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PDF ISL6554 Data sheet ( Hoja de datos )
| Número de pieza | ISL6554 | |
| Descripción | Microprocessor CORE Voltage Regulator Using Multi-Phase Buck PWM Control Without Programmable Droop | |
| Fabricantes | Intersil Corporation | |
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TM
Data Sheet
ISL6554
November 2001 File Number 9003.1
Microprocessor CORE Voltage Regulator
Using Multi-Phase Buck PWM Control
Without Programmable Droop
The ISL6554 is the first controller in the Intersil Multi-Phase
family without the programmable droop feature. The ISL6554
in combination with the HIP6601A, HIP6602A or HIP6603A
companion gate drivers and Intersil MOSFETs form a
complete solution for high-current, high slew-rate
applications. The ISL6554 regulates output voltage,
balances load currents and provides protective functions for
two to four synchronous-rectified buck-converter channels.
A novel approach to current sensing is used to reduce
overall solution cost. The voltage developed across the lower
MOSFET’s parasitic on-resistance during conduction is
sampled and fed back to the controller. This lossless current-
sensing approach allows the controller to maintain phase-
current balance between the power channels and
overcurrent protection.
A 5-bit DAC allows digital programming of the output voltage
in 25mV steps over a range from 0.95V to 1.70V with a
system accuracy of ±1%. Internal pull ups on each DAC
input make external pull-up resistors unnecessary when
interfacing with open-drain output signals.
The PGOOD signal is held low during Soft-Start until the
output voltage increases to within 4% of the programmed.
When the CORE voltage falls 9% below the programmed
VID level, an undervoltage condition is detected and results
in PGOOD transitioning low.
In the event of an overvoltage condition, The converter shuts
down and turns ON the lower MOSFETs to clamp and
protect the microprocessor. Overcurrent protection reduces
the regulator RMS output current to 41% of the programmed
overcurrent trip value. These features provide monitoring
and protection for the microprocessor and power system.
Features
• Multi-Phase Power Conversion
• Precision Channel Current Balance
- Lossless Current Sampling - Uses rDS(ON)
• Precision CORE Voltage Regulation
- ±1% System Accuracy Over Temperature
- No Programmable Droop
• Microprocessor Voltage Identification Input
- 5-Bit VID Decoder
- 0.95V to 1.70V in 25mV Steps
• Fast Transient Response
• Over Current Protection
• Selection of 2, 3, or 4 Phase Operation
• High Ripple Frequency (80kHz to 2MHz)
Applications
• Power Supply Controller for Intel® Itanium™ Processor
Family
• Voltage Regulator Modules
• Servers and Workstations
Ordering Information
PART NUMBER TEMP. (oC) PACKAGE PKG. NO.
ISL6554CB
0 to 70 20 Ld SOIC M20.3
ISL6554CB-T
20 Ld SOIC Tape and Reel
Pinout
ISL6554 (SOIC)
TOP VIEW
VID4 1
VID3 2
VID2 3
VID1 4
VID0 5
COMP 6
FB 7
FS/DIS 8
GND 9
VSEN 10
20 VCC
19 PGOOD
18 PWM4
17 ISEN4
16 ISEN1
15 PWM1
14 PWM2
13 ISEN2
12 ISEN3
11 PWM3
Intel™ is a trademark of Intel Corporation.
1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a trademark of Intersil Americas Inc.
Copyright © Intersil Americas Inc. 2001. All Rights Reserved
Intel® is a registered trademark of Intel Corporation. Itanium™ is a trademark of Intel Corporation
1 page  
ISL6554
Typical Application - 4 Phase Converter Using HIP6602 Gate Drivers
+5V
FB
VSEN
COMP
VCC
ISEN1
PGOOD
PWM1
VID4
PWM2
VID3
VID2
VID1
ISEN2
MAIN
CONTROL
ISL6554
VID0
FS/DIS
ISEN3
PWM3
PWM4
GND ISEN4
+12V
VCC
BOOT1
VIN = +12V
UGATE1
PHASE1
LGATE1
DUAL
DRIVER
HIP6602
PVCC
+5V
BOOT2
VIN +12V
PWM1
PWM2
UGATE2
PHASE2
LGATE2
GND
+12V
VCC
BOOT3
V IN+12V
UGATE3
PHASE3
LGATE3
DUAL
DRIVER
HIP6602
PVCC
+5V
BOOT4
VIN +12V
PWM3
PWM4
UGATE4
PHASE4
LGATE4
GND
L01
L02
L03
L04
5
+VCORE
5 Page 
ISL6554
RFB RIN Cc
FB COMP
ERROR
AMPLIFIER
-
+
SAWTOOTH
GENERATOR
CORRECTION
+
ISL6554
COMPARATOR
- PWM
+ CIRCUIT
REFERENCE
DAC
D- IFFERENCE
+
CURRENT
SENSING
TO OVER
CURRENT
TRIP
TO OTHER
CHANNELS
COMPARATOR
-
+
-
REFERENCE
AVERAGING
CURRENT
SENSING
FROM
OTHER
CHANNELS
PWM
ISEN
VIN
Q1
L01
HIP6601
Q2
IL
PHASE
RISEN
ONLY ONE OUTPUT
STAGE SHOWN
INDUCTOR
CURRENT(S)
FROM
OTHER
CHANNELS
VCORE
FIGURE 7. SIMPLIFIED FUNCTIONAL BLOCK DIAGRAM SHOWING CURRENT AND VOLTAGE SAMPLING
The nominal current through the RISEN resistor should be
50µA at full output load current, and the nominal trip point for
overcurrent detection is 165% of that value, or 82.5µA.
Therefore, RISEN = IL x rDS(ON) (Q2) / 50µA.
For a full load of 25A per phase, and an rDS(ON) (Q2) of
4mΩ, RISEN = 2kΩ.
The overcurrent trip point would be 165% of 25A, or ~ 41A
per phase. The RISEN value can be adjusted to change the
overcurrent trip point, but it is suggested to stay within ±25%
of nominal.
Current Balancing
The detected currents are also used to balance the phase
currents.
Each phase’s current is compared to the average of all
phase currents, and the difference is used to create an offset
in that phase’s PWM comparator. The offset is in a direction
to reduce the imbalance.
The balancing circuit can not make up for a difference in
rDS(ON) between synchronous rectifiers. If a FET has a higher
rDS(ON), the current through that phase will be reduced.
Figures 8 and 9 show the inductor current of a two phase
system without and with current balancing.
Inductor Current
The inductor current in each phase of a multi-phase Buck
converter has two components. There is a current equal to
the load current divided by the number of phases (ILT / n),
and a sawtooth current, (iPK-PK) resulting from switching.
The sawtooth component is dependent on the size of the
inductors, the switching frequency of each phase, and the
values of the input and output voltage. Ignoring secondary
effects, such as series resistance, the peak to peak value of
the sawtooth current can be described by:
iPK-PK = (VIN x VCORE - VCORE2) / (L x FSW x VIN)
Where: VCORE = DC value of the output or VID voltage
VIN= DC value of the input or supply voltage
L= value of the inductor
FSW= switching frequency
Example: For VCORE= 1.6V,
VIN= 12V,
L= 1.3µH,
FSW= 250kHz,
Then iPK-PK = 4.3A
The inductor, or load current, flows alternately from VIN
through Q1 and from ground through Q2. The ISL6554
samples the on-state voltage drop across each Q2 transistor
to indicate the inductor current in that phase. The voltage
drop is sampled 1/3 of a switching period, i/FSW, after Q1 is
turned OFF and Q2 is turned on. Because of the sawtooth
current component, the sampled current is different from the
average current per phase. Neglecting secondary effects,
the sampled current (ISAMPLE) can be related to the load
current (ILT) by:
ISAMPLE = ILT / n + (VINVCORE -3VCORE2) / (6L x FSW x VIN)
Where:
ILT= total load current
n= the number of channels
Example: Using the previously given conditions, and
For ILT= 100A,
n= 4
Then ISAMPLE = 25.49A
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet ISL6554.PDF ] | |
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