MAXIM MAX1937, MAX1938, MAX1939 User Manual
General Description
The MAX1937/MAX1938/MAX1939 comprise a family of
synchronous, two-phase, step-down controllers capable
of delivering load currents up to 60A. The controllers utilize Quick-PWM™ control architecture in conjunction with
active load-current voltage positioning. Quick-PWM control provides instantaneous load-step response, while
programmable voltage positioning allows the converter
to utilize full transient regulation limits, reducing the output capacitance requirement. The two phases operate
180° out-of-phase with an effective 500kHz switching frequency, thus reducing input and output current ripple, as
well as reducing input filter capacitor requirements.
The MAX1937/MAX1938/MAX1939 are compliant with
AMD Hammer, Intel®‚ Voltage-Regulator Module (VRM)
9.0/9.1, and AMD Athlon™ Mobile VID code specifications (see Table 1 for VID codes). The internal DAC provides ultra-high accuracy of ±0.75%. A controlled VID
voltage transition is implemented to minimize both
undervoltage and overvoltage overshoot during VID
input change.
Remote sensing is available for high output-voltage
accuracy. The MOSFET switches are driven by a 6V
gate-drive circuit to minimize switching and crossover
conduction losses to achieve efficiency as high as
90%. The MAX1937/MAX1938/MAX1939 feature cycleby-cycle current limit to ensure that the current limit is
not exceeded. Crowbar protection is available to protect against output overvoltage.
Applications
Notebook and Desktop Computers
Servers and Workstations
Blade Servers
High-End Switches
High-End Routers
Macro Base Stations
Features
♦ ±0.75% Output Voltage Accuracy
♦ Instant Load-Transient Response
♦ Up to 90% Efficiency Eliminates Heatsinks
♦ Up to 60A Output Current
♦ 8V to 24V Input Range
♦ User-Programmable Voltage Positioning
♦ Controlled VID Voltage Transition
♦ 500kHz Effective Switching Frequency
♦ MAX1937: AMD Hammer Compatible
♦ MAX1938: Intel VRM 9.0/9.1 Compatible
♦ MAX1939: AMD Athlon Mobile Compatible
♦ Soft-Start
♦ Power-Good (PWRGD) Output
♦ Cycle-by-Cycle Current Limit
♦ Output Overvoltage Protection (OVP)
♦ R
DS(ON)
or R
SENSE
Current Sensing
♦ Remote Voltage Sensing
♦ 28-Pin QSOP Package
MAX1937/MAX1938/MAX1939
Two-Phase Desktop CPU Core Supply
Controllers with Controlled VID Change
________________________________________________________________ Maxim Integrated Products 1
28
27
26
25
24
23
22
21
20
19
18
17
16
15
1
2
3
4
5
6
7
8
9
10
11
12
13
14
V
CC
BST1
DH1
LX1
CS1
DL1
PWRGD
VLG
PGND
DL2
CS2
LX2
DH2
BST2
FB
EN
REF
GNDS
GND
ILIM
V
DD
VPOS
VID4
VID3
VID2
TIME
VID1
VID0
QSOP
TOP VIEW
MAX1937
MAX1938
MAX1939
Pin Configuration
Ordering Information
19-2498; Rev 1; 10/02
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.
EVALUATION KIT
AVAILABLE
PART TEMP RANGE PIN-PACKAGE
MAX1937EEI -40°C to +85°C 28 QSOP
MAX1938EEI -40°C to +85°C 28 QSOP
MAX1939EEI -40°C to +85°C 28 QSOP
Quick-PWM is a trademark of Maxim Integrated Products, Inc.
Athlon is a trademark of Advanced Micro Devices, Inc.
Intel is a registered trademark of Intel Corp.
Typical Application Circuits and Functional Diagram appear
at end of data sheet.
MAX1937/MAX1938/MAX1939
Two-Phase Desktop CPU Core Supply
Controllers with Controlled VID Change
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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.
VCCto GND............................................................-0.3V to +28V
V
DD
, PWRGD, ILIM, FB to GND ...............................-0.3V to +6V
EN, GNDS, VPOS, REF, VID_,
TIME to GND ............................................0.3V to V
VDD
+ 0.3V
PGND to GND .......................................................-0.3V to +0.3V
CS1, CS2 to GND ......................................................-2V to +28V
VLG to GND..............................................................-0.3V to +7V
BST1, BST2 to GND ...............................................-0.3V to +35V
LX1 to BST1..............................................................-7V to +0.3V
LX2 to BST2..............................................................-7V to +0.3V
DH1 to LX1.................................................-0.3V to V
BST1
+ 0.3V
DH2 to LX2.................................................-0.3V to V
BST2
+ 0.3V
DL1, DL2 to PGND ......................................-0.3V to V
VLG
+ 0.3V
Continuous Power Dissipation (T
A
= +70°C)
28-Pin QSOP (derate 20.8mW/°C above +70°C)......860.2mW
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
ELECTRICAL CHARACTERISTICS
(VCC= 12V, VEN= V
VDD
= 5V, PGND = GNDS = GND = 0, VID_ = GND, C
VPOS
= 47pF, C
REF
= 0.1µF, V
ILIM
= 1V, TA= 0°C to
+85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER CONDITIONS
UNITS
GENERAL
MAX1937 6 24
V
CC
Operating Range
MAX1938/MAX1939 8 24
V
V
DD
Operating Range 4.5 5 5.5 V
VLG Operating Range V
VLG
> V
VDD
4.5 6.5 V
V
CC
Operating Supply Current FB above threshold (no switching) 20 40 µA
V
DD
Operating Supply Current FB above threshold (no switching) 1.4 2.5 mA
VLG Operating Supply Current FB above threshold (no switching) 20 60 µA
V
CC
Shutdown Current EN = GND <1 5 µA
V
DD
Shutdown Current EN = GND, VID_ not connected 50
µA
VLG Shutdown Current EN = GND <1 5 µA
TIME Output Voltage
V
ILIM Input Bias V
ILIM
= 1.5V
nA
VPOS Output Voltage
CS_= GND, VPOS connected to REF through a 75kΩ
resistor
2.0
V
REFERENCE
Reference Voltage -50µA ≤ I
REF
≤ 50µA
V
SOFT-START
MAX1937 1.1 5.5
MAX1938 1.5 6.2 Ramp Period
MAX1939 1.3 6.5
ms
Soft-Start Voltage Step 25 mV
ERROR AMPLIFIER
FB Input Resistance Resistance from FB to GND
kΩ
GNDS Input Bias Current -5 +5 µA
Output Regulation Voltage
Accuracy
%
MIN TYP MAX
1.96 2.00 2.04
-250
1.96
100
+250
2.04
1.987 2.000 2.013
180
-0.75
+0.75
MAX1937/MAX1938/MAX1939
Two-Phase Desktop CPU Core Supply
Controllers with Controlled VID Change
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VCC= 12V, VEN= V
VDD
= 5V, PGND = GNDS = GND = 0, VID_ = GND, C
VPOS
= 47pF, C
REF
= 0.1µF, V
ILIM
= 1V, TA= 0°C to
+85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER CONDITIONS
UNITS
FAULT PROTECTION
V
DD
Undervoltage Lockout
(UVLO) Threshold
Rising or falling V
DD
V
V
DD
UVLO Hysteresis 80 mV
VLG UVLO Threshold Rising or falling VLG
V
VLG UVLO Hysteresis 40 mV
Thermal Shutdown Rising temperature, typical hysteresis = 15°C
°C
Rising edge
Reference UVLO Threshold
Falling edge
V
MAX1937/MAX1938
Output Overvoltage Fault
Threshold
MAX1939
V
Output UVLO Threshold
Rising and falling percentage of the nominal
regulation voltage
65 70 75 %
CURRENT LIMIT
PGND to CS_, V
ILIM
= 1.5V
PGND to CS_, V
ILIM
= 1V 90
Current-Limit Threshold
PGND to CS_, V
ILIM
= 0.5V 45 50 55
mV
CS Input Offset Voltage CS_ = GND -3 +3 mV
CS_ Input Bias Current CS_ = GND -5 +5 µA
VOLTAGE POSITIONING
VPOS Input Offset Voltage -3 +3 mV
VPOS Gain
%/V
VPOS Gain
From CS1, CS2 to FB; V
CS1
, V
CS2
= +13mV, -113mV;
R
VPOS
= 75kΩ
68 75 82 %/V
TIMER AND DRIVERS
On-Time LX1 = LX2 = CS1 = CS2 = GND, V
FB
= 1.5V
ns
Minimum Off-Time DH1 low to DH2 high, and DH2 low to DH1 high
ns
MAX1937/MAX1938 60
DH_ low to DL_ high
MAX1939
60
MAX1937/MAX1938 85
Break-Before-Make Time
DL_ low to DH_ high
MAX1939
70
ns
MIN TYP MAX
4.00 4.25 4.45
4.00 4.25 4.45
160
1.600
1.584
Rising and falling
1.97 2.00 2.03
2.215 2.250 2.285
135 150 165
100 110
From CS_ to FB; V
CS1
, V
= 0, -100mV; R
CS2
VPOS
= 75kΩ 72.5 75.0 77.5
420 525 630
260 325 390
MAX1937/MAX1938/MAX1939
Two-Phase Desktop CPU Core Supply
Controllers with Controlled VID Change
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(VCC= 12V, VEN= V
VDD
= 5V, PGND = GNDS = GND = 0, VID_ = GND, C
VPOS
= 47pF, C
REF
= 0.1µF, V
ILIM
= 1V, TA= 0°C to
+85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER CONDITIONS
DH_ On-Resistance in Low State
V
BST1
= V
BST2
= 6V, LX1 = LX2 = GND 1.5 3.0 Ω
DH_ On-Resistance in High State
V
BST_
= 6V, LX_ = GND 1.5 3.0 Ω
DL_ On-Resistance in Low State
0.5 1.7 Ω
DL_ On-Resistance in High State
1.5 3.0 Ω
BST_ Leakage Current V
BST_
= 30V, V
LX_
= 24V 50 µA
LX_ Leakage Current V
BST_
= 30V, V
LX_
= 24V 50 µA
EN AND VID
Low Level Threshold 0.8 V
High Level Threshold 1.6 V
Pullup Resistance Internally pulled up to V
DD
50
kΩ
PWRGD
PWRGD Upper Trip Level
%
PWRGD Lower Trip Level -15
-10 %
Output Low Level 0.4 V
Output High Leakage 1 µA
CONTROLLED VID CHANGE
R
TIME
= 120kΩ
R
TIME
= 47kΩ
On-the-Fly VID Change Slew
Rate
25mV per step
R
TIME
= 470kΩ
µs
VID_ Change Frequency Range
38
kHz
PWRGD Blanking Time V
VDD
= 4.5V to 5.5V
µs
MIN TYP MAX UNITS
10.0 12.5 15.0
100 200
-12.5
6.17 6.67 7.25
2.35 2.63 2.99
23.5 26.3 29.9
380
125 200 350
MAX1937/MAX1938/MAX1939
Two-Phase Desktop CPU Core Supply
Controllers with Controlled VID Change
_______________________________________________________________________________________ 5
ELECTRICAL CHARACTERISTICS
(V
VCC
= 12V, VEN= V
VDD
= 5V, PGND = GNDS = GND, VID_= GND, C
VPOS
= 47pF, C
REF
= 0.1µF, V
ILIM
= 1V, TA= -40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER CONDITIONS
UNITS
GENERAL
MAX1937 6 24
V
CC
Operating Range
MAX1938/MAX1939 8 24
V
V
DD
Operating Range 4.5 5.5 V
VLG Operating Range V
VLG
≥ V
VDD
4.5 6.5 V
V
CC
Operating Supply Current FB above threshold (no switching) 40 µA
V
DD
Operating Supply Current FB above threshold (no switching) 2.5 mA
VLG Operating Supply Current FB above threshold (no switching) 20 60 µA
V
CC
Shutdown Current EN = GND 5 µA
V
DD
Shutdown Current EN = GND, VID_ not connected
µA
VLG Shutdown Current EN = GND 5 µA
TIME Output Voltage
V
ILIM Input Bias V
ILIM
= 1V
nA
VPOS Output Voltage
CS_ = GND, VPOS connected to REF through a 75kΩ
resistor
V
REFERENCE
Reference Voltage -50µA ≤ I
REF
≤ 50µA
V
SOFT-START
MAX1937 1.1 5.5
MAX1938 1.5 6.6 Ramp Period
MAX1939 1.3 7.0
ms
ERROR AMPLIFIER
GNDS Input Bias Current -5 +5 µA
Output Regulation Voltage
Accuracy
-1 +1 %
FAULT PROTECTION
V
DD
UVLO Threshold Rising or falling V
DD
V
VLG UVLO Threshold Rising or falling VLG
V
MAX1937/MAX1938
Output Overvoltage Fault
Threshold
MAX1939
V
Output UVLO Threshold
Rising and falling percentage of the nominal
regulation voltage
65 75 %
CURRENT LIMIT
PGND to CS_, V
ILIM
= 1.5V
PGND to CS_, V
ILIM
= 1V 90
Current-Limit Threshold
PGND to CS_, V
ILIM
= 0.5V 45 55
mV
MIN TYP MAX
1.96
-250
1.96
1.98
100
2.04
+250
2.04
2.02
Rising and falling
4.00
4.00
1.97
2.215
135
4.45
4.45
2.03
2.285
165
110
MAX1937/MAX1938/MAX1939
Two-Phase Desktop CPU Core Supply
Controllers with Controlled VID Change
6 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(V
VCC
= 12V, VEN= V
VDD
= 5V, PGND = GNDS = GND, VID_= GND, C
VPOS
= 47pF, C
REF
= 0.1µF, V
ILIM
= 1V, TA= -40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER CONDITIONS
UNITS
CS Input Offset Voltage CS_ = GND -5 +5 mV
CS_ Input Bias Current CS_ = GND -5 +5 µA
VOLTAGE POSITIONING
VPOS Input Offset Voltage -5 +5 mV
VPOS Gain
%/V
VPOS Gain
From CS1, CS2 to FB; V
CS1
, V
CS2
= +13mV, -113mV;
R
VPOS
= 75kΩ
68 82 %/V
TIMER AND DRIVERS
On-Time LX1 = LX2 = CS1 = CS2 = GND, V
FB
= 1.5V
ns
Minimum Off-Time DH1 low to DH2 high, and DH2 low to DH1 high
ns
DH_ On-Resistance in Low State
V
BST1
= V
BST2
= 6V, LX1 = LX2 = GND 3 Ω
DH_ On-Resistance in High State
V
BST_
= 6V, LX_ = GND 3 Ω
DL_ On-Resistance in Low State
1.7 Ω
DL_ On-Resistance in High State
3 Ω
BST_ Leakage Current V
BST_
= 30V, V
LX_
= 24V 50 µA
LX_ Leakage Current V
BST_
= 30V, V
LX_
= 24V 50 µA
EN AND VID_
Low Level Threshold 0.8 V
High Level Threshold 1.6 V
Pullup Resistance Internally pulled up to V
DD
50
kΩ
PWRGD
PWRGD Upper Trip Level 10 15 %
PWRGD Lower Trip Level -15 -10 %
Output Low Level 0.4 V
Output High Leakage 1 µA
CONTROLLED VID CHANGE
R
TIME
= 120kΩ
R
TIME
= 47kΩ
On-the-Fly VID Change Slew
Rate
25mV per step
R
TIME
= 470kΩ
µs
VID_ Change Frequency Range
38
kHz
PWRGD Blanking Time V
VDD
= 4.5V to 5.5V
µs
Note 1: Specifications to -40°C are guaranteed by design and not production tested.
MIN TYP MAX
From CS_ to FB; V
CS1
, V
= 0, -100mV; R
CS2
= 75kΩ 72.5
VPOS
420
260
77.5
630
390
200
6.17
2.35
23.5
7.25
2.99
29.9
380
125
350
MAX1937/MAX1938/MAX1939
Two-Phase Desktop CPU Core Supply
Controllers with Controlled VID Change
_______________________________________________________________________________________ 7
EFFICIENCY vs. LOAD CURRENT
AT 1.45V OUTPUT
MAX1937 toc01
LOAD CURRENT (A)
EFFICIENCY (%)
10
60
70
80
90
50
1 100
VIN = 8V
VIN = 14V
V
IN
= 12V
V
OUT
= 1.45V
50
60
70
80
90
1 10 100
EFFICIENCY vs. LOAD CURRENT
AT 1.85V OUTPUT
MAX1937 toc02
LOAD CURRENT (A)
EFFICIENCY (%)
VIN = 12V
V
IN
= 14V
V
OUT
= 1.85V
V
IN
= 8V
FREQUENCY vs. LOAD CURRENT
MAX1937 toc03
LOAD CURRENT (A)
FREQUENCY (kHz)
5040302010
50
100
150
200
250
300
350
0
060
VIN = 12V
V
OUT
= 1.45V
FREQUENCY vs. INPUT VOLTAGE
MAX1937 toc04
INPUT VOLTAGE (V)
FREQUENCY (kHz)
131211109
175
200
225
250
275
300
325
150
814
I
LOAD
= 46A
V
OUT
= 1.45V
I
LOAD
= 1A
FREQUENCY vs. TEMPERATURE
MAX1937 toc05
TEMPERATURE (°C)
FREQUENCY (kHz)
8060-20 0 20 40
225
230
235
240
245
250
255
260
220
-40 100
VIN = 12V
V
OUT
= 1.45V
I
LOAD
= 10A
VCC INPUT CURRENT
vs. INPUT VOLTAGE
MAX1937 toc06
INPUT VOLTAGE (V)
V
CC
INPUT CURRENT (μA)
131211109
5
10
15
20
25
0
814
V
OUT
= 1.45V
VDD CURRENT vs. VDD VOLTAGE
MAX1937 toc07
V
DD
VOLTAGE (V)
V
DD
CURRENT (mA)
5.35.14.94.7
1.55
1.60
1.65
1.70
1.75
1.80
1.50
4.5 5.5
Typical Operating Characteristics
(VIN= 12V, V
OUT
= 1.45V, TA= +25°C, unless otherwise noted.)
MAX1937/MAX1938/MAX1939
Two-Phase Desktop CPU Core Supply
Controllers with Controlled VID Change
8 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(VIN= 12V, V
OUT
= 1.45V, TA= +25°C, unless otherwise noted.)
CURRENT SHARING
MAX1937 toc10
LOAD CURRENT (A)
INDUCTOR CURRENTS (A)
40302010
0
5
10
15
20
25
30
-5
050
VIN = 12V
V
OUT
= 1.45V
T
A
= +25°C
CURRENT SHARING
MAX1937 toc11
LOAD CURRENT (A)
INDUCTOR CURRENTS (A)
40302010
0
5
10
15
20
25
30
-5
050
VIN = 12V
V
OUT
= 1.45V
T
A
= +80°C
V
IN
= 12V
V
OUT
= 1.45V
I
OUT
= 0A
0A
OUTPUT INDUCTOR
CURRENTS:
10A/div
OUTPUT RIPPLE
VOLTAGE:
20mV/div
2μs/div
MAX1937 toc12
INDUCTOR CURRENT WAVEFORMS
WITH 0A LOAD
V
IN
= 12V
V
OUT
= 1.45V
I
OUT
= 40A
OUTPUT INDUCTOR
CURRENTS:
10A/div
OUTPUT RIPPLE
VOLTAGE:
20mV/div
2μs/div
MAX1937 toc13
INDUCTOR CURRENT WAVEFORMS
WITH 40A LOAD
0A
OUTPUT VOLTAGE vs. LOAD CURRENT
AT 1.45V OUTPUT
MAX1937 toc09
LOAD CURRENT (A)
V
OUT
40302010
1.375
1.400
1.425
1.450
1.350
050
R
VPOS
= 90.9k
Ω
VIN = 12V
R
VPOS
= 120k
Ω
VDD CURRENT vs. VDD VOLTAGE
IN SHUTDOWN
MAX1937 toc08
VDD VOLTAGE (V)
V
DD
CURRENT (mA)
5.35.14.94.7
35
40
45
50
55
65
60
70
30
4.5 5.5
VID_ NOT CONNECTED
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