19-1227; Rev 1; 6/97
IT
TION K
VALUA
E
BLE
AVAILA
High-Speed Step-Down Controllers with
Synchronous Rectification for CPU Power
____________________________Features
o
Better than ±1% Output Accuracy Over
Line and Load
o
90% Efficiency
o
Excellent Transient Response
o
Resistor-Programmable Fixed Switching
Frequency from 100kHz to 1MHz
o
Over 35A Output Current
o
Digitally Programmable Output from 1.1V to 3.5V
in 100mV Increments (MAX1624)
o
Resistor-Adjustable Output down to 1.1V
(MAX1625)
o
Remote Sensing
o
Adjustable AC Loop Gain (MAX1624)
o
GlitchCatcher™ Circuit for Fast Load-Transient
Response (MAX1624)
o
Power-Good (PWROK) Output
o
Current-Mode Feedback
o
Digital Soft-Start
o
Strong 2A Gate Drivers
o
Current-Limited Output
_______________General Description
The MAX1624/MAX1625 are ultra-high-performance,
step-down DC-DC controllers for CPU power in high-end
computer systems. Designed for demanding applications
in which output voltage precision and good transient
response are critical for proper operation, they deliver
over 35A from 1.1V to 3.5V with ±1% total accuracy from
a +5V ±10% supply. Excellent dynamic response cor-
rects output transients caused by the latest dynamically
clocked CPUs. These controllers achieve over 90% effi-
ciency by using synchronous rectification. Flying-capaci-
tor bootstrap circuitry drives inexpensive, external
N-channel MOSFETs.
The switching frequency is resistor programmable from
100kHz to 1MHz. High switching frequencies allow the
use of a small surface-mount inductor and decrease out-
put filter capacitor requirements, reducing board area
and system cost.
The MAX1624 is available in a 24-pin SSOP and offers
additional features such as a digitally programmable out-
put in 100mV increments; adjustable transient response;
selectable 0.5%, 1%, or 2% AC load regulation; and gate
drive for a current-boost MOSFET. The MAX1625 is resis-
tor adjustable and comes in a 16-pin narrow SO pack-
age. Other features in both controllers include internal
digital soft-start, a power-good output, and a 3.5V ±1%
reference output. For a similar controller compatible with
the latest Intel V
RM
/V
ID
specification, see the MAX1638*
data sheet.
MAX1624/MAX1625
__________Typical Operating Circuit
INPUT
+5V
V
CC
TO AGND
TO V
DD
V
DD
CSH
________________________Applications
Pentium Pro™, Pentium II™, PowerPC™, Alpha™,
and K6™ Systems
Desktop Computers
LAN Servers
Industrial Computers
GTL Bus Termination
MAX1625
CSL
BST
PWROK
DH
N
OUTPUT
1.1V TO 4.5V
N
______________Ordering Information
PART
MAX1624EAG
MAX1625ESE
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
24 SSOP
16 Narrow SO
FREQ
LX
DL
PGND
CC2
FB
CC1
REF
AGND
(SIMPLIFIED)
Pin Configurations appear at end of data sheet.
*Future
product.
Pentium Pro and Pentium II are trademarks of Intel Corp.
PowerPC is a trademark of IBM Corp.
Alpha is a trademark of Digital Equipment Corp.
K6 is a trademark of Advanced Micro Devices.
GlitchCatcher is a trademark of Maxim Integrated Products.
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
High-Speed Step-Down Controllers with
Synchronous Rectification for CPU Power
MAX1624/MAX1625
ABSOLUTE MAXIMUM RATINGS
V
DD
, V
CC
, PWROK to AGND ......................................-0.3V to 6V
PGND to AGND ..................................................................±0.3V
CSH, CSL to AGND ....................................-0.3V to (V
CC
+ 0.3V)
NDRV, PDRV, DL to PGND.........................-0.3V to (V
DD
+ 0.3V)
REF, CC1, CC2, LG, D0–D4, FREQ,
FB to AGND................................................-0.3V to (V
CC
+ 0.3V)
BST to PGND ............................................................-0.3V to 12V
BST to LX ....................................................................-0.3V to 6V
DH to LX.............................................(LX - 0.3V) to (BST + 0.3V)
Continuous Power Dissipation (T
A
= ±70°C)
24 Pin SSOP (derate 8.00mW/°C above +70°C) ..........640mW
16 Pin Narrow SO (derate 8.70mW/°C above 70°C).....696mW
Operating Temperature Range
MAX162_E_ _.......................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +125°C
Lead Temperature (soldering, 10sec) .............................+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
DD
= V
CC
= D4 = +5V, PGND = AGND = D0–D3 = 0V, R
FREQ
= 33.3kΩ,
T
A
= 0°C to +85°C,
unless otherwise noted.)
PARAMETER
Input Voltage Range
Input Undervoltage Lockout
V
CC
Supply Current
V
DD
Supply Current
Reference Voltage
Reference Load Regulation
Reference Undervoltage Lockout
Reference Short-Circuit Current
FB Accuracy
FB Set Voltage
V
CC
= V
DD
V
CC
rising edge, 1% hysteresis
V
CC
= V
DD
= 5.5V,
FB overdrive = 200mV
Operating mode
Standby mode
CONDITIONS
MIN
4.5
4.0
TYP
MAX
5.5
4.2
2.5
0.3
0.1
3.465
2.7
0.5
T
A
= +25°C to +85°C
T
A
= 0°C to +85°C
T
A
= +25°C to +85°C
T
A
= 0°C to +85°C
LG = GND
AC Load Regulation
(Note 3)
CSH - CSL =
0mV to 80mV
MAX1624
MAX1625
LG = GND
DC Load Regulation
(Note 3)
CSH - CSL =
0mV to 80mV
MAX1624
MAX1625
PWROK Trip Level
PWROK Output Voltage Low
PWROK Output Current High
Switching Frequency
Rising FB, 1% hysteresis with respect to V
REF
Falling FB, 1% hysteresis with respect to V
REF
I
SINK
= 2mA, V
CC
= 4.5V
PWROK = 5.5V
R
FREQ
= 20kΩ
R
FREQ
= 33.3kΩ
R
FREQ
= 200kΩ
2
850
540
85
1000
600
100
-7.5
6.5
LG = REF
LG = V
CC
LG = REF
LG = V
CC
0.5
1
2
1
0.05
0.1
0.2
0.1
-6
8
-4.5
9.5
0.4
1
1150
660
115
%
V
µA
kHz
kHz
%
%
3.5
3.535
10
3.0
4.0
±1
±1.5
±1
±1.5
UNITS
V
V
mA
mA
V
mV
V
mA
%
%
V
CC
= V
DD
= 5.5V, FB overdrive = 200mV,
operating or standby mode
No load
0µA < I
LOAD
< 100µA
Rising edge, 1% hysteresis
V
REF
= 0V
MAX1624, over line
and load (Note 1)
MAX1625, over line
and load (Note 2)
_______________________________________________________________________________________
High-Speed Step-Down Controllers with
Synchronous Rectification for CPU Power
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= V
CC
= D4 = +5V, PGND = AGND = D0–D3 = 0V, R
FREQ
= 33.3kΩ,
T
A
= 0°C to +85°C,
unless otherwise noted.)
PARAMETER
Maximum Duty Cycle
LG Input Voltage
Logic Input Voltage Low
Logic Input Voltage High
D0–D4 Input Current
LG Input Current
CSH, CSL Input Current
FB Input Current
CC1 Output Resistance
CC2 Transconductance
CC2 Clamp Voltage
CC2 Source/Sink Current
DH On-Resistance
DL On-Resistance
DH, DL Source/Sink Current
DH, DL Dead Time
PDRV Trip Level
NDRV Trip Level
PDRV, NDRV Response Time
PDRV, NDRV On-Resistance
PDRV, NDRV Source/Sink Current
PDRV, NDRV Minimum On-Time
Current-Limit Trip Voltage
Soft-Start Time
BST Leakage Current
To full current limit
BST = 12V, LX = 7V, REF = GND
85
With respect to V
REF
,
FB going low
With respect to V
REF
,
FB going high
FB overdrive = 5%
V
DD
= 4.5V
PDRV = NDRV = 2.5V
T
A
= +25°C
T
A
= 0°C to +85°C
T
A
= +25°C
T
A
= 0°C to +85°C
Minimum
Maximum
100mV overdrive
BST - LX = 4.5V
V
DD
= 4.5V
DH = DL = 2.5V
0
-2.75
-3
1.25
1
75
2
0.5
100
100
1536
50
115
5
2
2.4
4
100
0.7
0.7
2
30
-2
-1.25
-1
2.75
3
2
2
MAX1624, CSH = CSL = 1.3V,
D0–D3 = 5V, D4 = 0V
MAX1625, CSH = CSL = 1.1V
FB = 1.1V
10
1
3.0
V
CC
R
FREQ
= 20kΩ
LG = GND (low)
LG = REF (mid)
LG = V
CC
(high)
D0–D4; V
CC
= 5.5V
D0–D4; V
CC
= 4.5V
D0–D4 = 0V, 5V
2.0
±1
4
50
50
±0.1
µA
kΩ
mmho
V
µA
Ω
Ω
A
ns
%
%
ns
Ω
A
ns
mV
1 / f
OSC
µA
3.3
V
CC
- 0.2
0.8
V
V
µA
µA
µA
CONDITIONS
MIN
85
TYP
90
0.2
3.7
V
MAX
UNITS
%
MAX1624/MAX1625
_______________________________________________________________________________________
3
High-Speed Step-Down Controllers with
Synchronous Rectification for CPU Power
MAX1624/MAX1625
ELECTRICAL CHARACTERISTICS
(V
DD
= V
CC
= D4 = +5V, PGND = AGND = D0–D3= 0V, R
FREQ
= 33.3kΩ,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 4)
PARAMETER
Input Voltage Range
Input Undervoltage Lockout
V
CC
Supply Current
V
DD
Supply Current
Reference Voltage
FB Accuracy
FB Set Voltage
PWROK Trip Level
V
CC
= V
DD
V
CC
rising edge, 1% hysteresis
V
CC
= V
DD
= 5.5V,
FB overdrive = 200mV
Operating mode
Standby mode
CONDITIONS
MIN
4.5
3.9
TYP
MAX
5.5
4.3
3
0.4
0.2
3.447
3.5
3.553
±2.5
±2.5
-8
6
800
510
80
84
-6
8
1000
600
100
90
0.7
0.7
70
100
2
2
130
-4
10
1200
690
120
%
Ω
Ω
mV
kHz
UNITS
V
V
mA
mA
mA
V
%
%
%
V
CC
= V
DD
= 5.5V, FB overdrive = 200mV,
operating or standby mode
No load
MAX1624, over line and load
MAX1625
Rising FB, 1% hysteresis with respect to V
REF
Falling FB, 1% hysteresis with respect to V
REF
R
FREQ
= 20kΩ
R
FREQ
= 33.3kΩ
R
FREQ
= 200kΩ
R
FREQ
= 20kΩ
BST - LX = 4.5V
V
DD
= 4.5V
Switching Frequency
Maximum Duty Cycle
DH On-Resistance
DL On-Resistance
Current-Limit Trip Voltage
Note 1:
FB accuracy is 100% tested at FB = 3.5V (code 10000) with V
CC
= V
DD
= 4.5V to 5.5V and CSH - CSL = 0mV to 80mV. The
other DAC codes are tested at the major transition points with V
CC
= V
DD
= 5V and CSH - CSL = 0. FB accuracy at other
DAC codes over line and load is guaranteed by design.
Note 2:
FB set voltage is 100% tested with V
CC
= V
DD
= 4.5V to 5.5V and CSH - CSL = 0mV to 80mV.
Note 3:
AC load regulation sets the AC loop gain, to make tradeoffs between output filter capacitor size and transient response,
and has only a slight effect on DC accuracy or DC load-regulation error.
Note 4:
Specifications from 0°C to -40°C are not production tested.
4
_______________________________________________________________________________________
High-Speed Step-Down Controllers with
Synchronous Rectification for CPU Power
MAX1624/MAX1625
__________________________________________Typical Operating Characteristics
(T
A
= +25°C, using the MAX1624 evaluation kit, unless otherwise noted.)
MAX1624
LOAD-TRANSIENT RESPONSE
(WITHOUT GLITCHCATCHER)
(1.1V)
MAX1624/25 TOC03
MAX1624
LOAD-TRANSIENT RESPONSE
(WITH GLITCHCATCHER)
(1.1V )
MAX1624/25 TOC02
MAX1624
LOAD-TRANSIENT RESPONSE DETAIL
(WITH GLITCHCATCHER)
(1.1V)
LG = REF
A
B
MAX1624/25 TOC01
LG = REF
A
LG = REF
A
B
B
C
C
C
D
10µs/div
A: V
OUT
, 50mV/div, AC COUPLED
B: INDUCTOR CURRENT, 10A/div
C: LOAD CURRENT, 0A TO 10A, t
RISE
= t
FALL
= 100ns
10µs/div
A: V
OUT
, 50mV/div, AC COUPLED
B: INDUCTOR CURRENT, 10A/div
C: LOAD CURRENT, 0A TO 10A, t
RISE
= t
FALL
= 100ns
10µs/div
A: PDRV, 5V/div
B: V
OUT
, 50mV/div, AC COUPLED
C: NDRV, 5V/div
D: LOAD CURRENT, 0A TO 10A, t
RISE
= t
FALL
= 100ns
MAX1624
LOAD-TRANSIENT RESPONSE
(WITHOUT GLITCHCATCHER)
(2.5V)
MAX1624/25 TOC18
MAX1624
LOAD-TRANSIENT RESPONSE
(WITH GLITCHCATCHER)
(2.5V)
MAX1624/25 TOC17
MAX1624
LOAD-TRANSIENT RESPONSE
(WITHOUT GLITCHCATCHER)
(3.5V)
LG = REF
A
MAX1624/25 TOC15
LG = REF
A
LG = REF
A
B
B
B
C
C
C
10µs/div
A: V
OUT
, 50mV/div, AC COUPLED
B: INDUCTOR CURRENT, 10A/div
C: LOAD CURRENT, 0A TO 10A, t
RISE
= t
FALL
= 100ns
10µs/div
A: V
OUT
, 50mV/div, AC COUPLED
B: INDUCTOR CURRENT, 10A/div
C: LOAD CURRENT, 0A TO 10A, t
RISE
= t
FALL
= 100ns
10µs/div
A: V
OUT
, 100mV/div, AC COUPLED
B: INDUCTOR CURRENT, 10A/div
C: LOAD CURRENT, 0A TO 11A, t
RISE
= t
FALL
= 100ns
_______________________________________________________________________________________
5
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