOT_CAP (V)
0.8
0.9
1.0
FIGURE 7. BOOTSTRAP CAPACITANCE vs BOOT RIPPLE
VOLTAGE
The minimum value of the bootstrap capacitor can be
calculated from Equation 2:
Q GATE
C BOOT ≥ -----------------------ΔV BOOT
(EQ. 2)
13
(EQ. 3)
Choosing the next lower standard component value of
0.015µF will guarantee 10mV/µs SLEWRATEGFX. This
choice of CSOFT controls the startup slew-rate as well. One
should expect the output voltage during soft-start to slew to
the voltage commanded by the VID settings at a nominal
rate given by Equation 4:
I SS
dV SOFT
41μA
2.8mV
- = ----------------------- ≈ ---------------------------------------- = -----------------dt
C SOFT 0.015μF
μs
(EQ. 4)
Note that the slewrate is the average rate of change
between the initial and final voltage values. The slewrate is
moderated as VCCGFX approaches the voltage commanded
by the VID inputs.
FN9213.2
June 10, 2010
ISL6263
RBIAS Current Reference
The RBIAS pin is internally connected to a 1.545V reference
through a 3kΩ resistance. A bias current is established by
connecting a ±1% tolerance, 150kΩ resistor between the
RBIAS and VSS pins. This bias current is mirrored, creating the
OCSET reference current I OCSET that is sourced from the
OCSET pin. Do not connect any other components to this
pin, as they will have a negative impact on the performance
of the IC.
I2UA Current Reference
The I2UA pin is connected to a 2µA current source II2UA. This
current source is made available for implementing a voltage
offset of the commanded VID states. A 20kΩ resistor RI2UA
should be connected across the I2UA and VSS pins if the II2UA
current source is unused.
Setting the PWM Switching Frequency
The R3 modulator scheme is not a fixed-frequency
architecture, lacking a fixed-frequency clock signal to
produce PWM. The switching frequency increases during
the application of a load to improve transient performance.
The static PWM frequency varies slightly depending on the
input voltage, output voltage, and output current, but this
variation is normally less than 10% in continuous conduction
mode.
Refer to Figure 2, and find that resistor R FSET is connected
between the V W and COMP pins. A current is sourced from
VW through RFSET creating the synthetic ripple window
voltage signal V W which determines the PWM switching
frequency. The relationship between the resistance of RFSET
and the switching frequency in CCM is approximately given by
Equation 5:
1
R FSET = ---------------------------------------------------–6
( T – 0.29 ×10 ) ⋅ 47
(EQ. 5)
For example, the value of RFSET for 300kHz operation is
approximately:
3
1
7 ×10 = ---------------------------------------------------------------------------–6
–6
( 3.33 ×10 – 0.29 ×10 ) ⋅ 47
(EQ. 6)
This relationship only applies to operation in constant
conduction mode because the PWM frequency naturally
decreases as the load decreases while in diode emulation
mode. Note that the Electrical Specifications table gives the
nominal PWM frequency of 333kHz with RFSET = 7kΩ,
different from the result of equation Equation 6. This is
because the IC is trimmed with VCOMP = 2V which is higher
than the typical value encountered in a typical application.
Static Droop Design Using DCR Sensing
The ISL6263 has an internal differential amplifier to
accurately regulate the voltage at the processor die.
For DCR sensing, the process to compensate the DCR
resistance variation takes several iterative steps. Figure 2
14
shows the DCR sensing method. Figure 8 shows the
simplified model of the droop circuitry. The inductor DC
current generates a DC voltage drop on the inductor DCR.
Equation 7 gives this relationship:
V DCR = I o ⋅ DCR
(EQ. 7)
An R-C network senses the voltage across the inductor to
get the inductor current information. RNTCEQ represents the
NTC network consisting of RNTC, RNTCS, and RNTCP. The
choice of RS will be discussed in the next section.
The first step in droop load line compensation is to adjust
RNTCEQ, and RS such that the correct droop voltage
appears even at light loads between the VSUM and VO pins.
As a rule of thumb, the voltage drop VN across the RNTCEQ
network, is set to be 0.5x to 0.8x VDCR. This gain, defined as
G1, provides a reasonable amount of light load signal from
which to derive the droop voltage.
The NTC network resistor value is dependent on
temperature and is given by Equation 8:
( R NTC + R NTCS ) ⋅ R NTCP
R N ( T ) = -----------------------------------------------------------------------R NTC + R NTCS + R NTCP
(EQ. 8)
G1, the gain of VN to VDCR, is also dependent on the
temperature of the NTC thermistor:
RN ( T )
G 1 ( T ) = ------------------------------RN ( T ) + RS
(EQ. 9)
The inductor DCR is a function of temperature and is
approximately given by Equation 10:
DCR ( T ) = DCR 25°C ⋅ ( 1 + 0.00393 ⋅ ( T – 25°C ) )
(EQ. 10)
The droop amplifier output voltage divided by the total load
current is given by Equation 11:
R droop = G 1 ( T ) ⋅ DCR 25°C ⋅ ( 1 + 0.00393 ⋅ ( T – 25°C ) ) ⋅ k droopamp
(EQ. 11)
Rdroop is the actual load line slope, and 0.00393 is the
temperature coefficient of the copper. To make Rdroop
independent of the inductor temperature, it is desired to
have Equation 12:
G 1 ( T ) ⋅ ( 1 + 0.00393 ⋅ ( T – 25°C ) ) ≅ G 1t arg et
(EQ. 12)
where G1target is the desired ratio of Vn / VDCR. Therefore,
the temperature characteristics G1 is described by
Equation 13:
G 1t arg et
G 1 ( T ) = --------------------------------------------------------------------( 1 + 0.00393 ⋅ ( T – 25°C ) )
(EQ. 13)
It is recommended to begin your droop design using the
RNTC, RNTCS, and RNTCP component values of the
evaluation board available from Intersil.
FN9213.2
June 10, 2010
ISL6263
Rdroop is 8mΩ per Intel IMVP-6+ specification and RDRP1 is
typically 1kΩ.
The gain of the droop amplifier circuit is Equation 14:
R DRP2
k droopamp = 1 + ------------------R DRP1
(EQ. 14)
The effectiveness of the RNTCEQ network is sensitive to the
coupling coefficient between the NTC thermistor and the
inductor. The NTC thermistor should be placed in the closet
proximity of the inductor.
After determining RS and RNTCEQ networks, use
Equation 15 to calculate the droop resistances RDRP1 and
RDRP2.
R droop
⎞
⎛⎛
⎞
R DRP2 = ⎜ ⎜ -------------------------------------------⎟ – 1⎟ ⋅ R DRP1
⎝ ⎝ DCR ⋅ G 1 ( 25°C )⎠
⎠
(EQ. 15)
VDD
10µA
↓
OCSET
−
OCP
+
+
DROOP
−
ROCSET
RS
VSUM
DFB
RNTCEQ
VDCR
RDRP1
CN
VO
−
RDRP2
DROOP
+
FIGURE 8. EQUIVALENT MODEL FOR DROOP CIRCUIT USING INDUCTOR DCR CURRENT SENSING
VDD
↓
OCSET
OCP
+
+
RS
VSUM
DFB
DROOP
VO
VRSNS
RDRP1
−
+
DROOP
−
ROCSET
CN
−
RDRP2
10µA
FIGURE 9. EQUIVALENT MODEL FOR DROOP CIRCUIT USING DISCRETE RESISTOR CURRENT SENSING
15
FN9213.2
June 10, 2010
ISL6263
To see whether the NTC network successfully compensates
the DCR change over temperature, one can apply full load
current and wait for the thermal steady state and see how
much the output voltage deviates from the initial voltage
reading. A good compensation can limit the drift to less than
2mV. If the output voltage is decreasing when the temperature
increases, that ratio between the NTC thermistor value and
the rest of the resistor divider network has to be increased.
Following the evaluation board value and layout of NTC
placement will minimize the engineering time.
The current sensing traces should be routed directly to the
inductor pads for accurate DCR voltage drop measurement.
However, due to layout imperfection, the calculated RDRP2
may still need slight adjustment to achieve optimum load line
slope. It is recommended to adjust RDRP2 after the system
has achieved thermal equilibrium at full load. For example, if
the maximum load current is 20A, one should apply a 20A
load current and look for 160mV output voltage droop. If the
voltage droop is 155mV, the new value of RDRP2 is
calculated by Equation 16:
160mV
R DRP2new = ------------------- ⋅ ( R DRP1 – R DPR2 ) – R DRP1
155mV
Vcore
icore
ΔIcore
Vcore
ΔVcore
ΔVcore= ΔIcore×Rdroop
FIGURE 10. DESIRED LOAD TRANSIENT RESPONSE
WAVEFORMS
icore
Vcore
Vcore
FIGURE 11. LOAD TRANSIENT RESPONSE WHEN CN IS TOO
SMALL
(EQ. 16)
For the best accuracy, the effective resistance on the DFB
and VSUM pins should be identical so that the bias current
of the droop amplifier does not cause an offset voltage.
Dynamic Droop Capacitor Design Using DCR
Sensing
Figure 10 shows the desired waveforms during load
transient response. VCCGFX needs to follow the change in
Icore as close as possible. The transient response of
VCCGFX is determined by several factors, namely the choice
of output inductor, output capacitor, compensator design,
and the design of droop capacitor CN.
If CN is designed correctly, the voltage VDROOP -VO will be
an excellent representation of the inductor current. Given the
correct CN design, VCCGFX has the best chance of tracking
ICORE, if not, its voltage will be distorted from the actual
waveform of the inductor current and worsens the transient
response. Figure 11 shows the transient response when CN
is too small allowing VCCGFX to sag excessively during the
load transient. Figure 12 shows the transient response when
CN is too large. VCCGFX takes too long to droop to its final
value.
icore
Vcore
Vcore
FIGURE 12. LOAD TRANSIENT RESPONSE WHEN CN IS TOO
LARGE
The current sensing network consists of RNTCEQ, RS, and
CN. The effective resistance is the parallel of RNTCEQ and
RS. The RC time constant of the current sensing network
needs to match the L/DCR time constant of the inductor to
get the correct representation of the inductor current
waveform. Equation 17 shows this relationship:
⎛ R NTCEQ ⋅ R S ⎞
L
-⎟ ⋅ C N
------------- = ⎜ -------------------------------------DCR
⎝ R NTCEQ + R S⎠
(EQ. 17)
Solution of CN yields Equation 18:
L ⎞
⎛ ------------⎝ DCR⎠
C N = -------------------------------------------⎛ R NTCEQ ⋅ R S ⎞
⎜ ---------------------------------------⎟
⎝ R NTCEQ + R S⎠
(EQ. 18)
For example: L = 0.45µH, DCR = 1.1mΩ, RS = 7.68kΩ, and
RNTCEQ = 3.4kΩ:
0.45μH⎞
⎛ ------------------⎝ 1.1mΩ ⎠
C N = ------------------------------------------------- = 174nF
3.4kΩ ⋅ 7.68kΩ ⎞
⎛ -----------------------------------------⎝ 3.4kΩ + 7.68kΩ⎠
(EQ. 19)
Since the inductance and the DCR typically have 20% and
7% tolerance respectively, CN needs to be fine tuned on the
16
FN9213.2
June 10, 2010
ISL6263
actual board by examining the transient voltage. It is
recommended to choose the minimum capacitance based
on the maximum inductance. CN also needs to be a highgrade capacitor such as NPO/COG or X7R with tight
tolerance. The NPO/COG caps are only available in small
capacitance values. In order to use such capacitors, the
resistors and thermistors surrounding the droop voltage
sensing and droop amplifier need to be scaled up 10x to
reduce the capacitance by 10x.
Static and Dynamic Droop using Discrete Resistor
Sensing
Figure 3 shows a detailed schematic using discrete resistor
sensing of the inductor current. Figure 9 shows the
equivalent circuit. Since the current sensing resistor voltage
represents the actual inductor current information, RS and
CN simply provide noise filtering. A low ESL sensing resistor
is strongly recommended for RSNS because this parameter
is the most significant source of noise that affects discrete
resistor sensing. It is recommended to start out using 100Ω
for RS and 47pF for CN. Since the current sensing
resistance changes very little with temperature, the NTC
network is not needed for thermal compensation. Discrete
resistor sensing droop design follows the same approach as
DCR sensing. The voltage on the current sensing resistor is
given by Equation 20:
V RSNS = I o ⋅ R SNS
(EQ. 20)
Equation 21 shows the droop amplifier gain. So the actual
droop is given by:
R DRP2⎞
⎛
R droop = R SNS ⋅ ⎜ 1 + -------------------⎟
R DRP1⎠
⎝
(EQ. 21)
Solution to RDRP2 yields Equation 22:
⎛ R droop
⎞
R DRP2 = R DRP1 ⋅ ⎜ ------------------- – 1⎟
⎝ R SNS
⎠
(EQ. 22)
For example: Rdroop = 8.0mΩ, RSNS = 1.0mΩ, and
RDRP1 = 1kΩ, RDRP2 then = 7kΩ.
The current sensing traces should be routed directly to the
current sensing resistor pads for accurate measurement.
However, due to layout imperfection, the calculated RDRP2
may still need slight adjustment to achieve optimum load line
slope. It is recommended to adjust RDRP2 after the system
has achieved thermal equilibrium at full load.
Dynamic Mode of Operation - Compensation
Parameters
The voltage regulator is equivalent to a voltage source in
series with the output impedance. The voltage source is the
VID state and the output impedance is 8.0mΩ in order to
achieve the 8.0mV/A load line. It is highly recommended to
design the compensation such that the regulator output
impedance is 8.0mΩ. Intersil provides a spreadsheet to
17
calculate the compensator parameters. Caution needs to be
used in choosing the input resistor to the FB pin. Excessively
high resistance will cause an error to the output voltage
regulation due to the bias current flowing through the FB pin.
It is recommended to keep this resistor below 3kΩ.
Layout Considerations
As a general rule, power should be on the bottom layer of
the PCB and weak analog or logic signals are on the top
layer of the PCB. The ground-plane layer should be adjacent
to the top layer to provide shielding.
Inductor Current Sensing and the NTC Placement
It is crucial that the inductor current be sensed directly at the
PCB pads of the sense element, be it DCR sensed or
discrete resistor sensed. The effect of the NTC on the
inductor DCR thermal drift is directly proportional to its
thermal coupling with the inductor and thus, the physical
proximity to it.
Signal Ground and Power Ground
The ground plane layer should have a single point
connection to the analog ground at the VSS pin. The VSS
island should be located under the IC package along with
the weak analog traces and components. The paddle on the
bottom of the ISL6263 QFN package is not electrically
connected to the IC however, it is recommended to make a
good thermal connection to the VSS island using several
vias. Connect the input capacitors, the output capacitors,
and the source of the lower MOSFETs to the power ground
plane.
LGATE, PVCC, and PGND
PGND is the return path for the pull-down of the LGATE
low-side MOSFET gate driver. Ideally, PGND should be
connected to the source of the low-side MOSFET with a
low-resistance, low-inductance path. The LGATE trace
should be routed in parallel with the trace from the PGND
pin. These two traces should be short, wide, and away from
other traces because of the high peak current and extremely
fast dv/dt. PVCC should be decoupled to PGND with a
ceramic capacitor physically located as close as practical to
the IC pins.
VIAS TO
GROUND
PLANE
GND
VOUT
INDUCTOR
HIGH-SIDE
MOSFETS
PHASE
NODE
VIN
OUTPUT
CAPACITORS
SCHOTTKY
DIODE
LOW-SIDE
MOSFETS
INPUT
CAPACITORS
FIGURE 13. TYPICAL POWER COMPONENT PLACEMENT
FN9213.2
June 10, 2010
ISL6263
UGATE, BOOT, and PHASE
PHASE is the return path for the entire UGATE high-side
MOSFET gate driver. The layout for these signals require
similar treatment, but to a greater extent, than those for
LGATE, PVCC, and PGND. These signals swing from
approximately VIN to VSS and are more likely to couple into
other signals.
SOFT, OCSET, V W, COMP, FB, VDIFF, DROOP,
DFB, VO, and VSUM
The traces and components associated with these pins
require close proximity to the IC as well as close proximity to
each other. This section of the converter circuit needs to be
located above the island of analog ground with the
single-point connection to the VSS pin.
VSEN and RTN
Resistor RS
These traces should be laid out as noise sensitive. For
optimum load line regulation performance, the traces
connecting these two pins to the Kelvin sense leads of the
processor should be laid out away from rapidly rising voltage
nodes, (switching nodes) and other noisy traces. The filter
capacitors CFILTER1, CFILTER2, and CFILTER3 used in
conjunction with filter resistors RFILTER1 and RFILTER2 form
common mode and differential mode filters as shown in
Figure 8. The noise environment of the application and
actual board layout conditions will drive the extent of filter
complexity. The maximum recommended resistance for
RFILTER1 and RFILTER2 is approximately 10Ω to avoid
interaction with the 50kΩ input resistance of the remote
sense differential amplifier. The physical location of these
resistors is not as critical as the filter capacitors. Typical
capacitance values for CFILTER1, CFILTER2, and CFILTER3
range between 330pF to 1000pF and should be placed near
the IC.
Resistor RS is preferably located near the boundary
between the power ground and the island of analog ground
connected to the VSS pin.
RBIAS and I2UA
The resistors RRBIAS and RI2UA should be placed in close
proximity to the ISL6263 using a noise-free current return
path to the VSS pin.
VID<0:4>, AF_EN, PGOOD, and VR_ON
These are logic signals that do not require special attention.
FDE
This logic signal should be treated as noise sensitive and
should be routed away from rapidly rising voltage nodes,
(switching nodes) and other noisy traces.
VIN
The VIN signal should be connected near the drain of the
high-side MOSFET.
Copper Size for the Phase Node
The parasitic capacitance and parasitic inductance of the
phase node should be kept very low to minimize ringing. It is
best to limit the size of the PHASE node copper in strict
accordance with the current and thermal management of the
application. An MLCC should be connected directly across
the drain of the high-side MOSFET and the source of the
low-side MOSFET to suppress turn-off voltage spikes.
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
18
FN9213.2
June 10, 2010
ISL6263
Package Outline Drawing
L32.5x5
32 LEAD QUAD FLAT NO-LEAD PLASTIC PACKAGE
Rev 3, 4/10
4X 3.5
5.00
28X 0.50
A
B
6
PIN 1
INDEX AREA
6
PIN #1 INDEX AREA
32
25
1
5.00
24
3 .10 ± 0 . 15
17
(4X)
8
0.15
9
16
TOP VIEW
0.10 M C A B
+ 0.07
32X 0.40 ± 0.10
4 32X 0.23 - 0.05
BOTTOM VIEW
SEE DETAIL "X"
0.10 C
0 . 90 ± 0.1
C
BASE PLANE
SEATING PLANE
0.08 C
( 4. 80 TYP )
(
( 28X 0 . 5 )
SIDE VIEW
3. 10 )
(32X 0 . 23 )
C
0 . 2 REF
5
( 32X 0 . 60)
0 . 00 MIN.
0 . 05 MAX.
DETAIL "X"
TYPICAL RECOMMENDED LAND PATTERN
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 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 indentifier may be
either a mold or mark feature.
19
FN9213.2
June 10, 2010