19-3705; Rev 0; 5/05
KIT
ATION
EVALU
BLE
AVAILA
Dual, Low-Voltage Linear Regulator Controllers
with External MOSFETs
General Description
The MAX8737 dual high-power linear regulator con-
trollers use external n-channel MOSFETs to generate
two independent low-voltage supplies for notebook
computers. The MAX8737 delivers low output voltages
from 0.5V to 2.5V (±5mV no-load accuracy). The exter-
nal components allow scalable current design with
loads up to 5A with excellent load regulation (1%). The
regulator operates from a low input voltage, which also
reduces the power dissipation in the external n-channel
MOSFET. The controller powers the external MOSFET
gate driver from the standard 5V system supply.
The MAX8737 includes current and thermal limits to
prevent damage to the linear regulator. The MAX8737
uses an external resistive divider to fold back the cur-
rent limit, reducing the overall power dissipation. The
MAX8737 uses an external resistive-divider in series
with the current-sense input (CS_), providing foldback
current-limit protection, and effectively reducing the
short-circuit power dissipation.
An output undervoltage timeout is available for low-cost
applications that omit the current-sense resistor. The
output undervoltage (UVP) timing depends on the mag-
nitude of the voltage at V
OUT
. The UVP detects and
shuts down the LDO if the output voltage drops out of
regulation. The controller uses an adjustable reference
input (REFIN_) to set the nominal output voltage
(V
OUT_
), which minimizes the cost and makes the sta-
bility independent of the output voltage.
Each linear regulator features an adjustable soft-start
function, and generates a delayed power-good
(PGOOD) signal that signals when the linear regulator
is in regulation. The MAX8737 is a low-cost solution
requiring few external components and is available in a
small, 4mm x 4mm, 16-pin thin QFN package.
♦
Low-Cost Dual Linear Regulators
♦
Output Voltage Accuracy ±5mV
♦
Independent 0.5V to 2.5V Reference Inputs
♦
Foldback Current-Limit Protection
♦
Output Undervoltage-Lockout Protection
♦
Thermal Limit (Internal Sensor)
♦
1.0V to 5.5V Input Supply Voltage (External FET
Drain)
♦
5V Bias Supply Voltage
♦
Independent Power-Good Open-Drain Outputs
♦
Independent Enable Inputs
♦
Soft-Shutdown Output Discharge
♦
Low Supply Current (0.5mA)
♦
5µA (max) Shutdown Supply Current
Features
MAX8737
Ordering Information
PART
MAX8737ETE
TEMP RANGE PIN-PACKAGE
-40°C to +85°C 16 Thin QFN-EP* 4mm x 4mm
MAX8737ETE+ -40°C to +85°C 16 Thin QFN-EP* 4mm x 4mm
*EP
= Exposed pad.
+Denotes
lead-free packaging.
Pin Configuration
TOP VIEW
REFIN2
9
OUT2
10
N.C.
12
Applications
Notebook and Desktop Computers
Point-of-Load Regulators
V
MCH
and V
CCP
CPU Supplies
Low-Voltage Bias Supplies
Servers
DRV1 16
N.C. 14
DRV2 13
11
CS2
8
7
EN1
EN2
PGOOD1
PGOOD2
MAX8737
GND 15
6
5
1
V
CC
2
CS1
3
OUT1
4
REFIN1
4mm x 4mm TQFN
________________________________________________________________
Maxim Integrated Products
1
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.
Dual, Low-Voltage Linear Regulator Controllers
with External MOSFETs
MAX8737
ABSOLUTE MAXIMUM RATINGS
V
CC
to GND ..............................................................-0.3V to +6V
OUT1, OUT2 to GND................................................-0.3V to +6V
REFIN1, REFIN2, PGOOD1, PGOOD2, EN1,
EN2 to GND..........................................................-0.3V to +6V
DRV1, DRV2, CS1, CS2 to GND.................-0.3V to (V
CC
+ 0.3V)
Continuous Power Dissipation (T
A
= +70°C)
16-Pin 4mm x 4mm Thin QFN (derated 25mW/°C
above +70°C).............................................................2000mW
Operating Temperature Range
MAX8737ETE ...................................................-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, EN_ = CS_ = V
CC
, V
REFIN
= 1.0V,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Supply Voltage Range
V
CC
Undervoltage Lockout
Threshold
V
CC
Quiescent Supply Current
V
CC
Shutdown Supply Current
REFIN to OUT Offset Voltage
OUT_ Input Bias Current
DRIVERS
DRV_ Output Voltage Swing
(Note 1)
DRV_ Maximum Sourcing Current
DRV_ Maximum Sinking Current
OUT_ to DRV_ Transconductance
(Large Signal)
DRV_ Power-Supply Rejection
Ratio
DRV_ Soft-Start Charging Current
REFERENCE INPUT
REFIN_ Voltage Range
REFIN_ Input Bias Current
FAULT PROTECTION
Thermal Shutdown Threshold
Current-Limit Threshold
CS_ Input Current
Linear Regulator UVP Threshold
(Slow)
UVP
(SLOW)
With respect to V
REFIN
; CS_ = V
CC
T
SHDN
V
ILIM
Hysteresis = 20°C
V
CS
_ - V
OUT
_
T
A
= 0°C to +85°C
T
A
= +85°C
7
7.5
-1
72
80
+125
10
10
13
12.5
+1
88
°C
mV
µA
%
V
REFIN
_
I
REFIN
_
V
CC
= 4.75V to 5.5V
V
REFIN
_ = 0 to 2.5V
0.5
-100
-10
2.5
+100
V
nA
I
SOFT
G
MDRV
10Hz < f < 10kHz, I
DRV
= 1mA, C
DRV
=
10nF
40
Output high; V
OUT
_ = V
REFIN
_ - 25mV,
I
LOAD
= 1mA
Output low; V
OUT
_ = V
REFIN
_ + 25mV,
I
LOAD
= 1mA
V
OUT
_ = V
REFIN
_ - 25mV; V
DRV
= 3V
V
OUT
_ = V
REFIN
_ + 25mV; V
DRV
= 3V
6
6
V
CC
-
0.3
V
CC
-
0.05
V
0.03
14
14
0.8
-80
170
400
0.3
mA
mA
S
dB
µA
V
OUT
_
I
OUT
_
I
CC
SYMBOL
V
CC
Rising edge, 200mV hysteresis (typ)
EN1 = EN2 = V
CC
EN1 = EN2 = GND
-5
-1
CONDITIONS
MIN
4.75
4.1
4.35
0.5
0.1
TYP
MAX
5.50
4.6
1
5
+5
+1
UNITS
V
V
mA
µA
mV
µA
2
_______________________________________________________________________________________
Dual, Low-Voltage Linear Regulator Controllers
with External MOSFETs
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 5V, EN_ = CS_ = V
CC
, V
REFIN
= 1.0V,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
MAX8737
PARAMETER
Linear Regulator UVP Threshold
(Fast)
Slow Short-Circuit Timer Duration
Fast Short-Circuit Timer Duration
Discharge-Mode On-Resistance
OUT_ Pin
INPUTS AND OUTPUTS
EN_ Input Low Level
EN_ Input High Level
Enable Leakage Current
Power-Good Trip Threshold
(Lower)
Power-Good Startup Delay
Power-Good Propagation Delay
Power-Good Output Low Voltage
Power Good Leakage Current
SYMBOL
UVP
(FAST)
CONDITIONS
With respect to V
REFIN
; CS_ = V
CC
MIN
54
TYP
60
75
5
10
MAX
66
UNITS
%
µs
µs
Ω
t
UVP(SLOW)
With respect to V
REFIN
; CS_ = V
CC
t
UVP(FAST)
R
OUT
With respect to V
REFIN
; CS_ = V
CC
0.6
Rising edge, 200mV (typ) hysteresis
With respect to error comparator threshold,
hysteresis = 4% (falling edge)
1.6
-1
-15
-12
2
t
PGOOD
OUT_ forced 2% beyond PGOOD_ trip
threshold
I
SINK
= 4mA
I
GOO
V
OUT
_ = 1.0V (PGOOD_ high impedance),
1
1
0.3
+1
-9
V
V
µA
%
ms
µs
V
µA
ELECTRICAL CHARACTERISTICS
(V
CC
= 5V, EN_ = CS_ = V
CC
, V
REFIN
= 1.0V,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 2)
PARAMETER
Supply Voltage Range
V
CC
Undervoltage Lockout
Threshold
V
CC
Quiescent Supply Current
V
CC
Shutdown Supply Current
REFIN to OUT Offset Voltage
DRIVERS
DRV_ Output Voltage Swing
(Note 1)
DRV_ Maximum Sourcing Current
DRV_ Maximum Sinking Current
DRV_ Soft-Start Charging Current
I
SOFT
Output high; V
OUT
_ = V
REFIN
_ - 25mV;
I
LOAD
= 1mA
Output low; V
OUT
_ = V
REFIN
_ + 25mV:
I
LOAD
= 1mA
V
OUT
_ = V
REFIN
_ - 25mV; V
DRV
= 3V
V
OUT
_ = V
REFIN
_ + 25mV; V
DRV
= 3V
3.5
3.5
40
400
V
CC
-
0.3
V
0.3
mA
mA
µA
V
OUT
_
I
CC
SYMBOL
V
CC
Rising edge 200mV hysteresis (typ)
EN1 = EN2 = V
CC
EN1 = EN2 = GND
-7
CONDITIONS
MIN
4.75
4.1
TYP
MAX
5.50
4.6
1.5
5
+7
UNITS
V
V
mA
µA
mV
_______________________________________________________________________________________
3
Dual, Low-Voltage Linear Regulator Controllers
with External MOSFETs
MAX8737
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 5V, EN_ = CS_ = V
CC
, V
REFIN
= 1.0V,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 2)
PARAMETER
REFERENCE INPUT
REFIN_ Voltage Range
FAULT PROTECTION
Current-Limit Threshold
Linear Regulator UVP Threshold
(Slow)
Linear Regulator UVP Threshold
(Fast)
INPUTS AND OUTPUTS
EN_ Input Low Level
EN_ Input High Level
Power-Good Trip Threshold
(Lower)
Power-Good Output Low Voltage
With respect to error comparator threshold,
hysteresis = 4% (falling edge)
I
SINK
= 4mA
1.6
-15
-9
0.3
0.6
V
V
%
V
V
ILIM
V
CS
_ - V
OUT
_
6.5
72
54
13.5
88
66
mV
%
%
V
REFIN
_
V
CC
= 4.75V to 5.5V
0.5
2.5
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
UVP
(SLOW)
With respect to V
REFIN
; CS_ = V
CC
UVP
(FAST)
With respect to V
REFIN
; CS_ = V
CC
Note 1:
Low threshold n-channel MOSFET is required for 2.5V (±2%) output.
Note 2:
Specifications to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics
(Circuit of Figure 1, T
A
= +25°C, unless otherwise noted.)
OUTPUT-VOLTAGE DEVIATION
vs. LOAD CURRENT
MAX8737 toc01
FOLDBACK CURRENT LIMIT
vs. OUTPUT VOLTAGE
2.8
2.4
CURRENT LIMIT (A)
2.0
1.6
1.2
0.8
MAX8737 toc02
SOFT-START
(EN RISING EDGE)
MAX8737 toc03
5
OUTPUT-VOLTAGE DEVIATION (mV)
4
3
2
1
0
-1
-2
-3
-4
-5
0
0.5
1.0
LOAD CURRENT (A)
1.5
V
OUT
= 1.5V
3.2
5V
0
3V
A
B
0
1.5V
C
0
5V
0
0
0.5
1.0
1.5
A. EN1, 5V/div
B. DRV1, 2V/div
NO LOAD
1ms/div
C. LDO1 OUTPUT, 1V/div
D. PGOOD1, 5V/div
D
0.4
0
2.0
OUTPUT VOLTAGE (V)
4
_______________________________________________________________________________________
Dual, Low-Voltage Linear Regulator Controllers
with External MOSFETs
MAX8737
Typical Operating Characteristics (continued)
(Circuit of Figure 1, T
A
= +25°C, unless otherwise noted.)
SOFT-STOP
(EN FALLING EDGE)
MAX8737 toc04
SOFT-START
(UVLO RISING EDGE)
MAX8737 toc05
SOFT-STOP
(UVLO FALLING EDGE)
MAX8737 toc06
5V
0
3V
A
5V
0
3V
A
5V
0
3V
A
B
0
1.5V
C
0
5V
0
100µs/div
A. EN1, 5V/div
B. DRV1, 2V/div
NO LOAD
C. LDO1 OUTPUT, 1V/div
D. PGOOD1, 5V/div
D
0
5V
0
2ms/div
A. 5V BIAS (V
CC
), 5V/div
B. DRV1, 2V/div
NO LOAD, EN = V
CC
0
1.5V
B
0
1.5V
C
0
5V
D
0
2ms/div
A. 5V BIAS (V
CC
), 5V/div
B. DRV1, 2V/div
NO LOAD, EN = V
CC
B
C
D
C. LDO1 OUTPUT, 1V/div
D. PGOOD1, 5V/div
C. LDO1 OUTPUT, 1V/div
D. PGOOD1, 5V/div
LOAD TRANSIENT
(0.1A TO 2.1A)
MAX8737 toc07
LOAD TRANSIENT
(NO LOAD TO 2A)
MAX8737 toc08
LOAD TRANSIENT
(NO LOAD TO 2A)
MAX8737 toc09
0
2.1A
A
0
2A
0
3.2V
2.7V
1.7V
A
0
2A
A
B
0.1A
3.2V
2.8V
1.51V
1.50V
1.49V
10µs/div
A. CONTROL SIGNAL
C. DRV1, 500mV/div
B. LOAD CURRENT, 2A/div D. LDO1 OUTPUT VOLTAGE,
10mV/div
D
C
B
B
0
C
3.2V
2.7V
C
1.50V
1.45V
10µs/div
D
1.50V
1.45V
2µs/div
D
A. CONTROL SIGNAL
C. DRV1, 1V/div
B. LOAD CURRENT, 2A/div D. LDO1 OUTPUT VOLTAGE,
50mV/div
A. CONTROL SIGNAL
C. DRV1, 1V/div
B. LOAD CURRENT, 2A/div D. LDO1 OUTPUT VOLTAGE,
50mV/div
_______________________________________________________________________________________
5
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