19-3420; Rev 0; 9/04
BLE
IT AVAILA
UATION K
EVAL
High-Current, Low-Voltage Linear Regulator
with Power-Limited, External MOSFET
General Description
Features
♦
Low-Cost, High-Current Linear Regulator
♦
External MOSFET Protection
MOSFET Power Limit
50mV (typ) Current Limit
Thermal Limit
♦
1.0V to 5.5V Input Supply Voltage
♦
1.2V or 1.5V Preset, or Adjustable Output Voltage
♦
Power-Good (PGOOD) Open-Drain Output with
3ms Startup Delay
♦
Programmable Soft-Start
♦
Shutdown with Output Discharge
MAX8704
The MAX8704 high-current linear regulator uses an
external n-channel MOSFET to generate low-voltage
supplies for notebook computers. This linear regulator
delivers an output voltage as low as 0.5V from an input
voltage as low as 1.0V. Normally, this low input require-
ment would make the design of such a regulator very dif-
ficult. In this application, the 5V bias supply that is
always available in the system powers the MAX8704 dri-
ver and control circuitry.
The MAX8704 includes a fixed current limit and an
adjustable power limit to protect the external MOSFET
from overheating. Additionally, the MAX8704 includes
an internal thermal limit to prevent damage to the con-
troller and provide remote thermal protection for the
external MOSFET.
The MAX8704 features an adjustable soft-start function
and generates a delayed power-good (PGOOD) signal
that signals when the linear regulator is in regulation.
The MAX8704 is available in a 10-pin µMAX
®
package.
Applications
V
MCH
and V
CCP
CPU Supplies
Notebook Computers
Desktop Computers
Servers
VID Power Supplies
Low-Voltage Bias Supplies
PART
MAX8704EUB
Ordering Information
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
10 µMAX
Pin Configuration
TOP VIEW
V
IN
1
V
CC
PGOOD
PLIM
SS/EN
2
3
4
5
10 DRV
9
GND
CSP
CSN
FB
MAX8704
8
7
6
µMAX
µMAX is a registered trademark of Maxim Integrated Products, Inc.
________________________________________________________________
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.
High-Current, Low-Voltage Linear Regulator
with Power-Limited, External MOSFET
MAX8704
ABSOLUTE MAXIMUM RATINGS
V
CC
, V
IN
to GND.......................................................-0.3V to +6V
CSP, CSN, DRV to GND ...........................................-0.3V to +6V
FB, PLIM, SS/EN, PGOOD to GND.............-0.3V to (V
CC
+ 0.3V)
Continuous Power Dissipation (T
A
= +70°C)
10-Pin µMAX (derated 5.6mW/°C above +70°C) .........444mW
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
IN
= 2.5V, V
CC
= 5.0V, PLIM = FB = GND, CSP = CSN, SS/EN floating,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values
are at T
A
= +25°C.)
PARAMETER
Input Voltage Range
Preset Output Voltage
(Fixed)
Feedback Voltage Accuracy
(Adjustable)
Load-Regulation Error
Line-Regulation Error
FB Input Bias Current
CSN Input Bias Current
DRV Output Voltage Swing
DRV Slew Rate
Quiescent Supply Current (V
CC
)
Quiescent Supply Current (V
IN
)
Shutdown Supply Current (V
CC
)
Shutdown Supply Current (V
IN
)
FAULT DETECTION
Thermal-Shutdown Threshold
V
CC
Undervoltage-Lockout
Threshold
Current-Limit Threshold
Power-Limit Threshold
Power-Limit Conversion Gain
Power-Limit Conversion Gain
Variation
V
CSLIMIT
V
PWRLIMIT
K
PLIM
T
SHDN
Rising edge, 20°C hysteresis
Rising edge, 15mV hysteresis
PLIM = GND
Rising edge
V
CSP
- V
CSN
= 30mV, V
CSN
= 0.5V,
V
IN
= 3.5V
V
CSP
- V
CSN
= 25mV to 45mV, V
CSN
= 0.5V,
V
IN
= 2V to 4.5V
45
0.96
155
+140
4.2
50
1.0
200
±12
4.45
57
1.04
233
°C
V
mV
V
µA/V
2
%
I
CC
I
IN
I
FB
I
CSN
V
DRV
SYMBOL
V
IN
V
CC
V
OUT
V
FB
FB = V
CC
FB = GND
FB = CSN
V
CSP
- V
CSN
= 45mV
V
IN
= 1V to 5.5V
V
FB
= 0.6V
V
CSN
= 1.6V
Output high
Output low
C
DRV
= 40nF
FB forced above the regulation point,
V
CSN
= 1.6V
FB forced above the regulation point,
V
CSN
= 1.6V
SS/EN = GND
SS/EN = GND
V
CC
-
1.0
-1
50
V
CC
-
0.7
0.7
0.2
1.5
5
35
5
3
10
70
10
1.0
V/µs
mA
µA
µA
µA
CONDITIONS
MIN
1.0
4.5
1.462
1.170
490
-2.5
1.50
1.20
500
-2
0.01
+1
100
TYP
MAX
5.5
5.5
1.538
1.230
510
UNITS
V
V
mV
%
%
µA
µA
V
2
_______________________________________________________________________________________
High-Current, Low-Voltage Linear Regulator
with Power-Limited, External MOSFET
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 2.5V, V
CC
= 5.0V, PLIM = FB = GND, CSP = CSN, SS/EN floating,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values
are at T
A
= +25°C.)
PARAMETER
PLIM Output Current
PLIM Output Current Offset
CSP Input Current
SOFT-START AND SHUTDOWN
Soft-Start Charge Current
SS/EN Full Current Threshold
SS/EN Enable Threshold
SS/EN Discharge Current
Discharge-Mode On-Resistance
INPUTS AND OUTPUTS
PGOOD Trip Threshold
PGOOD Startup Delay
PGOOD Output Low Voltage
PGOOD Leakage Current
I
PGOOD
I
SINK
= 4mA
V
FB
= 1.0V (PGOOD high impedance),
PGOOD forced to 5V
-1
With respect to error-comparator threshold,
2% hysteresis
-10
1
-8
3
-6
5
0.3
+1
%
ms
V
µA
I
SS/EN
R
CSN
Rising edge
V
SS/EN
= 1.5V, thermal fault, bias fault
condition, or UVLO
0.4
I
SS
V
SS/EN
= 1.5V
4
5
2
0.5
10
10
0.6
20
6
µA
V
V
µA
Ω
SYMBOL
CONDITIONS
V
CSP
- V
CSN
= 30mV, V
IN
= 3.5V,
V
CSN
= 0.5V
CSP = CSN, V
IN
= 1.0V, V
CSN
= 0.5V
V
CSN
= 1.50V, V
CSP
= 1.55V
-1
MIN
14
TYP
18
0.5
MAX
21
2
+1
UNITS
µA
µA
µA
MAX8704
ELECTRICAL CHARACTERISTICS
(V
IN
= 2.5V, V
CC
= 5.0V, PLIM = FB = GND, CSP = CSN, SS/EN floating,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER
Input Voltage Range
Preset Output Voltage
(Fixed)
Feedback Voltage Accuracy
(Adjustable)
DRV Output Voltage Swing
SYMBOL
V
IN
V
CC
V
OUT
V
FB
FB = V
CC
FB = GND
FB = CSN
Output high
Output low
Quiescent Supply Current (V
CC
)
Quiescent Supply Current (V
IN
)
Shutdown Supply Current (V
CC
)
Shutdown Supply Current (V
IN
)
I
CC
I
IN
FB forced above the regulation point,
V
CSN
= 1.6V
FB forced above the regulation point,
V
CSN
= 1.6V
SS/EN = GND
SS/EN = GND
CONDITIONS
MIN
1.0
4.5
1.455
1.158
485
V
CC
-
1.1
1.1
3
10
70
10
mA
µA
µA
µA
MAX
5.5
5.5
1.545
1.242
515
UNITS
V
V
mV
V
DRV
V
_______________________________________________________________________________________
3
High-Current, Low-Voltage Linear Regulator
with Power-Limited, External MOSFET
MAX8704
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 2.5V, V
CC
= 5.0V, PLIM = FB = GND, CSP = CSN, SS/EN floating,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 1)
PARAMETER
FAULT DETECTION
V
CC
Undervoltage-Lockout
Threshold
Current-Limit Threshold
Power-Limit Threshold
PLIM Output Current
SOFT-START AND SHUTDOWN
Soft-Start Charge Current
SS/EN Enable Threshold
INPUTS AND OUTPUTS
PGOOD Trip Threshold
PGOOD Startup Delay
PGOOD Output Low Voltage
I
SINK
= 4mA
With respect to error-comparator threshold,
2% hysteresis
-11
0.5
-5
5.5
0.3
%
ms
V
I
SS
V
SS/EN
= 0
Rising edge
4
0.4
6
0.6
µA
V
V
CSLIMIT
V
PWRLIMIT
Rising edge, 15mV hysteresis
PLIM = GND
Rising edge
V
CSP
- V
CSN
= 30mV, V
IN
= 3.5V,
V
CSN
= 0.5V
43
0.90
13
4.45
60
1.10
22
V
mV
V
µA
SYMBOL
CONDITIONS
MIN
MAX
UNITS
Note 1:
Specifications to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics
(Circuit of Figure 1, V
OUT
= 1.5V, T
A
= +25°C, unless otherwise noted.)
OUTPUT VOLTAGE DEVIATION
vs. LOAD CURRENT
MAX8704 toc01
PLIM VOLTAGE vs. LOAD CURRENT
MAX8704 toc02
OUTPUT VOLTAGE
vs. INPUT VOLTAGE
1.6
1.4
1.2
V
OUT
(V)
10mA LOAD
MAX8704 toc03
0
-0.5
V
OUT
DEVIATION (%)
-1.0
-1.5
-2.0
-2.5
-3.0
0
1
2
3
4
5
LOAD CURRENT (A)
V
IN
= 3.3V
V
IN
= 1.8V
1.5
POWER LIMIT
1.2
PLIM VOLTAGE (V)
V
IN
= 3.3V
1.8
0.9
V
IN
= 2.5V
V
IN
= 1.8V
1.0
0.8
0.6
0.4
1A LOAD
0.6
0.3
CURRENT LIMIT
0
0
1
2
3
4
5
LOAD CURRENT (A)
0.2
0
1
2
3
INPUT VOLTAGE (V)
4
5
4
_______________________________________________________________________________________
High-Current, Low-Voltage Linear Regulator
with Power-Limited, External MOSFET
Typical Operating Characteristics (continued)
(Circuit of Figure 1, V
OUT
= 1.5V, T
A
= +25°C, unless otherwise noted.)
PLIM VOLTAGE
vs. INPUT VOLTAGE
MAX8704 toc04
MAX8704
5V BIAS SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX8704 toc05
MOSFET POWER DISSIPATION
vs. DRAIN-TO-SOURCE VOLTAGE
MAX8704 toc06
1.5
5
1A LOAD
BIAS SUPPLY CURRENT (mA)
4
2.5
1.2
PLIM VOLTAGE (V)
OUTPUT SHORT
2.0
1A LOAD
POWER (W)
0.9
1A LOAD
0.6
3
1.5
OUTPUT SHORT
1.0
2
POWER LIMIT
1
DROPOUT
0
0.3
10mA LOAD
0.5
0
1
2
3
INPUT VOLTAGE (V)
4
5
0
1
2
3
INPUT VOLTAGE (V)
4
5
1
2
3
V
DS
(V)
4
5
OUTPUT CURRENT LIMIT
vs. SS/EN VOLTAGE
MAX8704 toc07
SOFT-START
(C
SS
= 10nF)
2V
1V
SHUTDOWN SEQUENCE
(NO LOAD)
MAX8704 toc08
MAX8704 toc09
6
5
CURRENT LIMIT (A)
4
3
2
1
0
0
0.5
1.0
1.5
2.0
2.5
5V
0
A
5V
0
B
1.5V
A
0
1.5V
0
1A
0
3.0
C
B
C
0
1A
0
200µs/div
A. EN/SS, 1V/div
C. FET CURRENT, 1A/div
B. LDO OUTPUT, 1V/div
1.5Ω LOAD, V
IN
= 1.8V
D
1ms/div
C. LDO OUTPUT, 1V/div
A. PGOOD, 5V/div
D. FET CURRENT, 2A/div
B. EN/SS, 5V/div
NO LOAD, C
SS
= 1nF, V
IN
= 1.8V
SS/EN VOLTAGE (V)
_______________________________________________________________________________________
5
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
