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TE PROD CEMENT
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EPL A
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ical Sup
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ta
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IL or
Data
July 8, 2010
-INTERS
1-888Sheet
5-Bit VID Single-Phase Voltage Regulator
with Current Monitor for IMVP-6+ Santa
Rosa GPU Core
The ISL6263B IC is a Single-Phase Synchronous-Buck
PWM voltage regulator featuring Intersil’s Robust Ripple
Regulator (R3) Technology™. The ISL6263B is an
implementation of the Intel® Mobile Voltage Positioning
(IMVP) protocol for GPU Render Engine core power.
Integrated current monitor, droop amplifier, MOSFET drivers
and bootstrap diode result in smaller implementation area and
lower component cost.
ISL6263B
FN6388.3
Features
• 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
• Real-time GPU current monitor output
• Applications up to 25A
• Input voltage range: +5.0V to +25.0V
• Programmable PWM frequency: 200kHz to 500kHz
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. For maximum conversion
efficiency, the ISL6263B automatically enters diodeemulation mode (DEM) should the inductor current attempt
to flow negative. DEM is highly configurable and easy to
set-up. A PWM filter can be enabled that prevents the
switching frequency from entering the audible spectrum as a
result of extremely light load while in DEM.
• Pre-biased output start-up capability
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
ISL6263B requires only one capacitor for both the soft-start
slew-rate and 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.
• Choice of current sensing schemes
- Lossless inductor DCR current sensing
- Precision resistive current sensing
• 5-bit voltage identification input (VID)
- 1.28750V to 0.41200V
- 25.75mV steps
- Sequential or non-sequential VID change on-the-fly
• Configurable PWM modes
- Forced continuous conduction mode
- Automatic entry and exit of diode emulation mode
- Selectable audible frequency PWM filter
• Integrated MOSFET drivers and bootstrap diode
• Overvoltage, undervoltage and overcurrent protection
• Pb-free (RoHS compliant)
Pinout
ISL6263B (32 LD 5x5 QFN)
TOP VIEW
1
IMON
VID4
VID3
VID2
28
27
26
25
RBIAS
1
24 VID1
SOFT
2
23 VID0
OCSET
3
22 PVCC
VW
4
THERMAL PAD
21 LGATE
COMP
5
(BOTTOM)
20 PGND
FB
6
19 PHASE
VDIFF
7
18 UGATE
VSEN
8
17 BOOT
9
10
11
12
13
14
15
16
VDD
3. For Moisture Sensitivity Level (MSL), please see device information
page for ISL6263B. For more information on MSL please see techbrief
TB363.
29
VSS
2. These Intersil Pb-free plastic packaged products employ special Pbfree 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.
30
VIN
1. Please refer to TB347 for details on reel specifications.
31
VSUM
NOTES:
32
VO
ISL6263BHRZ-T ISL6263 BHRZ -10 to +100 32 Ld 5x5 QFN L32.5x5
(Note 1)
Tape and Reel
VR_ON
ISL6263 BHRZ -10 to +100 32 Ld 5x5 QFN L32.5x5
AF_EN
PKG.
DWG. #
DFB
PACKAGE
(Pb-Free)
PGOOD
TEMP (°C)
DROOP
ISL6263BHRZ
PART
MARKING
RTN
PART NUMBER
(Notes 2, 3)
FDE
Ordering Information
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 trademark of Intersil Americas LLC
Copyright Intersil Americas Inc. 2007, 2008, 2010. All Rights Reserved. R3 Technology™ is a trademark of Intersil Americas LLC
All other trademarks mentioned are the property of their respective owners.
Block Diagram
VR_ON
PGOOD
BOOT
VDD
VREF
1.545V


VREF
 
1:1
VSS
2
2
SCP
UNDER
VOLTAGE

OCSET
OCP

DFB

FAULT
LATCH

VO

PVCC
LGATE
DRIVER
PGND

X31
FDE

VSEN

RTN


AF_EN
VW


VDIFF

 VW
30%

VID1
VID3
VW
R3

ISS
IDVID



VID4
PWM
MODULATOR
VID DAC

VID2
gmVIN

VID0
 VW
20%


E/A

SOFT
FB
COMP
IMON
VIN
FN6388.3
July 8, 2010
FIGURE 1. SIMPLIFIED FUNCTIONAL BLOCK DIAGRAM OF THE ISL6263B
gmVsoft VCOMP
ISL6263B
DROOP
SHOOT THROUGH
PROTECTION
SEVERE
OVERVOLTAGE
SOFT
CROWBAR
CONTROL
OVER
VOLTAGE

PHASE
AUDIBLE
FREQUENCY
FILTER
OVER
CURRENT
RBIAS
UGATE
DRIVER
DIODE
EMULATION
PGOOD
SHORT
CIRCUIT


VSUM
PWM
CONTROL
POR
ISL6263B
Simplified Application Circuit for DCR Current Sensing
RVDD
V5V
CPVCC
CVDD
VDD
PVCC
RRBIAS
RBIAS
VIN
VIN
CSOFT
QHS
SOFT
CIN
UGATE
BOOT
RIMON
PGOOD
LOUT
CBOOT
IMON
CIMON
VCCGFX
PHASE
COUT
QLS
VID<0:4>
VR_ON
LGATE
AF_EN
PGND
FDE
VCC_SNS
VSEN
VSS_SNS
RTN
RS
RNTC
VSUM
VW
ISL6263B
RFSET
RNTCP
CN
CFSET
RNTCS
VO
CCOMP1
ROCSET
RCOMP
RDRP1
OCSET
COMP
CCOMP2
DFB
FB
VDIFF
RDIFF2
RDRP2
CDIFF
CDRP
DROOP
VSS
RGND
RDIFF1
0
FIGURE 2. ISL6263B GPU RENDER-CORE VOLTAGE REGULATOR SOLUTION WITH DCR CURRENT SENSING
3
FN6388.3
July 8, 2010
ISL6263B
Simplified Application Circuit for Resistive Current Sensing
RVDD
V5V
CPVCC
CVDD
VDD
PVCC
RRBIAS
RBIAS
VIN
VIN
CSOFT
QHS
SOFT
CIN
UGATE
BOOT
RIMON
PGOOD
LOUT
CBOOT
IMON
CIMON
RSNS
VCCGFX
PHASE
VID<0:4>
COUT
QLS
VR_ON
LGATE
AF_EN
PGND
FDE
VCC_SNS
VSEN
VSS_SNS
RTN
RS
VSUM
VW
ISL6263B
RFSET
CN
CFSET
VO
CCOMP1
ROCSET
COMP
RCOMP
RDRP1
OCSET
CCOMP2
DFB
FB
VDIFF
RDIFF2
RDRP2
CDIFF
CDRP
DROOP
VSS
RGND
RDIFF1
0
FIGURE 3. ISL6263B GPU RENDER-CORE VOLTAGE REGULATOR SOLUTION WITH RESISTIVE CURRENT SENSING
4
FN6388.3
July 8, 2010
ISL6263B
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, 10J) -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, 20J) -4.0V
LGATE . . . . . . . . . . . . . . . . . . . . (DC) -0.3V to PGND, PVCC +0.3V
(<100ns Pulse Width, 4J) -2.0V
ALL Other Pins. . . . . . . . . . . . . . . . . . . . . -0.3V to VSS, VDD +0.3V
Thermal Resistance (Typical, Notes 4, 5) JA (°C/W) JC (°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. JA 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 JC, 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
TEST CONDITIONS
MIN
(Note 6)
TYP
MAX
(Note 6)
UNITS
VIN
VIN Input Resistance
R VIN
VIN Shutdown Current
IVIN_SHDN
VR_ON = 3.3V
1.0
VR_ON = 0V, VIN = 25V
M
1.0
µA
3.3
mA
1.0
µA
4.50
V
VDD and PVCC
VDD Input Bias Current
IVDD
VDD Shutdown Current
IVDD_SHDN
VR_ON = 3.3V
2.7
VR_ON = 0V, VDD = 5.0V
VDD POR THRESHOLD
Rising VDD POR Threshold Voltage
V
Falling VDD POR Threshold Voltage
V
4.35
VDD_THR
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
VDD_THF
REGULATION
V
Output Voltage Range
GFX_MAX
V
VID Voltage Step
System Accuracy
5
GFX_MIN
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
-3.0
3.0
%
FN6388.3
July 8, 2010
ISL6263B
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
318
333
348
kHz
500
kHz
PWM
f
Nominal Frequency
SW
RFSET = 7kVCOMP = 2V
Frequency Range
200
Audio Filter Frequency
F
AF
28
kHz
AV0
90
dB
AMPLIFIERS
Error Amplifier DC Gain (Note 7)
Error Amplifier Gain-Bandwidth Product
(Note 7)
GBW
CL = 20pF
18
MHz
SR
CL = 20pF
5
V/µs
IFB
VFB = 1.28750V
10
Error Amp Slew Rate (Note 7)
FB Input Bias Current
V
Droop Amplifier Offset
-0.3
DROOP_OFS
V
RBIAS Voltage
RBIAS
R
RBIAS =150k
150
nA
0.3
mV
1.495
1.515
1.535
V
-47
-42
-37
µA
SOFT-START CURRENT
Soft-Start Current
ISS
Soft Dynamic VID Current
IDVID
|SOFT - REF|>100mV
±180
±205
±230
µA
V
V
V
DROOP - O = 40mV
1.22
1.24
1.26
V
V
V
DROOP - O = 10mV
0.285
0.310
0.335
V
CURRENT MONITOR
Current Monitor Output Voltage Range
Current Monitor Maximum Output Voltage
V
IMON
IMONMAX
Current Monitor Maximum Current Sinking
Capability
3.1
3.4
VIMON/
VIMON/
VIMON/
V
250
180
130
A
Current Monitor Sourcing Current
ISC_IMON
V
V
DROOP - O = 40mV
2.0
mA
Current Monitor Sinking Current
ISK_IMON
V
V
DROOP - O = 40mV
2.0
mA
IIMON ISK_IMON, IIMON ISC_IMON
Current Monitor Impedance (Note 7)

7
GATE DRIVER

UGATE Source Resistance (Note 7)
RUGSRC
500mA Source Current
1.0
UGATE Source Current (Note 7)
IUGSRC
VUGATE_PHASE = 2.5V
2.0
UGATE Sink Resistance (Note 7)
RUGSNK
500mA Sink Current
1.0
UGATE Sink Current (Note 3)
IUGSNK
VUGATE_PHASE = 2.5V
2.0
LGATE Source Resistance (Note 7)
RLGSRC
500mA Source Current
1.0
LGATE Source Current (Note 7)
ILGSRC
VLGATE_PGND = 2.5V
2.0
LGATE Sink Resistance (Note 7)
RLGSNK
500mA Sink Current
0.5
LGATE Sink Current (Note 7)
ILGSNK
VLGATE_PGND = 2.5V
4.0
A
1.1
k
UGATE Pull-Down Resistor
RPD
1.5
A
1.5

A
1.5

A
0.9

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
0.56
0.69
0.76
V
5.0
µA
BOOTSTRAP DIODE
Forward Voltage
VF
PVCC = 5V, IF = 10mA
Reverse Leakage
IR
VR = 16V
6
FN6388.3
July 8, 2010
ISL6263B
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
0.11
0.40
V
1.0
µA
POWER GOOD and PROTECTION MONITOR
PGOOD Low Voltage
VPGOOD
IPGOOD = 4mA
PGOOD Leakage Current
IPGOOD
VPGOOD = 3.3V
-1.0
155
195
235
mV
1.525
1.550
1.575
V
9.9
10.1
10.3
µA
3
mV
-240
mV
1
V
Overvoltage Threshold (VO-VSOFT)
VOVP
VO rising above VSOFT > 1ms
Severe Overvoltage Threshold
VOVPS
VO rising above 1.55V reference > 0.5µs
OCSET Reference Current
IOCSET
RRBIAS = 150k
OCSET Voltage Threshold Offset
Undervoltage Threshold (VSOFT-VO)
VOCSET_OFS VDROOP rising above VOCSET > 120µs
VUVF
VO falling below VSOFT for > 1ms
-3
-360
-300
CONTROL INPUTS
VR_ON Input Low
VVR_ONL
VR_ON Input High
VVR_ONH
AF_EN Input Low
VAF_ENL
AF_EN Input High
VAF_ENH
VR_ON Leakage
IVR_ONL
VVR_ON = 0V
IVR_ONH
VVR_ON = 3.3V
IAF_ENL
VAF_EN = 0V
IAF_ENH
VAF_EN = 3.3V
AF_EN Leakage
VID<4:0> Input Low
VVIDL
VID<4:0> Input High
VVIDH
FDE Input Low
VFDEL
FDE Input High
VFDEH
VID<4:0> Leakage
FDE Leakage
2.3
V
1
2.3
-1.0
V
0
0
-1.0
µA
1.0
0
0.45
1.0
µA
0.4
V
V
0.3
0.7
VVID = 0V
IVIDH
VVID = 1.0V
IFDEL
VFDE = 0V
IFDEH
VFDE = 1.0V
-1.0
V
V
0
0.45
-1.0
µA
µA
0.7
IVIDL
V
µA
1.0
0
0.45
µA
µA
1.0
µA
NOTE:
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.
7
FN6388.3
July 8, 2010
ISL6263B
Functional Pin Descriptions
RBIAS (Pin 1) - Sets the internal 10µA current reference.
Connect a 150k±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.
OCSET (Pin 3) - Sets the overcurrent threshold. Connect a
resistor from OCSET to VO.
VW (Pin 4) - Sets the static PWM switching frequency in
continuous conduction mode. Connect a resistor from VW to
COMP.
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.
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.
DFB (Pin 11) - This is the feedback of the droop amplifier.
Connects internally to the inverting input of the droop
differential amplifier.
VO (Pin 12) - Connects to one of two inverting inputs of the
VDIFF differential-summing amplifier.
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.
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.
PHASE (Pin 19) - Current return path for the UGATE
high-side 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.
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.
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).
IMON (Pin 28) - A voltage signal proportional to the output
current of the converter.
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) - Used in conjunction with VID0:VID4 and
FDE pins to program the diode-emulation and audio filter
behavior. Refer to Table 1.
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) - Used in conjunction with VID0:VID4 and
AF_EN pins to program the diode-emulation and audio filter
behavior. Refer to Table 1.
BOTTOM - Connects to substrate. Electrically isolated but
should be connected to VSS. Requires best practical
thermal coupling to PCB.
TABLE 1. DIODE-EMULATION MODE AND AUDIO-FILTER
RENDER
MODE
PERFORMANCE
SUSPEND
FDE AF_EN
DEM
STATUS
VOLTAGE
WINDOW
AUDIO
FILTER
0
-
DISABLED
NOM
-
1
-
ENABLED
130% NOM
-
-
0
ENABLED
150% NOM
-
1
1
ENABLED
130% NOM
-
0
1
ENABLED
130% NOM
ENABLED
UGATE (Pin 18) - High-side MOSFET gate driver output.
Connect to the gate of the high-side MOSFET.
8
FN6388.3
July 8, 2010
ISL6263B
RENDER SUSPEND STATES
RENDER PERFORMANCE STATES
TABLE 2. VID TABLE FOR INTEL IMVP-6+
VCCGFX CORE
Theory of Operation
VID4
VID3
VID2
VID1
VID0
VCCGFX
(V)
-
-
-
-
-
0
0
0
0
0
0
1.28750
0
0
0
0
1
1.26175
0
0
0
1
0
1.23600
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
1
0
0
1
0
0.82400
1
0
0
1
1
0.79825
1
0
1
0
0
0.77250
1
0
1
0
1
0.74675
1
0
1
1
0
0.72100
1
0
1
1
1
0.69525
1
1
0
0
0
0.66950
1
1
0
0
1
0.64375
1
1
0
1
0
0.61800
1
1
0
1
1
0.59225
1
1
1
0
0
0.56650
1
1
1
0
1
0.54075
1
1
1
1
0
0.51500
1
1
1
1
1
0.41200
9
The R3 Modulator
The heart of the ISL6263B 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
ISL6263B to achieve lower output ripple and lower phase
jitter than either conventional hysteretic or fixed frequency
PWM controllers. Unlike conventional hysteretic converters,
the ISL6263B has an error amplifier that allows the controller
to maintain tight voltage regulation accuracy throughout the
VID range from 0.41200V to 1.28750V.
Power-On Reset
The ISL6263B 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.
Start-Up Timing
Figure 4 shows the ISL6263B 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 13 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).
FN6388.3
July 8, 2010
ISL6263B
VR_ON
90%
~100µs
VSOFT/VCCGFX
PGOOD
regulator, causing the output voltage to rise towards VIN.
The ISL6263B 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 20 to
100
High Efficiency Diode Emulation Mode
13 SWITCHING CYCLES
FIGURE 4. ISL6263B 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 ISL6263B 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
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.
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
ISL6263B 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
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.
Since the voltage feedback is sensed at the processor die,
removing the GPU will open the voltage feedback path of the
10
The ISL6263B 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. An improvement in light-load efficiency is achieved
by allowing the converter to operate in diode-emulation
mode (DEM) where the low-side MOSFET behaves as a
smart-diode, forcing the device 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
source of the high-side MOSFET, or into 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 when the output DC load current is
less than ½ the inductor ripple current. Sinking negative
inductor current through the low-side MOSFET lowers
efficiency through unnecessary conduction losses. Efficiency
can be further improved with a reduction of unnecessary
switching losses by reducing the PWM frequency. The PWM
frequency can be configured to automatically make a
step-reduction upon entering DEM by forcing a
step-increase of the window voltage V W. The window
voltage can be configured to increase approximately 30%,
50%, or not at all. The characteristic PWM frequency
reduction, coincident with decreasing load, is accelerated by
the step-increase of the window voltage. An audio filter can
be enabled that briefly turns on the low-side MOSFET gate
driver LGATE approximately every 35s.
The converter will enter DEM after detecting three
consecutive PWM pulses with negative inductor current. The
negative inductor current is detected during the time that the
high-side MOSFET gate driver output UGATE is low, with the
exception of a brief blanking period. The voltage between
the PHASE pin and VSS pin is monitored by a comparator
that latches upon detection of positive phase voltage. The
converter will return to CCM after detecting three
consecutive PWM pulses with positive inductor current.
The inductor current is considered positive if the phase
comparator has not been latched while UGATE is low.
FN6388.3
July 8, 2010
ISL6263B
VDD


DROOP

VSUM
ESR
DFB
RDRP1
CDRP



CFILTER1
VSEN

RFILTER1
RFILTER2
RTN

RNTC
VO

CN
RDRP2
DROOP

COUT
RS
RNTCP
OCP
ROCSET
ROPN1
OCSET
VDIFF
CFILTER2
CFILTER3
ROPN2


DCR
PHASE
RNTCS
10µA
LOUT
TO
VCC_SNS PROCESSOR
SOCKET
VSS_SNS
KELVIN
CONNECTIONS
FIGURE 5. SIMPLIFIED VOLTAGE DROOP CIRCUIT WITH GPU SOCKET KELVIN SENSING AND INDUCTOR DCR CURRENT SENSING
Smooth mode transitions are facilitated by the R3 modulator
which correctly maintains the internally synthesized ripple
current information throughout mode transitions.
Current Monitor
The ISL6263B features a current monitor output. The
voltage between the IMON and VSS pins is proportional to
the output inductor current. The output inductor current is
proportional to the voltage between the DROOP and VO
pins. The IMON pin has source and sink capability for close
tracking of transient current events. The current monitor
output is expressed in Equation 1:
V IMON =  V DROOP – V O   31
(EQ. 1)
Protection
The ISL6263B 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 levels that are no more than 2.5x the OCP
threshold is 120µs, which is eight counts at 15µs each. The
ISL6263B protects against hard shorts by latching an OCP
fault within 2µs for overcurrent levels exceeding 2.5x the
11
OCP threshold. The value of ROCSET is calculated in
Equation 2:
I OC  R droop
R OCSET = ---------------------------------10.1A
(EQ. 2)
For example: The desired overcurrent trip level, Ioc, is 30A,
Rdroop load-line is 8m, Equation 2 gives ROCSET = 24k.
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
195mV 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
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
FN6388.3
July 8, 2010
ISL6263B
ISL6263B 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
high-side 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.
PWM
LGATE
1V
UGATE
1V
TABLE 3. FAULT PROTECTION SUMMARY OF ISL6263B
FAULT TYPE
FAULT
DURATION
PRIOR TO
PROTECTION
PROTECTION
ACTIONS
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
(+195mV)
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
t PDRU
FAULT
RESET
LGATE, UGATE, and Cycle
PGOOD latched low VR_ON or
VDD
t PDRL
FIGURE 6. GATE DRIVER TIMING DIAGRAM
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
on page 6. 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.
Internal Bootstrap Diode
The ISL6263B 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
1.6
The ISL6263B 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 rDS(ON) MOSFET.
1.4
CBOOT_CAP (µF)
Gate-Driver Outputs LGATE and UGATE
1.2
1.0
0.8
QGATE = 100nC
0.6
nC
50
0.4
0.2
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
VBOOT_CAP (V)
FIGURE 7. BOOTSTRAP CAPACITANCE vs BOOT RIPPLE
VOLTAGE
12
FN6388.3
July 8, 2010
ISL6263B
The minimum value of the bootstrap capacitor can be
calculated using Equation 3:
Q GATE
C BOOT  -----------------------V BOOT
RBIAS Current Reference
(EQ. 3)
where QGATE is the amount of gate charge required to fully
charge the gate of the upper MOSFET. The VBOOT term is
defined as the allowable droop in the rail of the upper drive.
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 ISL6263B 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 on page 7. The value of CSOFT, can be calculated
using Equation 4:
I DVIDmin 180A
C SOFT = ------------------------- = ------------------ = 0.018F
10K
 10mV
----------------
 s 
(EQ. 4)
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 5:
I SS
dV SOFT
42A
2.8mV
----------------------- = ------------------ = -----------------------  -----------------dt
C SOFT 0.015F
s
Note that the slewrate is the average rate of change
between the initial and final voltage values.
13
(EQ. 5)
The RBIAS pin is internally connected to a 1.545V reference
through a 3k resistance. A bias current is established by
connecting a1% tolerance, 150k resistor between the
RBIAS and VSS pins. This bias current is mirrored, creating the
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.
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 approximated by
Equation 6:
–6
 T – 0.5  10 
R FSET = ----------------------------------------– 12
400  10
(EQ. 6)
For example, the value of RFSET for 300kHz operation is
approximately:
–6
–6
 3.33  10 – 0.5  10 
3
7.1 10 = -------------------------------------------------------------------– 12
400  10
(EQ. 7)
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.
Static Droop Design Using DCR Sensing
The ISL6263B 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
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 8 gives this relationship
V DCR = I o  DCR
(EQ. 8)
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.
FN6388.3
July 8, 2010
ISL6263B
where G1target is the desired ratio of Vn / VDCR. Therefore,
the temperature characteristics G1 is described by
Equation 14:
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 0.3 to 0.8 times VDCR. This gain,
defined as G1, provides a reasonable amount of light load
signal from which to derive the droop voltage.
G 1t arg et
G 1  T  = -------------------------------------------------------------------- 1 + 0.00393   T – 25C  
It is recommended to begin your droop design using the
RNTC, RNTCS, and RNTCP component values of the
evaluation board available from Intersil.
The NTC network resistor value is dependent on
temperature and is given by Equation 9:
 R NTC + R NTCS   R NTCP
R N  T  = -----------------------------------------------------------------------R NTC + R NTCS + R NTCP
The gain of the droop amplifier circuit is expressed in
Equation 15:
(EQ. 9)
R DRP2
k droopamp = 1 + ------------------R DRP1
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. 15)
After determining RS and RNTCEQ networks, use
Equation 16 to calculate the droop resistances RDRP1 and
RDRP2.
(EQ. 10)
The inductor DCR is a function of temperature and is
approximately given by Equation 11:
DCR  T  = DCR 25C   1 + 0.00393   T – 25C  
(EQ. 14)
R droop



R DRP2 =   ------------------------------------------- – 1  R DRP1
DCR

G


1  25C 
(EQ. 11)
(EQ. 16)
The droop amplifier output voltage divided by the total load
current is given by Equation 12:
Rdroop is 8m per Intel IMVP-6+ specification and RDRP1 is
typically 1k.
R droop = G 1  T   DCR 25C   1 + 0.00393   T – 25C    k droopamp
(EQ. 12)
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.
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:
G 1  T    1 + 0.00393   T – 25C    G 1t arg et
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.
(EQ. 13)
VDD

OCSET

RS
VSUM
DFB
DROOP
VO
VDCR
RDRP1


DROOP

RNTCEQ

CN

OCP
ROCSET
RDRP2
10A
FIGURE 8. EQUIVALENT MODEL FOR DROOP CIRCUIT USING INDUCTOR DCR CURRENT SENSING
14
FN6388.3
July 8, 2010
ISL6263B
VDD

OCSET
OCP

RS
VSUM

DROOP


ROCSET
DFB
DROOP
VO
VRSNS
RDRP1

CN

RDRP2
10A
FIGURE 9. EQUIVALENT MODEL FOR DROOP CIRCUIT USING DISCRETE RESISTOR CURRENT SENSING
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 17:
160mV
R DRP2new = -------------------   R DRP1 + R DRP2  – R DRP1
155mV
Icore
Vcore
Vcore
Vcore= IcoreRdroop
FIGURE 10. DESIRED LOAD TRANSIENT RESPONSE
WAVEFORMS
(EQ. 17)
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.
15
Vcore
icore
icore
Vcore
Vcore
FIGURE 11. LOAD TRANSIENT RESPONSE WHEN CN IS TOO
SMALL
icore
Vcore
Vcore
FIGURE 12. LOAD TRANSIENT RESPONSE WHEN CN IS TOO
LARGE
FN6388.3
July 8, 2010
ISL6263B
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 18 shows this relationship:
 R NTCEQ  R S 
L
-  C N
------------- =  -------------------------------------DCR
 R NTCEQ + R S
(EQ. 18)
Equation 22 shows the droop amplifier gain. So the actual
droop is given by:
R DRP2

R droop = R SNS   1 + -------------------
R DRP1

(EQ. 22)
Solution to RDRP2 yields Equation 23 :
 R droop

R DRP2 = R DRP1   ------------------- – 1
 R SNS

(EQ. 23)
For example: Rdroop = 8.0m, RSNS = 1.0m, and
RDRP1 = 1k, RDRP2 then = 7k
Solution of CN yields:
L 
 ------------ DCR
C N = ------------------------------------------- R NTCEQ  R S 
 ---------------------------------------
 R NTCEQ + R S
(EQ. 19)
For example: L = 0.45µH, DCR = 1.1m, RS = 7.68k, and
RNTCEQ = 3.4k
 0.45H
--------------------
 1.1m 
C N = ------------------------------------------------- = 174nF
3.4k  7.68k 
 ----------------------------------------- 3.4k + 7.68k
Dynamic Mode of Operation - Compensation
Parameters
(EQ. 20)
Since the inductance and the DCR typically have 20% and
7% tolerance respectively, CN needs to be fine tuned on the
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
high-grade 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 100
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 21:
V RSNS = I o  R SNS
(EQ. 21)
16
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.
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 8.0m 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 8.0m. Intersil provides a spreadsheet to
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 3k.
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
ISL6263B 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.
FN6388.3
July 8, 2010
ISL6263B
LGATE, PVCC, and PGND
RBIAS
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.
The resistor RRBIAS should be placed in close proximity to
the ISL6263B using a noise-free current return path to the
VSS pin.
VIAS TO
GROUND
PLANE
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.
GND
OUTPUT
CAPACITORS
SCHOTTKY
DIODE
VOUT
INDUCTOR
IMON, SOFT, OCSET, V W, COMP, FB, VDIFF,
DROOP, DFB, VO, and VSUM
PHASE
NODE
HIGH-SIDE
MOSFETS
LOW-SIDE
MOSFETS
INPUT
CAPACITORS
VIN
FIGURE 13. TYPICAL POWER COMPONENT PLACEMENT
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.
VSEN and RTN
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 10 to avoid
interaction with the 50k 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
Resistor RS is preferably located near the boundary
between the power ground and the island of analog ground
connected 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 ISO9001 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
17
FN6388.3
July 8, 2010
ISL6263B
Package Outline Drawing
L32.5x5
32 LEAD QUAD FLAT NO-LEAD PLASTIC PACKAGE
Rev 2, 02/07
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 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 indentifier may be
either a mold or mark feature.
18
FN6388.3
July 8, 2010
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