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19-2855; Rev 2; 4/05
2- to 8-Phase VRM 10/9.1 PWM Controllers
with Precise Current Sharing and Fast Voltage
Positioning
General Description
The MAX8525 (VRM 10/VRD 10)/MAX8524 (VRM 9.1/
VRD 9.1) current-mode step-down controllers, the
MAX8523 high-speed, dual-phase MOSFET gate driver,
and the MAX8552 wide-input, single-phase MOSFET
gate driver provide flexible, low-cost, low-voltage CPU
core supplies. The MAX8523 and MAX8552 high-speed,
high-current gate drivers allow operation at high switch-
ing frequencies to reduce external component size and
cost for small-footprint, low-profile designs. Pin-selec-
table 2-, 3-, and 4-phase operation and master-slave 6-
and 8-phase operation provide output-current scalability
for servers, workstations, desktops, desk notes, and net-
working applications.
The switching frequency of the MAX8524/MAX8525 is
adjustable from 150kHz to 1.2MHz, permitting loop
bandwidths of up to 200kHz. Peak current-mode con-
trol provides fast transient response and reduces cost.
A proprietary current-sharing scheme reduces current
imbalance between phases to less than 5% at full load.
The MAX8524/MAX8525 offer 0.4% initial accuracy and
remote-sense functionality. Both controllers also feature
programmable no-load offset and output-voltage posi-
tioning to adjust the output voltage as a function of the
output current. The fast-active voltage positioning further
reduces bulk output capacitors and cost.
Current-mode control also simplifies compensation with
a variety of capacitors by eliminating the output-filter
double pole associated with voltage-mode controllers.
Both devices are compatible with electrolytic, tantalum,
polymer, and ceramic capacitors. Output current sens-
ing eliminates issues associated with controllers that
use high-side current sense and ensure stable and jit-
ter-free operation. Temperature-compensated, lossless
inductor current sense eliminates the need for a cur-
rent-sense resistor and further reduces cost, while
maintaining voltage-positioning accuracy and reducing
power dissipation.
The MAX8525 features control VID voltage transition for
dynamic VID changes and eliminate both undervoltage
and overvoltage overshoot. The PWRGD signal is accu-
rate during VID code changes for the MAX8525 to
avoid any false fault signal.
Adjustable foldback current-limit and overvoltage pro-
tection provide for a robust design.
♦
♦
♦
♦
Features
VRD/VRM 10 (MAX8525)
VRD/VRM 9.1 (MAX8524)
Fastest Load-Transient Response
Rapid-Active Average Current Sensing
Better than 5% Current Balance
Fastest Voltage Positioning
±0.4% Initial Output-Voltage Accuracy
Pin-Selectable 2-/3-/4-Phase Operation
Master-Slave 6-/8-Phase Operation
Differential Remote Voltage Sensing
Dynamic VID Change (MAX8525)
Adjustable, Foldback Current Limit
Soft-Start and Soft-Stop
Power-Good Output
150kHz to 1.2MHz Switching Frequency per Phase
28-Lead QSOP Package
MAX8524/MAX8525
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
Ordering Information
PART
MAX8524EEI
MAX8524EEI+
MAX8525EEI
MAX8525EEI+
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 QSOP
28 QSOP
28 QSOP
28 QSOP
+Denotes
lead-free package.
Pin Configurations
TOP VIEW
PWM3 1
PWM1 2
CS1+ 3
CS1_3- 4
CS3+ 5
V
CC
6
GND 7
COMP 8
REF 9
ILIM 10
OSC 11
PWRGD 12
CLKO 13
CLKI 14
28 PWM2
27 PWM4
26 CS4+
25 CS2_4-
24 CS2+
MAX8525
23 RS+
22 RS-
21 EN
20 VID4
19 VID3
18 VID2
17 VID1
16 VID0
15 VID5
Applications
Servers, Workstations
Desktop Computers
Desk Notes and LCD PCs
Voltage-Regulator Modules
High-End Switches and Routers
QSOP
Pin Configurations continued at end of data sheet.
Functional Diagram appears at end of data sheet.
1
________________________________________________________________
Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
2- to 8-Phase VRM 10/9.1 PWM Controllers
with Precise Current Sharing and Fast Voltage
Positioning
MAX8524/MAX8525
ABSOLUTE MAXIMUM RATINGS
REF, COMP, VID0 to VID5, OSC, CLKI,
CLKO to GND ..........................................-0.3V to V
CC
+ 0.3V
RS+, RS-, ILIM to GND .................................-0.3V to V
CC
+ 0.3V
PWM_ to GND...............................................-0.3V to V
CC
+ 0.3V
EN, PWRGD, V
CC
to GND ........................................-0.3V to +6V
CS1_3-, CS2_4-, CS_+ to GND ....................-0.3V to V
CC
+ 0.3V
Continuous Power Dissipation (T
A
= +70°C)
28-Pin QSOP (derate 10.8mW/°C above +70°C).........860mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
CC
= 5V, VID_ = high, ILIM = 1.5V, EN = open, RS- = GND = 0V, CLKI = open, CLKO = open, R
OSC
= 95.3kΩ to GND, PWRGD =
100kΩ to V
CC
, PWM_ = open, COMP = 1V, CS_+ = 1.1V, CS1_3- = CS2_4- = RS+ = 1.1V,
T
A
= 0°C to +85°C,
unless otherwise
noted.)
PARAMETER
GENERAL
V
CC
Operating Range
V
CC
UVLO Trip Level
V
CC
Shutdown Supply Current
V
CC
Standby Supply Current
V
CC
Operating Supply Current
Thermal Shutdown
REFERENCE
Reference Voltage
Reference Load Regulation
Reference Line Regulation
Reference UVLO Trip Level
SOFT-START
Soft-Start Step Size
Soft-Start Time per Step
VOLTAGE REGULATION
RS+ Input Bias Current
RS- Input Bias Current
V
OUT
Initial Accuracy
V
OUT
Droop Accuracy
COMP Output Current
GMV Amplifier Transconductance
GMV Amplifier Gain-Bandwidth
Product
V
RS+
= 1.1V
V
RS-
= 0.2V
VID_ = 1.1V, T
A
= +25°C
VID_ = 1.1V
(CS_+) = 1.125V
(VO+) - (RS+) = 200mV
-0.4
-0.6
±5
385
2
5
0.1
0.1
1
1
+0.4
+0.6
µA
µA
%
%
µA
mS
MHz
Soft-start counts from EN rising (Note 1)
17
12.5
20
23
mV
µs
I
REF
= 200µA
100µA < I
REF
< 500µA
4.5V < V
CC
< 5.5V
Rising edge, has 80mV typical hysteresis
-0.05
1.74
1.84
2.0
- 0.4%
2.0
2.0
+ 0.4%
-0.05
+0.05
1.95
V
%
%
V
Rising
Hysteresis
V
CC
< 3.75V, VID_ = GND
EN = 0V, V
CC
= 5.5V
RS+ = 1.2V (no switching), set VID code for 1.100V
Rising temperature, typical hysteresis = 15°C
4.5
4.0
4.25
270
0.7
13
13
165
3
20
20
5.5
4.5
V
V
mV
mA
mA
mA
°C
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
2- to 8-Phase VRM 10/9.1 PWM Controllers
with Precise Current Sharing and Fast Voltage
Positioning
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 5V, VID_ = high, ILIM = 1.5V, EN = open, RS- = GND = 0V, CLKI = open, CLKO = open, R
OSC
= 95.3kΩ to GND, PWRGD =
100kΩ to V
CC
, PWM_ = open, COMP = 1V, CS_+ = 1.1V, CS1_3- = CS2_4- = RS+ = 1.1V,
T
A
= 0°C to +85°C,
unless otherwise
noted.)
PARAMETER
CURRENT-SENSE AMPLIFIERS
CS_+, CS_- Input Bias Current
Average Current-Limit Trip Level
Accuracy
ILIM Input Bias Current
ILIM Default Program Level
Peak Current-Limit Delay Time
OSCILLATOR
Oscillator Frequency Accuracy
Switching Frequency Range
(per Phase)
Slave-Mode CLKI/Set Frequency
Ratio
Maximum CLKO Duty-Cycle
Skew
LOGIC INPUTS (EN)
Input Low Level
Input High Level
Input Pullup Level
Input Pullup Resistance
LOGIC INPUTS (CLKI)
Input Low Level
Input High Level
Input Pulldown Level
Input Pulldown Resistance
Input Low Level
Input High Level
Input Pullup Level
Input Pullup Resistance
Input Low Level
Input High Level
PWRGD OUTPUT
Output Low Level
Output High Leakage
PWRGD Blanking Time
I
PWRGD
= 4mA
V
PWRGD
= 5.5V
From EN rising, tracks CLKO
3
0.4
1
5
V
µA
ms
Internal pullup resistance
V
CC
= 4.5V to 5.5V
V
CC
= 4.5V to 5.5V
0.8
10
MAX8525 LOGIC INPUTS (VID0–VID5)
0.4
V
V
V
CC
= 4.5V to 5.5V
V
CC
= 4.5V to 5.5V
Internal pulldown
Internal pulldown
V
CC
= 4.5V to 5.5V
V
CC
= 4.5V to 5.5V
1.6
V
CC
15
20
50
3.6
GND
100
200
0.8
1.2
V
V
V
kΩ
V
V
V
kΩ
V
CC
= 4.5V to 5.5V
V
CC
= 4.5V to 5.5V
Internal pullup
Internal pullup
50
2.8
V
CC
100
200
0.8
V
V
V
kΩ
CLKO load < 50pF and R
OSC
= 40.2kΩ
150
0.8
2
10
1200
4.0
%
%
kHz
CS_+ = CS_- = 2V, RS+ = 0V
V
ILIM
= 1.5V, T
A
= +85°C
V
ILIM
= 1.5V
V
ILIM
≥
V
CC
- 0.2V
-10
0.01
1
20
0.2
5
+10
1
µA
%
µA
V
ns
CONDITIONS
MIN
TYP
MAX
UNITS
MAX8524/MAX8525
MAX8524 LOGIC INPUTS (VID0–VID4)
_______________________________________________________________________________________
3
2- to 8-Phase VRM 10/9.1 PWM Controllers
with Precise Current Sharing and Fast Voltage
Positioning
MAX8524/MAX8525
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 5V, VID_ = high, ILIM = 1.5V, EN = open, RS- = GND = 0V, CLKI = open, CLKO = open, R
OSC
= 95.3kΩ to GND, PWRGD =
100kΩ to V
CC
, PWM_ = open, COMP = 1V, CS_+ = 1.1V, CS1_3- = CS2_4- = RS+ = 1.1V,
T
A
= 0°C to +85°C,
unless otherwise
noted.)
PARAMETER
Output rising
PWRGD Upper Threshold
Output falling
Output falling
PWRGD Lower Threshold
Output rising
OVP PROTECTION
MAX8524 output rising
Output Overvoltage Trip
Threshold, OVP Action
MAX8525 output rising
PWM, CKLO OUTPUTS
Output Low Level
Output High Level
Source Current
Sink Current
Rise/Fall Times
PWM Selection Threshold
V
CC
= 4.5V to 5.5V
0.8
I
PWM_
= -5mA
I
PWM_
= +5mA
V
PWM_
= V
CC
- 2V
V
PWM_
= 2V
4.5
0.1
4.9
84
83
10
2.3
3.1
0.4
V
V
mA
mA
ns
V
VID +
0.20
VID +
0.175
VID +
0.25
V
VID +
0.225
VID -
0.175
VID -
0.125
VID +
0.075
VID -
0.250
VID +
0.125
VID -
0.200
V
CONDITIONS
MIN
VID +
0.125
TYP
MAX
VID +
0.175
V
UNITS
ELECTRICAL CHARACTERISTICS
(V
CC
= 5V, VID_ = high, ILIM = 1.5V, EN = open, RS- = GND = 0V, CLKI = open, CLKO = open, R
OSC
= 95.3kΩ to GND, PWRGD =
100kΩ to V
CC
, PWM_ = open, COMP = 1V, CS_+ = 1.1V, CS1_3- = CS2_4- = RS+ = 1.1V,
T
A
= -40°C to +85°C,
unless otherwise
noted.) (Note 2)
PARAMETER
GENERAL
V
CC
Operating Range
V
CC
UVLO Trip Level
V
CC
Shutdown Supply Current
V
CC
Standby Supply Current
V
CC
Operating Supply Current
REFERENCE
Reference Voltage
Reference Load Regulation
Reference Line Regulation
Reference UVLO Trip Level
I
REF
= 200µA
100µA < I
REF
< 500µA
4.5V < V
CC
< 5.5V
Rising edge, has 80mV typical hysteresis
-0.05
1.74
2.0 -
0.5%
2.0 +
0.4%
-0.05
+0.05
1.95
V
%
%
V
Rising, typical hysteresis 270mV
V
CC
< 3.75V, VID_ = high
EN = 0V, V
CC
= 5.5V
RS+ = 1.2V (no switching), set VID code for 1.100V
4.5
4.0
5.5
4.5
3
20
20
V
V
mA
mA
mA
CONDITIONS
MIN
TYP
MAX
UNITS
4
_______________________________________________________________________________________
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