ISL6326B [INTERSIL]
4-Phase PWM Controller with 8-Bit DAC Code Capable of Precision DCR Differential Current Sensing; 4相PWM控制器,带有8位DAC代码,能够高精度差分DCR电流检测的型号: | ISL6326B |
厂家: | Intersil |
描述: | 4-Phase PWM Controller with 8-Bit DAC Code Capable of Precision DCR Differential Current Sensing |
文件: | 总30页 (文件大小:549K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
ISL6326B
®
Data Sheet
April 21, 2006
FN9286.0
4-Phase PWM Controller with 8-Bit DAC
Code Capable of Precision DCR
Differential Current Sensing
Features
• Proprietary Active Pulse Positioning and Adaptive Phase
Alignment Modulation Scheme
The ISL6326B controls microprocessor core voltage
regulation by driving up to 4 synchronous-rectified buck
channels in parallel. Multiphase buck converter architecture
uses interleaved timing to multiply channel ripple frequency
and reduce input and output ripple currents. Lower ripple
results in fewer components, lower component cost, reduced
power dissipation, and smaller implementation area.
• Precision Multiphase Core Voltage Regulation
- Differential Remote Voltage Sensing
- ±0.5% System Accuracy Over Life, Load, Line and
Temperature
- Adjustable Precision Reference-Voltage Offset
• Precision resistor or DCR Current Sensing
- Accurate Load-Line Programming
- Accurate Channel-Current Balancing
- Differential Current Sense
Microprocessor loads can generate load transients with
extremely fast edge rates. The ISL6326B utilizes Intersil’s
proprietary Active Pulse Positioning (APP) and Adaptive
Phase Alignment (APA) modulation scheme to achieve the
extremely fast transient response with fewer output
capacitors.
• Microprocessor Voltage Identification Input
- Dynamic VID™ Technology
- 8-Bit VID Input with Selectable VR11 Code and
Extended VR10 Code at 6.25mV Per Bit
Today’s microprocessors require a tightly regulated output
voltage position versus load current (droop). The ISL6326B
senses the output current continuously by utilizing patented
techniques to measure the voltage across the dedicated
current sense resistor or the DCR of the output inductor. The
sensed current flows out of FB pin to develop the precision
voltage drop across the feedback resistor for droop control.
Current sensing also provides the needed signals for
channel-current balancing, and overcurrent protection. A
programmable integrated temperature compensation
function is implemented to effectively compensate for the
temperature coefficient of the current sense element. The
current limit function provides the overcurrent protection for
the individual phase.
• Thermal Monitoring
• Integrated Programmable Temperature Compensation
• Overcurrent Protection and Channel Current Limit
• Load Current Indicator and External Overcurrent
Protection Threshold Setup
• Overvoltage Protection
• 2, 3 or 4 Phase Operation
• Adjustable Switching Frequency up to 1MHz Per Phase
• Package Option
- QFN Compliant to JEDEC PUB95 MO-220 QFN - Quad
Flat No Leads - Product Outline
A unity gain, differential amplifier is provided for remote
voltage sensing. Any potential difference between remote
and local grounds can be completely eliminated using the
remote-sense amplifier. Eliminating ground differences
improves regulation and protection accuracy. The threshold-
sensitive enable input is available to accurately coordinate
the start up of the ISL6326B with any other voltage rail.
Dynamic-VID™ technology allows seamless on-the-fly VID
changes. The offset pin allows accurate voltage offset
settings that are independent of VID setting.
- QFN Near Chip Scale Package Footprint; Improves
PCB Efficiency, Thinner in Profile
• Pb-Free Plus Anneal Available (RoHS Compliant)
Ordering Information
PART
NUMBER
(Note)
PART
MARKING
TEMP.
(°C)
PACKAGE
(Pb-Free)
PKG.
DWG. #
ISL6326BCRZ ISL6326BCRZ 0 to70 40 Ld 6x6 QFN L40.6x6
ISL6326BIRZ ISL6326BIRZ -40 to 85 40 Ld 6x6 QFN L40.6x6
Add “-T” suffix for tape and reel.
NOTE: Intersil Pb-free plus anneal products employ special Pb-free
material sets; molding compounds/die attach materials and 100%
matte tin plate termination finish, which are 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.
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2006. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
ISL6326B
Pinout
ISL6326B (40 LD QFN)
TOP VIEW
40 39 38 37 36 35 34 33 32 31
VID6
VID5
VID4
VID3
VID2
VID1
VID0
VRSEL
OFS
ISEN3+
ISEN3-
ISEN2-
ISEN2+
PWM2
PWM4
ISEN4+
ISEN4-
ISEN1-
ISEN1+
1
2
30
29
28
27
26
25
24
23
22
21
3
4
5
GND
6
7
8
9
DAC
10
11 12 13 14 15 16 17 18 19 20
FN9286.0
April 21, 2006
2
ISL6326B
ISL6326BCR Block Diagram
VDIFF VR_RDY
FS
0.875
0.875
-
CLOCK AND
RAMP GENERATOR
POWER-ON
RESET (POR)
RGND
VSEN
-
+
X1
EN_VTT
+
N
-
+
EN_PWR
SOFTSTART
AND
+
OVP
-
FAULT LOGIC
+175mV
APP and APA
MODULATOR
PWM1
PWM2
SS
VRSEL
APP and APA
MODULATOR
VID7
VID6
VID5
VID4
VID3
VID2
VID1
VID0
Dynamic
VID
D/A
APP and APA
MODULATOR
PWM3
PWM4
DAC
OFS
APP and APA
MODULATOR
OFFSET
+
REF
FB
CHANNEL
CURRENT
BALANCE
CHANNEL
DETECT
E/A
-
AND PEAK
CURRENT LIMIT
COMP
N
ISEN1+
ISEN1-
ISEN2+
ISEN2-
ISEN3+
ISEN3-
ISEN4+
ISEN4-
I_TRIP
2.0V
-
+
-
+
OCP
OCP
CHANNEL
CURRENT
SENSE
TEMPERATURE
COMPENSATION
1
N
IOUT
Σ
VR_HOT
VR_FAN
TEMPERATURE
COMPENSATION
GAIN ADJUST
THERMAL
MONITOR
TM
TCOMP
GND
FN9286.0
April 21, 2006
3
ISL6326B
Typical Application - 4-Phase Buck Converter with Integrated Thermal Compensation
VIN
VIN
VIN
VIN
+12V
PVCC
BOOT
+5V
VCC
UGATE
PHASE
ISL6612
DRIVER
LGATE
GND
PWM
COMP VCC DAC
REF
FB
VDIFF
VSEN
PWM1
ISEN1-
ISEN1+
+12V
RGND
EN_VTT
BOOT
PVCC
VTT
VR_RDY
VID7
VCC
UGATE
PHASE
ISL6326B
VID6
ISL6612
DRIVER
VID5
LGATE
GND
VID4
PWM
PWM2
VID3
VID2
ISEN2-
ISEN2+
VID1
VID0
+12V
VRSEL
VR_FAN
VR_HOT
BOOT
PVCC
PWM3
ISEN3-
uP
LOAD
VCC
UGATE
PHASE
ISEN3+
VIN
ISL6612
DRIVER
EN_PWR
LGATE
GND
PWM
GND
IOUT
PWM4
ISEN4-
ISEN4+
TCOMP
TM
+12V
BOOT
OFS
FS
SS
PVCC
+5V
+5V
VCC
UGATE
PHASE
ISL6612
DRIVER
NTC
LGATE
GND
PWM
FN9286.0
April 21, 2006
4
ISL6326B
Typical Application - 4-Phase Buck Converter with External Thermal Compensation
NTC
+12V
+5V
oC
VIN
BOOT1
VCC
UGATE1
PHASE1
COMP VCC DAC
REF
FB
GND
LGATE1
VDIFF
VSEN
5V
To
12V
PVCC
ISL6614
DRIVER
VIN
RGND
EN_VTT
BOOT2
ISEN1+
ISEN1-
VTT
VR_RDY
VID7
PWM1
PWM2
UGATE2
PHASE2
PWM1
VID6
VID5
ISL6326B
LGATE2
PGND
VID4
VID3
PWM3
VID2
ISEN3-
ISEN3+
VID1
VID0
VRSEL
VR_FAN
VR_HOT
ISEN2+
ISEN2-
uP
LOAD
+12V
VIN
PWM2
BOOT1
VCC
VIN
UGATE1
PHASE1
EN_PWR
GND
PWM4
GND
ISEN4-
ISEN4+
LGATE1
IOUT
5V
To
12V
PVCC
ISL6614
DRIVER
TCOMP
TM
VIN
BOOT2
OFS
FS
SS
+5V
PWM1
PWM2
UGATE2
PHASE2
NTC
LGATE2
PGND
FN9286.0
April 21, 2006
5
ISL6326B
Absolute Maximum Ratings
Thermal Information
Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+6V
All Pins. . . . . . . . . . . . . . . . . . . . . . . . . . . GND -0.3V to V + 0.3V
Thermal Resistance (Notes 1, 2)
θ
(°C/W)
θ
(°C/W)
JA
JC
CC
QFN Package. . . . . . . . . . . . . . . . . . . .
32
3.5
ESD (Human Body Model). . . . . . . . . . . . . . . . . . . . . . . . . . . . .>2kV
ESD (Machine Model) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .>200V
ESD (Charged Device Model) . . . . . . . . . . . . . . . . . . . . . . . . >1.5kV
Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . 150°C
Maximum Storage Temperature Range. . . . . . . . . . .-65°C to 150°C
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . . 300°C
Operating Conditions
Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . +5V ±5%
Ambient Temperature (ISL6326BCRZ) . . . . . . . . . . . . . 0°C to 70°C
Ambient Temperature (ISL6326BIRZ) . . . . . . . . . . . . .-40°C to 85°C
CAUTION: Stress above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational section of this specification is not implied.
NOTES:
1. θ is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See
JA
Tech Brief TB379
2. For θ , the “case temp” location is the center of the exposed metal pad on the package underside.
JC
Electrical Specifications Operating Conditions: VCC = 5V, Unless Otherwise Specified
PARAMETER
VCC SUPPLY CURRENT
Nominal Supply
TEST CONDITIONS
MIN
TYP MAX UNITS
VCC = 5VDC; EN_PWR = 5VDC; R = 100kΩ,
-
-
18
14
26
21
mA
mA
T
ISEN1 = ISEN2 = ISEN3 = ISEN4 = -70μA
Shutdown Supply
VCC = 5VDC; EN_PWR = 0VDC; R = 100kΩ
T
POWER-ON RESET AND ENABLE
POR Threshold
VCC Rising
VCC Falling
Rising
4.3
3.7
4.5
3.9
4.7
4.2
V
V
EN_PWR Threshold
EN_VTT Threshold
0.850 0.875 0.910
130
V
Hysteresis
Falling
-
-
mV
V
0.720 0.745 0.775
0.850 0.875 0.910
Rising
V
Hysteresis
Falling
-
130
-
mV
V
0.720 0.745 0.775
REFERENCE VOLTAGE AND DAC
System Accuracy of ISL6326BCRZ
(VID = 1V-1.6V, T = 0°C to 70°C)
J
(Note 3)
(Note 3)
(Note 3)
(Note 3)
-0.5
-0.9
-0.6
-1
-
-
-
-
0.5
0.9
0.6
1
%VID
%VID
%VID
%VID
System Accuracy of ISL6326BCRZ
(VID = 0.5V-1V, T = 0°C to 70°C)
J
System Accuracy of ISL6326BIRZ
(VID = 1V-1.6V, T = -40°C to 85°C)
J
System Accuracy of ISL6326BIRZ
(VID = 0.5V-1V, T = -40°C to 85°C)
J
VID Pull Up
-60
-
-40
-20
0.4
-
µA
V
VID Input Low Level
VID Input High Level
VRSEL Input Low Level
VRSEL Input High Level
DAC Source Current
-
-
0.8
-
V
-
0.4
-
V
0.8
-
-
V
4
7
mA
FN9286.0
April 21, 2006
6
ISL6326B
Electrical Specifications Operating Conditions: VCC = 5V, Unless Otherwise Specified (Continued)
PARAMETER
DAC Sink Current
TEST CONDITIONS
MIN
-
TYP MAX UNITS
-
300
55
µA
µA
µA
REF Source Current
REF Sink Current
45
45
50
50
55
PIN-ADJUSTABLE OFFSET
Voltage at OFS Pin
Offset resistor connected to ground
Voltage below VCC, offset resistor connected to VCC
380
400
420
mV
V
1.55
1.60
1.65
OSCILLATORS
Accuracy of Switching Frequency Setting
R
= 100kΩ
225
0.08
-
250
275
1.0
-
kHz
MHz
T
Adjustment Range of Switching Frequency (Note 4)
Soft-start Ramp Rate = 100kΩ (Notes 5, 6)
-
1.563
-
R
mV/µs
S
Adjustment Range of Soft-Start Ramp Rate (Note 4)
PWM GENERATOR
0.625
6.25 mV/µs
Sawtooth Amplitude
-
1.25
-
V
ERROR AMPLIFIER
Open-Loop Gain
R
= 10kΩ to ground (Note 4)
-
-
96
80
25
4.3
-
-
-
dB
MHz
V/µs
V
L
Open-Loop Bandwidth
Slew Rate
(Note 4)
(Note 4)
-
-
Maximum Output Voltage
Output High Voltage @ 2mA
Output Low Voltage @ 2mA
REMOTE-SENSE AMPLIFIER
Bandwidth
3.8
3.6
-
4.9
-
V
-
1.8
V
(Note 4)
-
20
-
-
MHz
µA
Output High Current
VSEN - RGND = 2.5V
VSEN - RGND = 0.6
-500
-500
500
500
Output High Current
-
µA
PWM OUTPUT
PWM Output Voltage LOW Threshold
PWM Output Voltage HIGH Threshold
Iload = ±500μA
Iload = ±500μA
-
-
-
0.5
-
V
V
4.3
CURRENT SENSE AND OVERCURRENT PROTECTION
Sensed Current Tolerance (IOUT)
ISEN1 = ISEN2 = ISEN3 = ISEN4 = 60μA
57
72
60
85
63
98
µA
µA
µA
V
Overcurrent Trip Level for Average Current
Peak Current Limit for Individual Channel
IOUT Trip Level for Overcurrent protection
THERMAL MONITORING AND FAN CONTROL
TM Input Voltage for VR_FAN Trip
100
1.85
120
2.0
140
2.15
1.55
1.85
1.30
1.55
-
1.65
1.95
1.40
1.65
-
1.75
2.05
1.50
1.75
30
V
V
TM Input Voltage for VR_FAN Reset
TM Input Voltage for VR_HOT Trip
V
TM Input Voltage for VR_HOT Reset
V
Leakage Current of VR_FAN
VR_FAN Low Voltage
With externally pull-up resistor connected to VCC
With 1.25k resistor pull-up to VCC, I = 4mA
µA
V
-
-
0.4
VR_FAN
FN9286.0
April 21, 2006
7
ISL6326B
Electrical Specifications Operating Conditions: VCC = 5V, Unless Otherwise Specified (Continued)
PARAMETER
Leakage Current of VR_HOT
VR_HOT Low Voltage
TEST CONDITIONS
MIN
TYP MAX UNITS
With externally pull-up resistor connected to VCC
-
-
-
-
30
µA
V
With 1.25k resistor pull-up to VCC, I
= 4mA
0.4
VR_HOT
VR READY AND PROTECTION MONITORS
Leakage Current of VR_RDY
With externally pull-up resistor connected to VCC
= 4mA
-
-
30
0.4
52
62
μA
V
VR_RDY Low Voltage
I
-
-
VR_RDY
Undervoltage Threshold
VR_RDY Reset Voltage
Overvoltage Protection Threshold
VDIFF Falling
48
58
50
60
%VID
%VID
V
VDIFF Rising
Before valid VID
1.250 1.275 1.300
After valid VID, the voltage above VID
150
-
175
100
200
-
mV
mV
Overvoltage Protection Reset Hysteresis
NOTES:
3. These parts are designed and adjusted for accuracy with all errors in the voltage loop included.
4. Spec guaranteed by design.
5. During soft-start, VDAC rises from 0 to 1.1V first and then ramp to VID voltage after receiving valid VID.
6. Soft-start ramp rate is determined by the adjustable soft-start oscillator frequency at the speed of 6.25mV per cycle.
FN9286.0
April 21, 2006
8
ISL6326B
the amplifier’s output and the input to the regulation and
protection circuitry. Connect VSEN and RGND to the sense
pins of the remote load.
Functional Pin Description
VCC - Supplies the power necessary to operate the chip.
The controller starts to operate when the voltage on this pin
exceeds the rising POR threshold and shuts down when the
voltage on this pin drops below the falling POR threshold.
Connect this pin directly to a +5V supply.
FB and COMP - Inverting input and output of the error
amplifier respectively. FB can be connected to VDIFF
through a resistor. A properly chosen resistor between
VDIFF and FB can set the load line (droop), because the
sensed current will flow out of FB pin. The droop scale factor
is set by the ratio of the ISEN resistors and the inductor DCR
or the dedicated current sense resistor. COMP is tied back to
FB through an external R-C network to compensate the
regulator.
GND - Bias and reference ground for the IC. The bottom
metal base of ISL6326B is the GND.
EN_PWR - This pin is a threshold-sensitive enable input for
the controller. Connecting the 12V supply to EN_PWR
through an appropriate resistor divider provides a means to
synchronize power-up of the controller and the MOSFET
driver ICs. When EN_PWR is driven above 0.875V, the
ISL6326B is active depending on status of EN_VTT, the
internal POR, and pending fault states. Driving EN_PWR
below 0.745V will clear all fault states and prime the
ISL6326B to soft-start when re-enabled.
DAC and REF - The DAC pin is the output of the precision
internal DAC reference. The REF pin is the positive input of
the Error Amp. In typical applications, a 1kΩ, 1% resistor is
used between DAC and REF to generate a precision offset
voltage. This voltage is proportional to the offset current
determined by the offset resistor from OFS to ground or
VCC. A capacitor is used between REF and ground to
smooth the voltage transition during Dynamic VID™
operations.
EN_VTT - This pin is another threshold-sensitive enable
input for the controller. It’s typically connected to VTT output
of VTT voltage regulator in the computer mother board.
When EN_VTT is driven above 0.875V, the ISL6326B is
active depending on status of EN_PWR, the internal POR,
and pending fault states. Driving EN_VTT below 0.745V will
clear all fault states and prime the ISL6326B to soft-start
when re-enabled.
PWM1, PWM2, PWM3, PWM4 - Pulse width modulation
outputs. Connect these pins to the PWM input pins of the
Intersil driver IC. The number of active channels is
determined by the state of PWM3 and PWM4. Tie PWM3 to
VCC to configure for 2-phase operation. Tie PWM4 to VCC
to configure for 3-phase operation.
FS - Use this pin to set up the desired switching frequency. A
resistor, placed from FS to ground will set the switching
frequency. The relationship between the value of the resistor
and the switching frequency will be described by an
approximate equation.
ISEN1+, ISEN1-; ISEN2+, ISEN2-; ISEN3+, ISEN3-;
ISEN4+, ISEN4- - The ISEN+ and ISEN- pins are current
sense inputs to individual differential amplifiers. The sensed
current is used for channel current balancing, overcurrent
protection, and droop regulation. Inactive channels should
have their respective current sense inputs left open (for
example, open ISEN4+ and ISEN4- for 3-phase operation).
SS - Use this pin to set up the desired start-up oscillator
frequency. A resistor, placed from SS to ground will set up
the soft-start ramp rate. The relationship between the value
of the resistor and the soft-start ramp up time will be
described by an approximate equation.
For DCR sensing, connect each ISEN- pin to the node
between the RC sense elements. Tie the ISEN+ pin to the
VID7, VID6, VID5, VID4, VID3, VID2, VID1 and VID0 -
These are the inputs to the internal DAC that generates the
reference voltage for output regulation. Connect these pins
either to open-drain outputs with or without external pull-up
resistors or to active-pull-up outputs. All VID pins have 40µA
internal pull-up current sources that diminish to zero as the
voltage rises above the logic-high level. These inputs can be
pulled up externally as high as VCC plus 0.3V.
other end of the sense capacitor through a resistor, R .
ISEN
The voltage across the sense capacitor is proportional to the
inductor current. Therefore, the sense current is proportional
to the inductor current, and scaled by the DCR of the
inductor and R
.
ISEN
To match the time delay of the internal circuit, a capacitor is
needed between each ISEN+ pin and GND, as described in
the Current Sensing section.
VRSEL - use this pin to select internal VID code. When it is
connected to GND, the extended VR10 code is selected.
When it’s floated or pulled to high, VR11 code is selected.
This input can be pulled up as high as VCC plus 0.3V.
VR_RDY - VR_RDY indicates that soft-start has completed
and the output voltage is within the regulated range around
VID setting. It is an open-drain logic output. When OCP or
OVP occurs, VR_RDY will be pulled to low. It will also be
pulled low if the output voltage is below the under-voltage
threshold.
VDIFF, VSEN, and RGND - VSEN and RGND form the
precision differential remote-sense amplifier. This amplifier
converts the differential voltage of the remote output to a
single-ended voltage referenced to local ground. VDIFF is
FN9286.0
April 21, 2006
9
ISL6326B
OFS - The OFS pin can be used to program a DC offset
Operation
current which will generate a DC offset voltage between the
REF and DAC pins. The offset current is generated via an
external resistor and precision internal voltage references.
The polarity of the offset is selected by connecting the
resistor to GND or VCC. For no offset, the OFS pin should
be left unterminated.
Multiphase Power Conversion
Microprocessor load current profiles have changed to the
point that the advantages of multiphase power conversion
are impossible to ignore. The technical challenges
associated with producing a single-phase converter which is
both cost-effective and thermally viable have forced a
change to the cost-saving approach of multiphase. The
ISL6326B controller helps reduce the complexity of
implementation by integrating vital functions and requiring
minimal output components. The block diagrams on pages
3, 4, and 5 provide top level views of multiphase power
conversion using the ISL6326B controller.
TCOMP - Temperature compensation scaling input. The
voltage sensed on the TM pin is utilized as the temperature
input to adjust ldroop and the overcurrent protection limit to
effectively compensate for the temperature coefficient of the
current sense element. To implement the integrated
temperature compensation, a resistor divider circuit is
needed with one resistor being connected from TCOMP to
VCC of the controller and another resistor being connected
from TCOMP to GND. Changing the ratio of the resistor
values will set the gain of the integrated thermal
Interleaving
The switching of each channel in a multiphase converter is
timed to be symmetrically out of phase with each of the other
channels. In a 3-phase converter, each channel switches 1/3
cycle after the previous channel and 1/3 cycle before the
following channel. As a result, the three-phase converter has
a combined ripple frequency three times greater than the
ripple frequency of any one phase. In addition, the peak-to-
peak amplitude of the combined inductor currents is reduced
in proportion to the number of phases (Equations 1 and 2).
Increased ripple frequency and lower ripple amplitude mean
that the designer can use less per-channel inductance and
lower total output capacitance for any performance
specification.
compensation. When integrated temperature compensation
function is not used, connect TCOMP to GND.
IOUT - IOUT is the output pin of sensed average channel
current. In actual application, a resistor needs to be placed
between IOUT and GND to ensure the proper operation. The
voltage at IOUT pin will be proportional to the load current
and the resistor value. ISL6326B monitors the voltage at
IOUT for overcurrent protection. If the voltage at IOUT pin is
higher than 2V, it will trigger the overcurrent shutdown. By
choosing the proper value for the resistor at IOUT pin, the
overcurrent trip level can be set to be lower than the fixed
internal overcurrent threshold. Tie it to GND if not used.
Figure 1 illustrates the multiplicative effect on output ripple
frequency. The three channel currents (IL1, IL2, and IL3)
combine to form the AC ripple current and the DC load
current. The ripple component has three times the ripple
frequency of each individual channel current. Each PWM
pulse is terminated 1/3 of a cycle after the PWM pulse of the
previous phase. The DC components of the inductor currents
combine to feed the load.
TM - TM is an input pin for the VR temperature
measurement. Connect this pin through an NTC thermistor
to GND and a resistor to VCC of the controller. The voltage
at this pin is reverse proportional to the VR temperature.
ISL6326B monitors the VR temperature based on the
voltage at the TM pin and outputs VR_HOT and VR_FAN
signals.
VR_HOT - VR_HOT is used as an indication of high VR
temperature. It is an open-drain logic output. It will be pulled
low if the measured VR temperature is less than a certain
level, and open when the measured VR temperature
reaches a certain level. A external pull-up resistor is needed.
IL1 + IL2 + IL3, 7A/DIV
IL1, 7A/DIV
VR_FAN - VR_FAN is an output pin with open-drain logic
output. It will be pulled low if the measured VR temperature
is less than a certain level, and open when the measured VR
temperature reaches a certain level. A external pull-up
resistor is needed.
PWM1, 5V/DIV
IL2, 7A/DIV
PWM2, 5V/DIV
IL3, 7A/DIV
PWM3, 5V/DIV
1µs/DIV
FIGURE 1. PWM AND INDUCTOR-CURRENT WAVEFORMS
FOR 3-PHASE CONVERTER
FN9286.0
April 21, 2006
10
ISL6326B
To understand the reduction of ripple current amplitude in the
multiphase circuit, examine the equation representing an
individual channel’s peak-to-peak inductor current.
RMS input capacitor current. The single-phase converter
must use an input capacitor bank with twice the RMS current
capacity as the equivalent three-phase converter.
(V – V
) V
OUT
Figures 17, 18 and 19 in the section entitled Input Capacitor
Selection can be used to determine the input-capacitor RMS
current based on load current, duty cycle, and the number of
channels. They are provided as aids in determining the
optimal input capacitor solution. Figure 20 shows the single
phase input-capacitor RMS current for comparison.
IN
OUT
(EQ. 1)
I
= -----------------------------------------------------
PP
Lf
V
S
IN
In Equation 1, V and V
IN
are the input and output
OUT
voltages respectively, L is the single-channel inductor value,
and f is the switching frequency.
S
PWM Modulation Scheme
INPUT-CAPACITOR CURRENT, 10A/DIV
The ISL6326B adopts Intersil's proprietary Active Pulse
Positioning (APP) modulation scheme to improve transient
performance. APP control is a unique dual-edge PWM
modulation scheme with both PWM leading and trailing
edges being independently moved to give the best response
to transient loads. The PWM frequency, however, is constant
and set by the external resistor between the FS pin and
GND. To further improve the transient response, the
ISL6326B also implements Intersil's proprietary Adaptive
Phase Alignment (APA) technique. APA, with sufficiently
large load step currents, can turn on all phases together.
With both APP and APA control, ISL6326B can achieve
excellent transient performance and reduce the demand on
the output capacitors.
CHANNEL 1
INPUT CURRENT
10A/DIV
CHANNEL 2
INPUT CURRENT
10A/DIV
CHANNEL 3
INPUT CURRENT
10A/DIV
1µs/DIV
FIGURE 2. CHANNEL INPUT CURRENTS AND INPUT-
CAPACITOR RMS CURRENT FOR 3-PHASE
CONVERTER
Under steady state conditions the operation of the ISL6326B
PWM modulator appears to be that of a conventional trailing
edge modulator. Conventional analysis and design methods
can therefore be used for steady state and small signal
operation.
The output capacitors conduct the ripple component of the
inductor current. In the case of multiphase converters, the
capacitor current is the sum of the ripple currents from each
of the individual channels. Compare Equation 1 to the
expression for the peak-to-peak current after the summation
of N symmetrically phase-shifted inductor currents in
Equation 2. Peak-to-peak ripple current decreases by an
amount proportional to the number of channels. Output-
voltage ripple is a function of capacitance, capacitor
equivalent series resistance (ESR), and inductor ripple
current. Reducing the inductor ripple current allows the
designer to use fewer or less costly output capacitors.
PWM Operation
The timing of each channel is set by the number of active
channels. The default channel setting for the ISL6326B is
four. The switching cycle is defined as the time between
PWM pulse termination signals of each channel. The cycle
time of the pulse signal is the inverse of the switching
frequency set by the resistor between the FS pin and
ground. The PWM signals command the MOSFET driver to
turn on/off the channel MOSFETs.
(V – N V
) V
OUT
For 4-channel operation, the channel firing order is 4-3-2-1:
PWM3 pulse happens 1/4 of a cycle after PWM4, PWM2
output follows another 1/4 of a cycle after PWM3, and
PWM1 delays another 1/4 of a cycle after PWM2. For
3-channel operation, the channel firing order is 3-2-1.
IN
OUT
I
= -----------------------------------------------------------
(EQ. 2)
C, PP
Lf
V
S
IN
Another benefit of interleaving is to reduce input ripple
current. Input capacitance is determined in part by the
maximum input ripple current. Multiphase topologies can
improve overall system cost and size by lowering input ripple
current and allowing the designer to reduce the cost of input
capacitance. The example in Figure 2 illustrates input
currents from a three-phase converter combining to reduce
the total input ripple current.
Connecting PWM4 to VCC selects three channel operation
and the pulse times are spaced in 1/3 cycle increments. If
PWM3 is connected to VCC, two channel operation is
selected and the PWM2 pulse happens 1/2 of a cycle after
PWM pulse.
Switching Frequency
The converter depicted in Figure 2 delivers 36A to a 1.5V load
from a 12V input. The RMS input capacitor current is 5.9A.
Compare this to a single-phase converter also stepping down
12V to 1.5V at 36A. The single-phase converter has 11.9A
Switching frequency is determined by the selection of the
frequency-setting resistor, R , which is connected from FS
pin to GND (see the figures labelled Typical Applications on
T
FN9286.0
April 21, 2006
11
ISL6326B
pages 4 and 5). Equation 3 is provided to assist in selecting
the correct resistor value.
V
IN
I
(s)
L
10
L
2.5X10
DCR
V
OUT
R
= -------------------------
(EQ. 3)
T
F
ISL6605
SW
INDUCTOR
-
C
OUT
V
L
where F
is the switching frequency of each phase.
SW
-
(s)
V
C
Current Sensing
R
C
ISL6326B senses the current continuously for fast response.
ISL6326B supports inductor DCR sensing, or resistive
sensing techniques. The associated channel current sense
amplifier uses the ISEN inputs to reproduce a signal
PWM(n)
ISL6326B INTERNAL CIRCUIT
R
ISEN(n)
(PTC)
proportional to the inductor current, I . The sense current,
L
I
n
I
, is proportional to the inductor current. The sensed
SEN
current is used for current balance, load-line regulation, and
overcurrent protection.
CURRENT
SENSE
ISEN-(n)
+
-
The internal circuitry, shown in Figures 3, and 4, represents
one channel of an N-channel converter. This circuitry is
repeated for each channel in the converter, but may not be
active depending on the status of the PWM3 and PWM4
pins, as described in the PWM Operation section.
ISEN+(n)
C
T
DCR
I
-----------------
= I
SEN
L
R
ISEN
INDUCTOR DCR SENSING
An inductor’s winding is characteristic of a distributed
resistance as measured by the DCR (Direct Current
Resistance) parameter. Consider the inductor DCR as a
separate lumped quantity, as shown in Figure 3. The
FIGURE 3. DCR SENSING CONFIGURATION
With the internal low-offset current amplifier, the capacitor
voltage V is replicated across the sense resistor R
.
C
ISEN
, is proportional
channel current I , flowing through the inductor, will also
L
Therefore, the current out of ISEN+ pin, I
to the inductor current.
SEN
pass through the DCR. Equation 4 shows the s-domain
equivalent voltage across the inductor V .
L
Because of the internal filter at ISEN- pin, one capacitor, C ,
T
is needed to match the time delay between the ISEN- and
V
= I ⋅ (s ⋅ L + DCR)
L
(EQ. 4)
L
ISEN+ signals. Select the proper C to keep the time
T
constant of R
and C (R x C ) close to 27ns.
ISEN T
A simple R-C network across the inductor extracts the DCR
voltage, as shown in Figure 3.
ISEN
T
Equation 6 shows that the ratio of the channel current to the
sensed current, I , is driven by the value of the sense
resistor and the DCR of the inductor.
The voltage on the capacitor V , can be shown to be
C
SEN
proportional to the channel current I , see Equation 5.
L
L
DCR
⎛
⎝
⎞
-------------
s ⋅
+ 1 ⋅ (DCR ⋅ I )
-----------------
I
= I
⋅
(EQ. 6)
L
⎠
(EQ. 5)
SEN
L
DCR
R
ISEN
V
= --------------------------------------------------------------------
C
(s ⋅ RC + 1)
RESISTIVE SENSING
For accurate current sense, a dedicated current-sense
resistor R in series with each output inductor can
If the R-C network components are selected such that the
RC time constant (= R*C) matches the inductor time
constant (= L/DCR), the voltage across the capacitor V is
SENSE
C
serve as the current sense element (see Figure 4). This
technique is more accurate, but reduces overall converter
efficiency due to the additional power loss on the current
equal to the voltage drop across the DCR, i.e., proportional
to the channel current.
sense element R
.
SENSE
The same capacitor C is needed to match the time delay
T
between ISEN- and ISEN+ signals. Select the proper C to
T
keep the time constant of R
to 27ns.
and C (R
ISEN
x C ) close
T
ISEN
T
FN9286.0
April 21, 2006
12
ISL6326B
Equation 7 shows the ratio of the channel current to the
The sensed average current I
is tied to FB internally.
AVG
sensed current I
.
This current will develop voltage drop across the resistor
between FB and VDIFF pins for droop control. ISL6326B
can not be used for non-droop applications.
SEN
R
SENSE
-----------------------
I
= I
⋅
(EQ. 7)
SEN
L
R
ISEN
The output of the error amplifier, V
, is compared to
COMP
I
sawtooth waveforms to generate the PWM signals. The
PWM signals control the timing of the Intersil MOSFET
drivers and regulate the converter output to the specified
reference voltage. The internal and external circuitry which
control voltage regulation is illustrated in Figure 5.
L
L
R
V
OUT
SENSE
C
OUT
ISL6326B INTERNAL CIRCUIT
R
ISEN(n)
EXTERNAL CIRCUIT
ISL6326B INTERNAL CIRCUIT
I
n
R
C
C
C
COMP
DAC
CURRENT
SENSE
ISEN-(n)
ISEN+(n)
+
-
R
REF
REF
C
C
REF
T
+
R
SENSE
-
V
I
FB
COMP
= I --------------------------
SEN
L
R
ISEN
ERROR AMPLIFIER
+
V
-
R
FB
FIGURE 4. SENSE RESISTOR IN SERIES WITH INDUCTORS
DROOP
I
AVG
VDIFF
VSEN
RGND
The inductor DCR value will increase as the temperature
increases. Therefore the sensed current will increase as the
temperature of the current sense element increases. In order
to compensate the temperature effect on the sensed current
signal, a Positive Temperature Coefficient (PTC) resistor can
V
V
+
OUT
+
-
-
OUT
be selected for the sense resistor R
, or the integrated
ISEN
DIFFERENTIAL
REMOTE-SENSE
AMPLIFIER
temperature compensation function of ISL6326B should be
utilized. The integrated temperature compensation function
is described in the Temperature Compensation section.
FIGURE 5. OUTPUT VOLTAGE AND LOAD-LINE
REGULATION WITH OFFSET ADJUSTMENT
Channel-Current Balance
The sensed current I from each active channel are summed
n
together and divided by the number of active channels. The
The ISL6326B incorporates an internal differential remote-
sense amplifier in the feedback path. The amplifier removes
the voltage error encountered when measuring the output
voltage relative to the local controller ground reference point
resulting in a more accurate means of sensing output
voltage. Connect the microprocessor sense pins to the non-
inverting input, VSEN, and inverting input, RGND, of the
resulting average current I
provides a measure of the
AVG
total load current. Channel current balance is achieved by
comparing the sensed current of each channel to the
average current to make an appropriate adjustment to the
PWM duty cycle of each channel with Intersil’s patented
current-balance method.
remote-sense amplifier. The remote-sense output, V
, is
DIFF
Channel current balance is essential in achieving the
thermal advantage of multiphase operation. With good
current balance, the power loss is equally dissipated over
multiple devices and a greater area.
connected to the inverting input of the error amplifier through
an external resistor.
A digital-to-analog converter (DAC) generates a reference
voltage based on the state of logic signals at pins VID7
through VID0. The DAC decodes the eight 6-bit logic signal
(VID) into one of the discrete voltages shown in Table 1.
Each VID input offers a 45µA pull-up to an internal 2.5V
source for use with open-drain outputs. The pull-up current
diminishes to zero above the logic threshold to protect
voltage-sensitive output devices. External pull-up resistors
can augment the pull-up current sources if case leakage into
the driving device is greater than 45µA.
Voltage Regulation
The compensation network shown in Figure 5 assures that
the steady-state error in the output voltage is limited only to
the error in the reference voltage (output of the DAC) and
offset errors in the OFS current source, remote-sense and
error amplifiers. Intersil specifies the guaranteed tolerance of
the ISL6326B to include the combined tolerances of each of
these elements.
FN9286.0
April 21, 2006
13
ISL6326B
TABLE 1. VR10 VID TABLE (WITH 6.25mV EXTENSION)
TABLE 1. VR10 VID TABLE (WITH 6.25mV EXTENSION)
(Continued)
VID4 VID3 VID2 VID1 VID0 VID5
VID6 VOLTAGE
VID4 VID3 VID2 VID1 VID0 VID5
VID6 VOLTAGE
400mV 200mV 100mV 50mV 25mV 12.5mV 6.25mV
(V)
400mV 200mV 100mV 50mV 25mV 12.5mV 6.25mV
(V)
1.35625
1.35
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
1.6
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1.59375
1.5875
1.58125
1.575
1.34375
1.3375
1.33125
1.325
1.56875
1.5625
1.55625
1.55
1.31875
1.3125
1.30625
1.3
1.54375
1.5375
1.53125
1.525
1.29375
1.2875
1.28125
1.275
1.51875
1.5125
1.50625
1.5
1.26875
1.2625
1.25625
1.25
1.49375
1.4875
1.48125
1.475
1.24375
1.2375
1.23125
1.225
1.46875
1.4625
1.45625
1.45
1.21875
1.2125
1.20625
1.2
1.44375
1.4375
1.43125
1.425
1.19375
1.1875
1.18125
1.175
1.41875
1.4125
1.40625
1.4
1.16875
1.1625
1.15625
1.15
1.39375
1.3875
1.38125
1.375
1.14375
1.1375
1.13125
1.125
1.36875
1.3625
1.11875
FN9286.0
April 21, 2006
14
ISL6326B
TABLE 1. VR10 VID TABLE (WITH 6.25mV EXTENSION)
(Continued)
TABLE 1. VR10 VID TABLE (WITH 6.25mV EXTENSION)
(Continued)
VID4 VID3 VID2 VID1 VID0 VID5
VID6 VOLTAGE
VID4 VID3 VID2 VID1 VID0 VID5
VID6 VOLTAGE
400mV 200mV 100mV 50mV 25mV 12.5mV 6.25mV
(V)
1.1125
1.10625
1.1
400mV 200mV 100mV 50mV 25mV 12.5mV 6.25mV
(V)
0.89375
0.8875
0.88125
0.875
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
1
1
1
0
0
0
0
1
1
1
1
0
0
1
0
0
1
1
0
0
1
1
0
0
0
1
0
1
0
1
0
1
0
1
0
1.09375
OFF
0.86875
0.8625
0.85625
0.85
OFF
OFF
OFF
1.0875
1.08125
1.075
0.84375
0.8375
0.83125
1.06875
1.0625
1.05625
1.05
TABLE 2. VR11 VID 8 BIT
VID7 VID6 VID5 VID4 VID3 VID2 VID1 VID0 VOLTAGE
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
OFF
OFF
1.04375
1.0375
1.03125
1.025
1.60000
1.59375
1.58750
1.58125
1.57500
1.56875
1.56250
1.55625
1.55000
1.54375
1.53750
1.53125
1.52500
1.51875
1.51250
1.50625
1.50000
1.49375
1.48750
1.48125
1.47500
1.46875
1.46250
1.01875
1.0125
1.00625
1
0.99375
0.9875
0.98125
0.975
0.96875
0.9625
0.95625
0.95
0.94375
0.9375
0.93125
0.925
0.91875
0.9125
0.90625
0.9
FN9286.0
April 21, 2006
15
ISL6326B
TABLE 2. VR11 VID 8 BIT (Continued)
VID7 VID6 VID5 VID4 VID3 VID2 VID1 VID0 VOLTAGE
TABLE 2. VR11 VID 8 BIT (Continued)
VID7 VID6 VID5 VID4 VID3 VID2 VID1 VID0 VOLTAGE
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1.45625
1.45000
1.44375
1.43750
1.43125
1.42500
1.41875
1.41250
1.40625
1.40000
1.39375
1.38750
1.38125
1.37500
1.36875
1.36250
1.35625
1.35000
1.34375
1.33750
1.33125
1.32500
1.31875
1.31250
1.30625
1.30000
1.29375
1.28750
1.28125
1.27500
1.26875
1.26250
1.25625
1.25000
1.24375
1.23750
1.23125
1.22500
1.21875
1.21250
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1.20625
1.20000
1.19375
1.18750
1.18125
1.17500
1.16875
1.16250
1.15625
1.15000
1.14375
1.13750
1.13125
1.12500
1.11875
1.11250
1.10625
1.10000
1.09375
1.08750
1.08125
1.07500
1.06875
1.06250
1.05625
1.05000
1.04375
1.03750
1.03125
1.02500
1.01875
1.01250
1.00625
1.00000
0.99375
0.98750
0.98125
0.97500
0.96875
0.96250
FN9286.0
April 21, 2006
16
ISL6326B
TABLE 2. VR11 VID 8 BIT (Continued)
VID7 VID6 VID5 VID4 VID3 VID2 VID1 VID0 VOLTAGE
TABLE 2. VR11 VID 8 BIT (Continued)
VID7 VID6 VID5 VID4 VID3 VID2 VID1 VID0 VOLTAGE
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
0.95625
0.95000
0.94375
0.93750
0.93125
0.92500
0.91875
0.91250
0.90625
0.90000
0.89375
0.88750
0.88125
0.87500
0.86875
0.86250
0.85625
0.85000
0.84375
0.83750
0.83125
0.82500
0.81875
0.81250
0.80625
0.80000
0.79375
0.78750
0.78125
0.77500
0.76875
0.76250
0.75625
0.75000
0.74375
0.73750
0.73125
0.72500
0.71875
0.71250
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
1
1
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
1
1
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
0
1
0.70625
0.70000
0.69375
0.68750
0.68125
0.67500
0.66875
0.66250
0.65625
0.65000
0.64375
0.63750
0.63125
0.62500
0.61875
0.61250
0.60625
0.60000
0.59375
0.58750
0.58125
0.57500
0.56875
0.56250
0.55625
0.55000
0.54375
0.53750
0.53125
0.52500
0.51875
0.51250
0.50625
0.50000
OFF
OFF
FN9286.0
April 21, 2006
17
ISL6326B
Load-Line Regulation
Output-Voltage Offset Programming
The ISL6326B allows the designer to accurately adjust the
offset voltage. When a resistor, R , is connected between
Some microprocessor manufacturers require a precisely-
controlled output resistance. This dependence of output
voltage on load current is often termed “droop” or “load line”
regulation. By adding a well controlled output impedance,
the output voltage can effectively be level shifted in a
direction which works to achieve the load-line regulation
required by these manufacturers.
OFS
OFS to VCC, the voltage across it is regulated to 1.6V. This
causes a proportional current (I ) to flow into OFS. If
OFS
is connected to ground, the voltage across it is
R
OFS
regulated to 0.4V, and I
flows out of OFS. A resistor
OFS
between DAC and REF, R
, is selected so that the
REF
product (I
x R
) is equal to the desired offset voltage.
OFS
OFS
In other cases, the designer may determine that a more
cost-effective solution can be achieved by adding droop.
Droop can help to reduce the output-voltage spike that
results from fast load-current demand changes.
These functions are shown in Figure 6.
Once the desired output offset voltage has been determined,
use the following formulas to set R
:
OFS
The magnitude of the spike is dictated by the ESR and ESL
of the output capacitors selected. By positioning the no-load
voltage level near the upper specification limit, a larger
negative spike can be sustained without crossing the lower
limit. By adding a well controlled output impedance, the
output voltage under load can effectively be level shifted
down so that a larger positive spike can be sustained without
crossing the upper specification limit.
For Positive Offset (connect R
to VCC):
OFS
1.6 × R
REF
(EQ. 11)
(EQ. 12)
-----------------------------
R
=
OFS
V
OFFSET
For Negative Offset (connect R
to GND):
OFS
0.4 × R
REF
-----------------------------
R
=
OFS
V
OFFSET
As shown in Figure 5, a current proportional to the average
current of all active channels, I
, flows from FB through a
AVG
FB
load-line regulation resistor R . The resulting voltage drop
FB
across R is proportional to the output current, effectively
FB
creating an output voltage droop with a steady-state value
defined as
DAC
DYNAMIC
VID D/A
V
= I
R
(EQ. 8)
DROOP
AVG FB
R
REF
E/A
REF
The regulated output voltage is reduced by the droop voltage
. The output voltage as a function of load current is
C
REF
V
DROOP
derived by combining Equation 8 with the appropriate
sample current expression defined by the current sense
method employed.
VCC
OR
GND
I
R
X
R
ISEN
⎛
⎞
⎟
⎠
LOAD
N
V
= V
– V
– ---------------- ----------------- R
⎜
OFS FB
(EQ. 9)
OUT
REF
⎝
-
1.6V
+
Where V
is the reference voltage, V
is the
REF
programmed offset voltage, I
OFS
R
OFS
is the total output current
+
-
LOAD
is the sense resistor connected to
0.4V
of the converter, R
the ISEN+ pin, and R is the feedback resistor, N is the
ISEN
OFS
ISL6326B
FB
active channel number, and R is the DCR, or R
GND
X
SENSE
VCC
depending on the sensing method.
FIGURE 6. OUTPUT VOLTAGE OFFSET PROGRAMMING
Therefore the equivalent loadline impedance, i.e. Droop
impedance, is equal to:
R
R
X
R
ISEN
FB
R
= ------------ -----------------
(EQ. 10)
LL
N
FN9286.0
April 21, 2006
18
ISL6326B
ISL66xx family of Intersil MOSFET drivers, which require
12V bias.
Dynamic VID
Modern microprocessors need to make changes to their
core voltage as part of normal operation. They direct the
core-voltage regulator to do this by making changes to the
VID inputs during regulator operation. The power
management solution is required to monitor the DAC inputs
and respond to on-the-fly VID changes in a controlled
manner. Supervising the safe output voltage transition within
the DAC range of the processor without discontinuity or
disruption is a necessary function of the core-voltage
regulator.
3. The voltage on EN_VTT must be higher than 0.875V to
enable the controller. This pin is typically connected to the
output of VTT VR.
ISL6326B INTERNAL CIRCUIT
EXTERNAL CIRCUIT
+12V
VCC
10kΩ
POR
ENABLE
COMPARATOR
CIRCUIT
EN_PWR
+
-
In order to ensure the smooth transition of output voltage
during VID change, a VID step change smoothing network,
910Ω
composed of R
and C
as shown in Figure 6, can be
is based on the desired offset
REF
REF
used. The selection of R
REF
voltage as detailed above in Output-Voltage Offset
Programming. The selection of C is based on the time
0.875V
REF
EN_VTT
+
-
duration for 1 bit VID change and the allowable delay time.
Assuming the microprocessor controls the VID change at 1
bit every T , the relationship between the time constant of
VID
R
and C
network and T
is given by the following
0.875V
REF
equation.
REF
VID
SOFT-START
AND
(EQ. 13)
C
R
= T
REF REF
VID
FAULT LOGIC
Operation Initialization
FIGURE 7. POWER SEQUENCING USING THRESHOLD-
SENSITIVE ENABLE (EN) FUNCTION
Prior to converter initialization, proper conditions must exist
on the enable inputs and VCC. When the conditions are met,
the controller begins soft-start. Once the output voltage is
within the proper window of operation, VR_RDY asserts
logic high.
When all conditions above are satisfied, ISL6326B begins
the soft-start and ramps the output voltage to 1.1V first. After
remaining at 1.1V for some time, ISL6326B reads the VID
code at VID input pins. If the VID code is valid, ISL6326B will
regulate the output to the final VID setting. If the VID code is
OFF code, ISL6326B will shut down, and cycling VCC,
EN_PWR or EN_VTT is needed to restart.
Enable and Disable
While in shutdown mode, the PWM outputs are held in a
high-impedance state to assure the drivers remain off. The
following input conditions must be met before the ISL6326B
is released from shutdown mode.
Soft-Start
ISL6326B based VR has 4 periods during soft-start as
shown in Figure 8. After VCC, EN_VTT and EN_PWR reach
their POR/enable thresholds, The controller will have fixed
delay period TD1. After this delay period, the VR will begin
first soft-start ramp until the output voltage reaches 1.1V
Vboot voltage. Then, the controller will regulate the VR
voltage at 1.1V for another fixed period TD3. At the end of
TD3 period, ISL6326B reads the VID signals. If the VID code
is valid, ISL6326B will initiate the second soft-start ramp until
the voltage reaches the VID voltage minus offset voltage.
1. The bias voltage applied at VCC must reach the internal
power-on reset (POR) rising threshold. Once this
threshold is reached, proper operation of all aspects of
the ISL6326B is guaranteed. Hysteresis between the
rising and falling thresholds assure that once enabled,
the ISL6326B will not inadvertently turn off unless the
bias voltage drops substantially (see Electrical
Specifications).
2. The ISL6326B features an enable input (EN_PWR) for
power sequencing between the controller bias voltage
and another voltage rail. The enable comparator holds
the ISL6326B in shutdown until the voltage at EN_PWR
rises above 0.875V. The enable comparator has about
130mV of hysteresis to prevent bounce. It is important
that the driver ICs reach their POR level before the
ISL6326B becomes enabled. The schematic in Figure 7
demonstrates sequencing the ISL6326B with the
The soft-start time is the sum of the 4 periods as shown in
the following equation.
T
= TD1 + TD2 + TD3 + TD4
(EQ. 14)
SS
TD1 is a fixed delay with the typical value as 1.36ms. TD3 is
determined by the fixed 85µs plus the time to obtain valid
FN9286.0
April 21, 2006
19
ISL6326B
VID voltage. If the VID is valid before the output reaches the
either the DCR of the inductor or R depending on the
SENSE
1.1V, the minimum time to validate the VID input is 500ns.
Therefore the minimum TD3 is about 86µs.
sensing method.
The resistor from the IOUT pin to GND should be chosen to
ensure that the voltage at the IOUT pin is less than 2V under
the maximum load current. If the IOUT pin voltage is higher
than 2V, overcurrent shutdown will be triggered, as
described in the Overcurrent Protection section.
During TD2 and TD4, ISL6326B digitally controls the DAC
voltage change at 6.25mV per step. The time for each step is
determined by the frequency of the soft-start oscillator which
is defined by the resistor R from SS pin to GND. The
SS
A small capacitor can be placed between the IOUT pin and
GND to reduce the noise impact. If this pin is not used, tie it
to GND.
second soft-start ramp time TD2 and TD4 can be calculated
based on the following equations:
1.1xR
SS
-----------------------
TD2 =
(μs)
(EQ. 15)
6.25x25
Fault Monitoring and Protection
(V – 1.1)xR
The ISL6326B actively monitors output voltage and current
to detect fault conditions. Fault monitors trigger protective
measures to prevent damage to a microprocessor load. One
common power good indicator is provided for linking to
external system monitors. The schematic in Figure 9 outlines
the interaction between the fault monitors and the VR_RDY
signal.
VID
SS
(EQ. 16)
------------------------------------------------
TD4 =
(μs)
6.25x25
For example, when VID is set to 1.5V and the R is set at
SS
100kΩ, the first soft-start ramp time TD2 will be 704µs and
the second soft-start ramp time TD4 will be 256µs.
After the DAC voltage reaches the final VID setting,
VR_RDY will be set to high with the fixed delay TD5. The
typical value for TD5 is 85µs.
VR_RDY Signal
The VR_RDY pin is an open-drain logic output to indicate
that the soft-start period has completed and the output
voltage is within the regulated range. VR_RDY is pulled low
during shutdown and releases high after a successful soft-
start and a fixed delay TD5. VR_RDY will be pulled low when
an undervoltage or overvoltage condition is detected, or the
controller is disabled by a reset from EN_PWR, EN_VTT,
POR, or VID OFF-code.
VOUT, 500mV/DIV
TD1
TD5
TD3 TD4
TD2
Undervoltage Detection
The undervoltage threshold is set at 50% of the VID code.
When the output voltage at VSEN is below the undervoltage
threshold, VR_RDY is pulled low.
EN_VTT
Overvoltage Protection
VR_RDY
500µs/DIV
Regardless of the VR being enabled or not, the ISL6326B
overvoltage protection (OVP) circuit will be active after its
POR. The OVP thresholds are different under different
operation conditions. When VR is not enabled and during
the soft-start intervals TD1, TD2 and TD3, the OVP
threshold is 1.275V. Once the controller detects valid VID
input, the OVP trip point will be changed to DAC plus
175mV.
FIGURE 8. SOFT-START WAVEFORMS
Current Sense Output
The current flowing out of the IOUT pin is equal to the
sensed average current inside ISL6326B. In typical
application, a resistor is placed from the IOUT pin to GND to
generate a voltage, which is proportional to the load current
and the resistor value:
Two actions are taken by the ISL6326B to protect the
microprocessor load when an overvoltage condition occurs.
R
R
X
R
ISEN
At the inception of an overvoltage event, all PWM outputs
are commanded low instantly (less than 20ns). This causes
the Intersil drivers to turn on the lower MOSFETs and pull
the output voltage below a level to avoid damaging the load.
When the VDIFF voltage falls below the DAC plus 75mV,
PWM signals enter a high-impedance state. The Intersil
drivers respond to the high-impedance input by turning off
both upper and lower MOSFETs. If the overvoltage condition
reoccurs, the ISL6326B will again command the lower
IOUT
N
(EQ. 17)
V
= ------------------ -----------------I
IOUT
LOAD
where V
is the voltage at the IOUT pin, R
is the
is the total
IOUT
IOUT
resistor between the IOUT pin and GND, I
output current of the converter, R
connected to the ISEN+ pin, N is the active channel number,
and R is the DC resistance of the current sense element,
X
LOAD
is the sense resistor
ISEN
FN9286.0
April 21, 2006
20
ISL6326B
MOSFETs to turn on. The ISL6326B will continue to protect
the load in this fashion as long as the overvoltage condition
occurs.
At the beginning of overcurrent shutdown, the controller
places all PWM signals in a high-impedance state within
20ns, commanding the Intersil MOSFET driver ICs to turn off
both upper and lower MOSFETs. The system remains in this
state a period of 4096 switching cycles. If the controller is still
enabled at the end of this wait period, it will attempt a soft-
start. If the fault remains, the trip-retry cycles will continue
indefinitely (as shown in Figure 10) until either controller is
disabled or the fault is cleared. Note that the energy
delivered during trip-retry cycling is much less than during
full-load operation, so there is no thermal hazard during this
kind of operation.
Once an overvoltage condition is detected, normal PWM
operation ceases until the ISL6326B is reset. Cycling the
voltage on EN_PWR, EN_VTT or VCC below the POR-
falling threshold will reset the controller. Cycling the VID
codes will not reset the controller.
VR_RDY
UV
OUTPUT CURRENT
50%
85µA
-
DAC
SOFT-START, FAULT
AND CONTROL LOGIC
OC
+
0A
I
AVG
2.0V
-
VDIFF
+
OUTPUT VOLTAGE
OC
OV
IOUT
+
-
VID + 0.175V
0V
2ms/DIV
FIGURE 9. VR_RDY AND PROTECTION CIRCUITRY
FIGURE 10. OVERCURRENT BEHAVIOR IN HICCUP MODE.
F
= 500kHz
SW
Overcurrent Protection
ISL6326B has two levels of overcurrent protection. Each
phase is protected from a sustained overcurrent condition by
limiting its peak current, while the combined phase currents
are protected on an instantaneous basis.
For the individual channel overcurrent protection, the
ISL6326B continuously compares the sensed current signal
of each channel with the 120µA reference current. If one
channel current exceeds the reference current, ISL6326B
will pull PWM signal of this channel to low for the rest of the
switching cycle. This PWM signal can be turned on next
cycle if the sensed channel current is less than the 120µA
reference current. The peak current limit of individual
channel will not trigger the converter to shutdown.
In instantaneous protection mode, ISL6326B utilizes the
sensed average current I
to detect an overcurrent
AVG
condition. See the Channel-Current Balance section for
more detail on how the average current is measured. The
average current is continually compared with a constant
85µA reference current, as shown in Figure 9. Once the
average current exceeds the reference current, a
comparator triggers the converter to shutdown.
Thermal Monitoring (VR_HOT/VR_FAN)
There are two thermal signals to indicate the temperature
status of the voltage regulator: VR_HOT and VR_FAN. Both
VR_FAN and VR_HOT pins are open-drain outputs, and
external pull-up resistors are required. Those signals are
valid only after the controller is enabled.
The current out of IOUT pin is equal to the sensed average
current I
. With a resistor from IOUT to GND, the voltage
AVG
at IOUT will be proportional to the sensed average current
and the resistor value. ISL6326B continuously monitors the
voltage at IOUT pin. If the voltage at IOUT pin is higher than
2V, a comparator triggers the overcurrent shutdown. By
increasing the resistor between IOUT and GND, the
The VR_FAN signal indicates that the temperature of the
voltage regulator is high and more cooling airflow is needed.
The VR_HOT signal can be used to inform the system that
the temperature of the voltage regulator is too high and the
CPU should reduce its power consumption. The VR_HOT
signal may be tied to the CPU’s PROC_HOT signal.
overcurrent protection threshold can be adjusted to be less
than 100µA. For example, the overcurrent threshold for the
sensed average current I
can be set to 80µA by using a
AVG
25kΩ resistor from IOUT to GND.
FN9286.0
April 21, 2006
21
ISL6326B
The diagram of thermal monitoring function block is shown in
VTM / VCC vs. Temperature
Figure 11. One NTC resistor should be placed close to the
power stage of the voltage regulator to sense the operational
temperature, and one pull-up resistor is needed to form the
voltage divider for the TM pin. As the temperature of the
power stage increases, the resistance of the NTC will
reduce, resulting in the reduced voltage at the TM pin.
Figure 12 shows the TM voltage over the temperature for a
typical design with a recommended 6.8kΩ NTC (P/N:
NTHS0805N02N6801 from Vishay) and 1kΩ resistor RTM1.
We recommend using those resistors for the accurate
temperature compensation.
100%
90%
80%
70%
60%
50%
40%
30%
20%
There are two comparators with hysteresis to compare the
TM pin voltage to the fixed thresholds for VR_FAN and
VR_HOT signals respectively. The VR_FAN signal is set to
high when the TM voltage is lower than 33% of VCC voltage,
and is pulled to GND when the TM voltage increases to
above 39% of VCC voltage. The VR_FAN signal is set to
high when the TM voltage goes below 28% of VCC voltage,
and is pulled to GND when the TM voltage goes back to
above 33% of VCC voltage. Figure 13 shows the operation
of those signals.
0
20
40
60
80
100
120
140
Temperature (oC)
FIGURE 12. THE RATIO OF TM VOLTAGE TO NTC
TEMPERATURE WITH RECOMMENDED PARTS
TM
0.39*Vcc
0.33*Vcc
0.28*Vcc
VR_FAN
VR_HOT
VCC
VR_FAN
Temperature
T1
T2
T3
0.33VCC
RTM1
FIGURE 13. VR_HOT AND VR_FAN SIGNAL vs TM VOLTAGE
VR_HOT
TM
Based on the NTC temperature characteristics and the
desired threshold of the VR_HOT signal, the pull-up resistor
RTM1 of TM pin is given by:
oc
RNTC
0.28VCC
R
= 2.75xR
NTC(T3)
(EQ. 18)
TM1
FIGURE 11. BLOCK DIAGRAM OF THERMAL MONITORING
FUNCTION
R
is the NTC resistance at the VR_HOT threshold
NTC(T3)
temperature T3.
The NTC resistance at the set point T2 and release point T1
of VR_FAN signal can be calculated as:
R
= 1.267xR
(EQ. 19)
NTC(T2)
NTC(T3)
R
= 1.644xR
(EQ. 20)
NTC(T1)
NTC(T3)
With the NTC resistance value obtained from Equations 19
and 20, the temperature value T2 and T1 can be found from
the NTC datasheet.
FN9286.0
April 21, 2006
22
ISL6326B
component. The TCOMP pin voltage can be utilized to
Temperature Compensation
correct the temperature difference between NTC and the
current sense component. When a different NTC type or
different voltage divider is used for the TM function, the
TCOMP voltage can also be used to compensate for the
difference between the recommended TM voltage curve in
Figure 13 and that of the actual design. According to the
VCC voltage, ISL6326B converts the TCOMP pin voltage to
a 4-bit TCOMP digital signal as TCOMP factor N.
ISL6326B supports inductor DCR sensing, or resistive
sensing techniques. The inductor DCR has a positive
temperature coefficient, which is about +0.38%/°C. Since the
voltage across inductor is sensed for the output current
information, the sensed current has the same positive
temperature coefficient as the inductor DCR.
In order to obtain the correct current information, there
should be a way to correct the temperature impact on the
current sense component. ISL6326B provides two methods:
integrated temperature compensation and external
temperature compensation.
The TCOMP factor N is an integer between 0 and 15. The
integrated temperature compensation function is disabled for
N = 0. For N = 4, the NTC temperature is equal to the
temperature of the current sense component. For N < 4, the
NTC is hotter than the current sense component. The NTC is
cooler than the current sense component for N > 4. When
N > 4, the larger TCOMP factor N, the larger the difference
between the NTC temperature and the temperature of the
current sense component.
Integrated Temperature Compensation
When the TCOMP voltage is equal or greater than VCC/15,
ISL6326B will utilize the voltage at TM and TCOMP pins to
compensate the temperature impact on the sensed current.
The block diagram of this function is shown in Figure 14.
ISL6326B multiplexes the TCOMP factor N with the TM
digital signal to obtain the adjustment gain to compensate
the temperature impact on the sensed channel current. The
compensated channel current signal is used for droop and
overcurrent protection functions.
VCC
Isen4
Isen3
Isen2
Isen1
Channel current
sense
RTM1
Design Procedure
Non-linear
A/D
TM
1. Properly choose the voltage divider for the TM pin to
match the TM voltage vs temperature curve with the
recommended curve in Figure 12.
I4
I3
I2
I1
oc
RNTC
2. Run the actual board under the full load and the desired
cooling condition.
ki
D/A
VCC
3. After the board reaches the thermal steady state, record
the temperature (T
(inductor or MOSFET) and the voltage at TM and VCC
pins.
) of the current sense component
CSC
RTC1
TCOMP
4-bit
A/D
Droop &
Over current protection
4. Use the following equation to calculate the resistance of
the TM NTC, and find out the corresponding NTC
RTC2
temperature T
from the NTC datasheet.
NTC
V
xR
TM
TM1
(EQ. 21)
R
= -------------------------------
)
NTC
FIGURE 14. BLOCK DIAGRAM OF INTEGRATED
TEMPERATURE COMPENSATION
NTC(T
V
– V
CC
TM
5. Use the following equation to calculate the TCOMP
factor N:
When the TM NTC is placed close to the current sense
component (inductor), the temperature of the NTC will track
the temperature of the current sense component. Therefore
the TM voltage can be utilized to obtain the temperature of
the current sense component.
209x(T
– T
)
NTC
CSC
(EQ. 22)
-------------------------------------------------------
N =
+ 4
3xT
+ 400
NTC
6. Choose an integral number close to the above result for
the TCOMP factor. If this factor is higher than 15, use
N = 15. If it is less than 1, use N = 1.
Based on VCC voltage, ISL6326B converts the TM pin
voltage to a 6-bit TM digital signal for temperature
7. Choose the pull-up resistor R
TC1
(typical 10kΩ);
compensation. With the non-linear A/D converter of
ISL6326B, the TM digital signal is linearly proportional to the
NTC temperature. For accurate temperature compensation,
the ratio of the TM voltage to the NTC temperature of the
practical design should be similar to that in Figure 12.
8. If N = 15, do not need the pull-down resistor R
,
TC2
otherwise obtain R
by the following equation:
TC2
NxR
TC1
15 – N
----------------------
=
(EQ. 23)
R
TC2
9. Run the actual board under full load again with the proper
resistors connected to the TCOMP pin.
Depending on the location of the NTC and the airflow, the
NTC may be cooler or hotter than the current sense
FN9286.0
April 21, 2006
23
ISL6326B
10. Record the output voltage as V1 immediately after the
output voltage is stable with the full load. Record the
output voltage as V2 after the VR reaches the thermal
steady state.
Power Stages
The first step in designing a multiphase converter is to
determine the number of phases. This determination
depends heavily on the cost analysis which in turn depends
on system constraints that differ from one design to the next.
Principally, the designer will be concerned with whether
components can be mounted on both sides of the circuit
board; whether through-hole components are permitted; and
the total board space available for power-supply circuitry.
Generally speaking, the most economical solutions are
those in which each phase handles between 15 and 20A. All
surface-mount designs will tend toward the lower end of this
current range. If through-hole MOSFETs and inductors can
be used, higher per-phase currents are possible. In cases
where board space is the limiting constraint, current can be
pushed as high as 40A per phase, but these designs require
heat sinks and forced air to cool the MOSFETs, inductors
and heat-dissipating surfaces.
11. If the output voltage increases over 2mV as the
temperature increases, i.e. V2-V1 > 2mV, reduce N and
redesign R
; if the output voltage decreases over 2mV
TC2
as the temperature increases, i.e. V1-V2 > 2mV, increase
N and redesign R
.
TC2
External Temperature Compensation
By pulling the TCOMP pin to GND, the integrated
temperature compensation function is disabled. And one
external temperature compensation network, shown in
Figure 15, can be used to cancel the temperature impact on
the droop (i.e., load line).
ISL6326B
Internal
circuit
COMP
MOSFETs
The choice of MOSFETs depends on the current each
MOSFET will be required to conduct; the switching
frequency; the capability of the MOSFETs to dissipate heat;
and the availability and nature of heat sinking and air flow.
FB
oC
ISEN
LOWER MOSFET POWER CALCULATION
The calculation for heat dissipated in the lower MOSFET is
simple, since virtually all of the heat loss in the lower
MOSFET is due to current conducted through the channel
VDIFF
FIGURE 15. EXTERNAL TEMPERATURE COMPENSATION
resistance (R
). In Equation 24, I is the maximum
DS(ON)
M
continuous output current; I is the peak-to-peak inductor
PP
The sensed current will flow out of the FB pin and develop a
current (see Equation 1); d is the duty cycle (V
/V ); and
droop voltage across the resistor equivalent (R ) between
OUT IN
FB
L is the per-channel inductance.
the FB and VDIFF pins. If R resistance reduces as the
FB
temperature increases, the temperature impact on the droop
can be compensated. An NTC resistor can be placed close
to the power stage and used to form R . Due to the
FB
2
2
I
(1 – d)
⎛
⎜
⎝
⎞
⎟
⎠
I
L, PP
(EQ. 24)
M
P
= r
(1 – d) + --------------------------------
-----
LOW, 1
DS(ON)
12
N
non-linear temperature characteristics of the NTC, a resistor
network is needed to make the equivalent resistance
between the FB and VDIFF pins reverse proportional to the
temperature.
An additional term can be added to the lower-MOSFET loss
equation to account for additional loss accrued during the
dead time when inductor current is flowing through the
lower-MOSFET body diode. This term is dependent on the
The external temperature compensation network can only
compensate the temperature impact on the droop, while it
has no impact to the sensed current inside ISL6326B.
Therefore, this network cannot compensate for the
temperature impact on the overcurrent protection function.
diode forward voltage at I , V ; the switching
M
D(ON)
frequency, f ; and the length of dead times, t and t , at
S
d1 d2
the beginning and the end of the lower-MOSFET conduction
interval respectively.
⎛
⎜
⎝
⎞
⎟
⎠
I
I
M
N
I
I
(EQ. 25)
⎛
⎝
⎞
⎠
M
PP
2
PP
2
P
= V
f
D(ON) S
t
t
d2
+
--------
----- –
----- + --------
LOW, 2
d1
N
General Design Guide
This design guide is intended to provide a high-level
explanation of the steps necessary to create a multiphase
power converter. It is assumed that the reader is familiar with
many of the basic skills and techniques referenced below. In
addition to this guide, Intersil provides complete reference
designs that include schematics, bills of materials, and
example board layouts for all common microprocessor
applications.
Thus the total maximum power dissipated in each lower
MOSFET is approximated by the summation of P
and
LOW,1
P
.
LOW,2
Upper MOSFET Power Calculation
In addition to R losses, a large portion of the upper-
DS(ON)
MOSFET losses are due to currents conducted across the
input voltage (V ) during switching. Since a substantially
IN
FN9286.0
April 21, 2006
24
ISL6326B
higher portion of the upper-MOSFET losses are dependent
where R is the sense resistor connected to the ISEN+
ISEN
on switching frequency, the power calculation is more
complex. Upper MOSFET losses can be divided into
separate components involving the upper-MOSFET
switching times; the lower-MOSFET body-diode reverse-
pin, N is the active channel number, R is the resistance of
the current sense element, either the DCR of the inductor or
X
R
depending on the sensing method, and I
is the
SENSE
desired overcurrent trip point. Typically, I
OCP
can be chosen
OCP
recovery charge, Q ; and the upper MOSFET R
to be 1.3 times the maximum load current of the specific
rr
DS(ON)
conduction loss.
application.
When the upper MOSFET turns off, the lower MOSFET does
not conduct any portion of the inductor current until the
voltage at the phase node falls below ground. Once the
lower MOSFET begins conducting, the current in the upper
MOSFET falls to zero as the current in the lower MOSFET
ramps up to assume the full inductor current. In Equation 26,
With integrated temperature compensation, the sensed
current signal is independent on the operational temperature
of the power stage, i.e. the temperature effect on the current
sense element R is cancelled by the integrated
X
temperature compensation function. R in Equation 30
X
should be the resistance of the current sense element at the
room temperature.
the required time for this commutation is t and the
1
approximated associated power loss is P
.
UP,1
When the integrated temperature compensation function is
disabled by pulling the TCOMP pin to GND, the sensed
current will be dependent on the operational temperature of
the power stage, since the DC resistance of the current
sense element may be changed according to the operational
t
I
I
⎛
⎜
⎝
⎞
⎟
⎠
1
M
PP
2
⎛
⎝
⎞
(EQ. 26)
P
≈ V
f
S
----
----- + --------
UP,1
IN
⎠
2
N
At turn on, the upper MOSFET begins to conduct and this
transition occurs over a time t . In Equation 27, the
temperature. R in Equation 30 should be the maximum DC
2
X
approximate power loss is P
.
resistance of the current sense element at the all operational
temperature.
UP,2
I
t
2
2
⎛I
⎞ ⎛
⎞
⎟
⎠
PP
2
M
(EQ. 27)
P
≈ V
f
S
-------- ----
⎟ ⎜
⎜
⎝
----- –
UP,2
IN
In certain circumstances, it may be necessary to adjust the
value of one or more ISEN resistors. When the components
of one or more channels are inhibited from effectively
dissipating their heat so that the affected channels run hotter
than desired, choose new, smaller values of RISEN for the
affected phases (see the section entitled Channel-Current
N
⎠ ⎝
A third component involves the lower MOSFET’s reverse-
recovery charge, Q . Since the inductor current has fully
rr
commutated to the upper MOSFET before the lower-
MOSFET’s body diode can draw all of Q , it is conducted
through the upper MOSFET across VIN. The power
rr
Balance). Choose R
in proportion to the desired
ISEN,2
decrease in temperature rise in order to cause proportionally
less current to flow in the hotter phase:
dissipated as a result is P
and is approximately
UP,3
P
= V
Q f
(EQ. 28)
UP,3
IN rr S
ΔT
2
(EQ. 31)
R
= R
----------
ISEN,2
ISEN
ΔT
1
Finally, the resistive part of the upper MOSFET’s is given in
Equation 29 as P
.
UP,4
In Equation 31, make sure that ΔT is the desired temperature
2
rise above the ambient temperature, and ΔT is the measured
temperature rise above the ambient temperature. While a
single adjustment according to Equation 31 is usually
sufficient, it may occasionally be necessary to adjust R
ISEN
two or more times to achieve optimal thermal balance
between all channels.
The total power dissipated by the upper MOSFET at full load
can now be approximated as the summation of the results
from Equations 26, 27, and 28. Since the power equations
depend on MOSFET parameters, choosing the correct
MOSFETs can be an iterative process involving repetitive
solutions to the loss equations for different MOSFETs and
different switching frequencies.
1
Load-Line Regulation Resistor
2
2
I
⎛
⎜
⎝
⎞
⎟
⎠
I
The load-line regulation resistor is labelled R in Figure 5.
FB
Its value depends on the desired loadline requirement of the
PP
M
(EQ. 29)
P
≈ r
d +
d
---------
12
-----
UP,4
DS(ON)
N
application.
Current Sensing Resistor
The desired loadline can be calculated by the following
equation:
The resistors connected to the Isen+ pins determine the
gains in the load-line regulation loop and the channel-current
balance loop as well as setting the overcurrent trip point.
Select values for these resistors by the following equation:
V
DROOP
R
= ------------------------
(EQ. 32)
LL
I
FL
R
I
OCP
N
X
where I is the full load current of the specific application,
FL
(EQ. 30)
R
= ----------------------- -------------
–
ISEN
6
85 ×10
and VR
is the desired voltage droop under the full
DROOP
load condition.
FN9286.0
April 21, 2006
25
ISL6326B
Based on the desired loadline R , the loadline regulation
LL
C
(OPTIONAL)
2
resistor can be calculated by the following equation:
N
R
R
C
C
LL
ISEN
R
X
R
R
= ---------------------------------
C
(EQ. 33)
FB
COMP
FB
where N is the active channel number, R
is the sense
resistor connected to the ISEN+ pin, and R is the
ISEN
X
+
resistance of the current sense element, either the DCR of
R
FB
V
the inductor or R depending on the sensing method.
DROOP
SENSE
-
If one or more of the current sense resistors are adjusted for
thermal balance, as in Equation 31, the load-line regulation
resistor should be selected based on the average value of
the current sensing resistors, as given in the following
equation:
VDIFF
FIGURE 16. COMPENSATION CONFIGURATION FOR
LOAD-LINE REGULATED ISL6326B CIRCUIT
R
LL
R
= ----------
R
ISEN(n)
(EQ. 34)
∑
FB
R
X
n
The feedback resistor, R , has already been chosen as
FB
outlined in Load-Line Regulation Resistor. Select a target
where R
the n ISEN+ pin.
is the current sensing resistor connected to
ISEN(n)
bandwidth for the compensated system, f . The target
0
th
bandwidth must be large enough to assure adequate
transient performance, but smaller than 1/3 of the
per-channel switching frequency. The values of the
compensation components depend on the relationships of f
to the L-C pole frequency and the ESR zero frequency. For
each of the three cases which follow, there is a separate set
of equations for the compensation components.
Compensation
The two opposing goals of compensating the voltage
regulator are stability and speed. Depending on whether the
regulator employs the optional load-line regulation as
described in Load-Line Regulation, there are two distinct
methods for achieving these goals.
0
1
COMPENSATING LOAD-LINE REGULATED
CONVERTER
------------------- > f
Case 1:
Case 2:
Case 3:
0
2π LC
2πf V
LC
pp
0.75V
IN
0
The load-line regulated converter behaves in a similar
manner to a peak-current mode controller because the two
poles at the output-filter L-C resonant frequency split with
the introduction of current information into the control loop.
The final location of these poles is determined by the system
function, the gain of the current signal, and the value of the
compensation components, R and C .
R
C
= R -----------------------------------
C
C
FB
0.75V
IN
2πV
= ------------------------------------
R
f
PP FB 0
1
1
-------------------
≤ f < -----------------------------
0
2πC(ESR)
2π LC
C
C
2
2
Since the system poles and zero are affected by the values
of the components that are meant to compensate them, the
solution to the system equation becomes fairly complicated.
Fortunately there is a simple approximation that comes very
close to an optimal solution. Treating the system as though it
were a voltage-mode regulator by compensating the L-C
poles and the ESR zero of the voltage-mode approximation
yields a solution that is always stable with very close to ideal
transient performance.
V
(2π)
f
LC
0
PP
R
C
= R --------------------------------------------
FB
(EQ. 35)
C
C
0.75 V
0.75V
IN
IN
= ------------------------------------------------------------
2
2
(2π)
f
V
R
LC
0
PP FB
1
f > -----------------------------
0
2πC(ESR)
2π f V
L
pp
0
R
C
= R
-----------------------------------------
FB
C
C
0.75 V (ESR)
IN
0.75V (ESR)
C
IN
= -------------------------------------------------
2πV
R
f
L
PP FB 0
In Equation 35, L is the per-channel filter inductance divided
by the number of active channels; C is the sum total of all
output capacitors; ESR is the equivalent-series resistance of
FN9286.0
April 21, 2006
26
ISL6326B
the bulk output-filter capacitance; and V is the sawtooth
PP
with bulk capacitors having high capacitance but limited
amplitude described in Electrical Specifications.
high-frequency performance. Minimizing the ESL of the
high-frequency capacitors allows them to support the output
voltage as the current increases. Minimizing the ESR of the
bulk capacitors allows them to supply the increased current
with less output voltage deviation.
The optional capacitor C , is sometimes needed to bypass
2
noise away from the PWM comparator. Keep a position
available for C , and be prepared to install a high-frequency
2
capacitor of between 22pF and 150pF in case any leading-
edge jitter problem is noted.
The ESR of the bulk capacitors also creates the majority of
the output-voltage ripple. As the bulk capacitors sink and
source the inductor AC ripple current (see Interleaving and
Equation 2), a voltage develops across the bulk-capacitor
Once selected, the compensation values in Equation 35
assure a stable converter with reasonable transient
performance. In most cases, transient performance can be
ESR equal to I
(ESR). Thus, once the output capacitors
C,PP
are selected, the maximum allowable ripple voltage,
improved by making adjustments to R . Slowly increase the
C
value of R while observing the transient performance on an
C
V , determines the lower limit on the inductance.
PP(MAX)
oscilloscope until no further improvement is noted. Normally,
C
will not need adjustment. Keep the value of C from
⎛
⎝
⎞
V
C
C
V
– N V
IN
OUT
OUT
⎠
(EQ. 37)
Equation 35 unless some performance issue is noted.
L
(ESR)
≥
-----------------------------------------------------------
f V
V
IN PP(MAX)
S
Output Filter Design
Since the capacitors are supplying a decreasing portion of
the load current while the regulator recovers from the
transient, the capacitor voltage becomes slightly depleted.
The output inductors must be capable of assuming the entire
load current before the output voltage decreases more than
The output inductors and the output capacitor bank together
to form a low-pass filter responsible for smoothing the
pulsating voltage at the phase nodes. The output filter also
must provide the transient energy until the regulator can
respond. Because it has a low bandwidth compared to the
switching frequency, the output filter necessarily limits the
system transient response. The output capacitor must
supply or sink load current while the current in the output
inductors increases or decreases to meet the demand.
ΔV
. This places an upper limit on inductance.
MAX
Equation 38 gives the upper limit on L for the cases when
the trailing edge of the current transient causes a greater
output-voltage deviation than the leading edge. Equation 39
addresses the leading edge. Normally, the trailing edge
dictates the selection of L because duty cycles are usually
less than 50%. Nevertheless, both inequalities should be
evaluated, and L should be selected based on the lower of
the two results. In each equation, L is the per-channel
inductance, C is the total output capacitance, and N is the
number of active channels.
In high-speed converters, the output capacitor bank is
usually the most costly (and often the largest) part of the
circuit. Output filter design begins with minimizing the cost of
this part of the circuit. The critical load parameters in
choosing the output capacitors are the maximum size of the
load step, ΔI; the load-current slew rate, di/dt; and the
maximum allowable output-voltage deviation under transient
loading, ΔV
. Capacitors are characterized according to
2NCV
O
MAX
(EQ. 38)
L ≤ --------------------- ΔV
– ΔI(ESR)
MAX
2
their capacitance, ESR, and ESL (equivalent series
inductance).
(
)
ΔI
(EQ. 39)
(
)
)
1.25 NC
⎛
⎝
⎞
– V
O
L ≤ ------------------------- ΔV
– ΔI(ESR)
V
At the beginning of the load transient, the output capacitors
supply all of the transient current. The output voltage will
initially deviate by an amount approximated by the voltage
drop across the ESL. As the load current increases, the
voltage drop across the ESR increases linearly until the load
current reaches its final value. The capacitors selected must
have sufficiently low ESL and ESR so that the total output-
voltage deviation is less than the allowable maximum.
Neglecting the contribution of inductor current and regulator
response, the output voltage initially deviates by an amount:
MAX
IN
2
⎠
(
ΔI
Input Supply Voltage Selection
The VCC input of the ISL6326B can be connected either
directly to a +5V supply or through a current limiting resistor
to a +12V supply. An integrated 5.8V shunt regulator
maintains the voltage on the VCC pin when a +12V supply is
used. A 300Ω resistor is suggested for limiting the current
into the VCC pin to a worst-case maximum of approximately
25mA.
di
(EQ. 36)
ΔV ≈ (ESL) ---- + (ESR) ΔI
Switching Frequency Selection
dt
There are a number of variables to consider when choosing
the switching frequency, as there are considerable effects on
the upper-MOSFET loss calculation. These effects are
outlined in MOSFETs, and they establish the upper limit for
the switching frequency. The lower limit is established by the
requirement for fast transient response and small output-
The filter capacitor must have sufficiently low ESL and ESR
so that ΔV < ΔV
.
MAX
Most capacitor solutions rely on a mixture of high-frequency
capacitors with relatively low capacitance in combination
FN9286.0
April 21, 2006
27
ISL6326B
voltage ripple as outlined in Output Filter Design. Choose the
lowest switching frequency that allows the regulator to meet
the transient-response requirements.
support the RMS current calculated. The voltage rating of
the capacitors should also be at least 1.25 times greater
than the maximum input voltage.
Figures 18 and 19 provide the same input RMS current
information for three and four phase designs respectively.
Use the same approach to selecting the bulk capacitor type
and number as described above.
Input Capacitor Selection
The input capacitors are responsible for sourcing the AC
component of the input current flowing into the upper
MOSFETs. Their RMS current capacity must be sufficient to
handle the AC component of the current drawn by the upper
MOSFETs which is related to duty cycle and the number of
active phases.
Low capacitance, high-frequency ceramic capacitors are
needed in addition to the bulk capacitors to suppress leading
and falling edge voltage spikes. The result from the high
current slew rates produced by the upper MOSFETs turn on
and off. Select low ESL ceramic capacitors and place one as
close as possible to each upper MOSFET drain to minimize
board parasitic impedances and maximize suppression.
0.3
0.2
0.1
0.3
I
I
= 0
= 0.25 I
I
I
= 0.5 I
O
L,PP
L,PP
L,PP
L,PP
= 0.75 I
O
O
0.2
0.1
0
I
I
I
= 0
L,PP
L,PP
L,PP
= 0.5 I
O
= 0.75 I
O
0
0
0.2
0.4
0.6
0.8
1.0
DUTY CYCLE (V /V
)
IN
O
FIGURE 17. NORMALIZED INPUT-CAPACITOR RMS CURRENT
vs DUTY CYCLE FOR 2-PHASE CONVERTER
0
0.2
0.4
0.6
0.8
1.0
DUTY CYCLE (V
V
)
O/ IN
0.3
I
I
= 0
I
I
= 0.5 I
O
L,PP
L,PP
FIGURE 19. NORMALIZED INPUT-CAPACITOR RMS CURRENT
vs DUTY CYCLE FOR 4-PHASE CONVERTER
= 0.25 I
= 0.75 I
O
L,PP
O
L,PP
MULTIPHASE RMS IMPROVEMENT
0.2
0.1
0
Figure 20 is provided as a reference to demonstrate the
dramatic reductions in input-capacitor RMS current upon the
implementation of the multiphase topology. For example,
compare the input RMS current requirements of a two-phase
converter versus that of a single phase. Assume both
converters have a duty cycle of 0.25, maximum sustained
output current of 40A, and a ratio of I
to I of 0.5. The
L,PP
O
single phase converter would require 17.3Arms current
capacity while the two-phase converter would only require
10.9Arms. The advantages become even more pronounced
when output current is increased and additional phases are
added to keep the component cost down relative to the
single phase approach.
0
0.2
0.4
0.6
0.8
1.0
DUTY CYCLE (V
V
)
O/ IN
FIGURE 18. NORMALIZED INPUT-CAPACITOR RMS CURRENT
vs DUTY CYCLE FOR 3-PHASE CONVERTER
For a two phase design, use Figure 17 to determine the
input-capacitor RMS current requirement given the duty
cycle, maximum sustained output current (I ), and the ratio
O
of the per-phase peak-to-peak inductor current (I
) to I .
L,PP
O
Select a bulk capacitor with a ripple current rating which will
minimize the total number of input capacitors required to
FN9286.0
April 21, 2006
28
ISL6326B
0.6
0.4
0.2
0
I
I
I
= 0
= 0.5 I
= 0.75 I
L,PP
L,PP
L,PP
O
O
0
0.2
0.4
0.6
0.8
1.0
DUTY CYCLE (V
V
)
O/ IN
FIGURE 20. NORMALIZED INPUT-CAPACITOR RMS
CURRENT vs DUTY CYCLE FOR SINGLE-PHASE
CONVERTER
Layout Considerations
The following layout strategies are intended to minimize the
impact of board parasitic impedances on converter
performance and to optimize the heat-dissipating capabilities
of the printed-circuit board. These sections highlight some
important practices which should not be overlooked during the
layout process.
Component Placement
Within the allotted implementation area, orient the switching
components first. The switching components are the most
critical because they carry large amounts of energy and tend
to generate high levels of noise. Switching component
placement should take into account power dissipation. Align
the output inductors and MOSFETs such that space between
the components is minimized while creating the PHASE
plane. Place the Intersil MOSFET driver IC as close as
possible to the MOSFETs they control to reduce the parasitic
impedances due to trace length between critical driver input
and output signals. If possible, duplicate the same
placement of these components for each phase.
Next, place the input and output capacitors. Position one
high-frequency ceramic input capacitor next to each upper
MOSFET drain. Place the bulk input capacitors as close to
the upper MOSFET drains as dictated by the component
size and dimensions. Long distances between input
capacitors and MOSFET drains result in too much trace
inductance and a reduction in capacitor performance. Locate
the output capacitors between the inductors and the load,
while keeping them in close proximity to the microprocessor
socket.
FN9286.0
April 21, 2006
29
ISL6326B
Quad Flat No-Lead Plastic Package (QFN)
Micro Lead Frame Plastic Package (MLFP)
L40.6x6
40 LEAD QUAD FLAT NO-LEAD PLASTIC PACKAGE
(COMPLIANT TO JEDEC MO-220VJJD-2 ISSUE C)
2X
0.15
C A
D
MILLIMETERS
A
9
SYMBOL
MIN
NOMINAL
MAX
1.00
0.05
1.00
NOTES
D/2
A
A1
A2
A3
b
0.80
0.90
-
D1
-
-
-
-
D1/2
2X
-
9
N
0.15 C
B
6
0.20 REF
9
INDEX
AREA
1
2
3
E1/2
E/2
9
0.18
3.95
3.95
0.23
0.30
4.25
4.25
5, 8
E1
D
6.00 BSC
-
E
B
D1
D2
E
5.75 BSC
9
2X
4.10
7, 8
0.15 C
B
6.00 BSC
-
2X
TOP VIEW
0.15 C
A
E1
E2
e
5.75 BSC
9
4.10
7, 8
0
A2
4X
C
A
/ /
0.10 C
0.08 C
0.50 BSC
-
k
0.25
0.30
-
-
0.40
-
-
-
L
0.50
0.15
8
SEATING PLANE
A1
A3
SIDE VIEW
9
L1
N
10
5
NX b
40
10
10
-
2
0.10 M C A B
4X P
Nd
Ne
P
3
D2
D2
8
7
3
NX k
(DATUM B)
-
-
0.60
12
9
2
N
θ
-
9
4X P
1
Rev. 1 10/02
(DATUM A)
2
3
(Ne-1)Xe
REF.
NOTES:
E2
6
1. Dimensioning and tolerancing conform to ASME Y14.5-1994.
2. N is the number of terminals.
INDEX
AREA
7
8
E2/2
NX L
8
3. Nd and Ne refer to the number of terminals on each D and E.
4. All dimensions are in millimeters. Angles are in degrees.
N
e
9
(Nd-1)Xe
REF.
CORNER
OPTION 4X
5. Dimension b applies to the metallized terminal and is measured
between 0.15mm and 0.30mm from the terminal tip.
BOTTOM VIEW
6. The configuration of the pin #1 identifier is optional, but must be
located within the zone indicated. The pin #1 identifier may be
either a mold or mark feature.
A1
NX b
5
7. Dimensions D2 and E2 are for the exposed pads which provide
improved electrical and thermal performance.
SECTION "C-C"
C
L
8. Nominal dimensionsare provided toassistwith PCBLandPattern
Design efforts, see Intersil Technical Brief TB389.
C
L
9. Features and dimensions A2, A3, D1, E1, P & θ are present when
Anvil singulation method is used and not present for saw
singulation.
L
L
10
10
L1
L1
10. Depending on the method of lead termination at the edge of the
package, a maximum 0.15mm pull back (L1) maybe present. L
minus L1 to be equal to or greater than 0.3mm.
e
e
C
C
TERMINAL TIP
FOR ODD TERMINAL/SIDE
FOR EVEN TERMINAL/SIDE
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
FN9286.0
April 21, 2006
30
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