19-3655; Rev 1; 3/06
High-Voltage, Overvoltage/Undervoltage,
Protection Switch Controller
General Description
The MAX6399 is a small overvoltage and undervoltage
protection circuit. The device can monitor a DC-DC out-
put voltage and quickly disconnect the power source
from the DC-DC input load when an overvoltage condi-
tion occurs. A power-OK output signals when the
DC-DC input voltage falls below an adjustable thresh-
old. This controller architecture provides the ability to
size the external n-channel MOSFET to meet specific
load current requirements.
When the DC-DC monitored output voltage is below the
user-adjustable overvoltage threshold, the GATE output
of the MAX6399 goes high to enhance the n-channel
MOSFET. The MAX6399 offers internal charge-pump
circuitry that allows the GATE voltage to be 10V above
the input voltage (V
GS
= 10V) to fully enhance the
external n-channel MOSFET, thus minimizing the drain-
to-source resistance.
When the monitored output voltage rises above the
user-adjusted overvoltage threshold, the GATE output
rapidly pulls low to shut off the MOSFET. The MOSFET
remains latched off until either the MAX6399 input
power or
SHDN
input is cycled. The MAX6399 includes
a logic-low shutdown input that disables the GATE. An
internal overtemperature detector also disables the
gate when the MAX6399 temperature reaches the ther-
mal-shutdown threshold.
The device operates over a wide supply voltage range
(5.75V to 72V) and is offered in a small TDFN package,
fully specified from -40°C to +125°C.
Features
♦
Wide Supply Voltage Range (5.75V to 72V)
♦
Internal Charge Pump Ensures n-Channel
MOSFET is Fully Enhanced During Normal
Operation (V
GS
= 10V)
♦
Fast GATE Shutoff During Overvoltage with 20mA
Sink Capability
♦
Latches Off External n-Channel MOSFET During
High-Voltage Transients
♦
Adjustable DC-DC Input Undervoltage Threshold
Power-OK Output
♦
Adjustable DC-DC Output Overvoltage
Thresholds
♦
Overtemperature Shutdown Protection
♦
Fully Specified from -40°C to +125°C
MAX6399
Ordering Information
PART
MAX6399ATA-T
PIN-PACKAGE
8 TDFN-8
TOP
MARK
ANE
PKG
CODE
T833-2
Applications
Networking
Server
Telecom
RAID
Typical Operating Circuit
DC-DC
CONVERTER
IN
OUT
EN
12V
IN
GATE
OUT
GND
LOAD
Pin Configuration
OUT_SET
GATE
6
TOP VIEW
OUT
GND
5
8
7
MAX6399
MAX6399
*EP
1
IN
2
SHDN
3
SET
4
POK
SHDN
OUT_SET
SET
3.3V
POK
GND
TDFN
*EXPOSED PAD. CONNECT TO GND.
________________________________________________________________
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-Voltage, Overvoltage/Undervoltage,
Protection Switch Controller
MAX6399
ABSOLUTE MAXIMUM RATINGS
IN, GATE, OUT .......................................................-0.3V to +80V
SHDN.............................................................-0.3V
to (IN + 0.3V)
OUT ........................................................................-0.3V to +80V
GATE to OUT..........................................................-0.3V to +20V
OUT_SET, SET, POK ..............................................-0.3V to +12V
Maximum Current (All pins) ................................................50mA
Continuous Power Dissipation (T
A
= +70°C)
8-Pin TDFN (derate 18.2mW/°C above +70°C) .........1455mW
Operating Temperature Range .........................-40°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature Range................................................+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
= 14V; C
GATE
= 6000pF, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Supply Voltage Range
IN Supply Current
IN Undervoltage Lockout
IN Undervoltage Lockout
Hysteresis
SET Threshold Voltage
SET Threshold Hysteresis
SET Input Current
Startup Response Time
GATE Rise Time
SET to GATE Prop Delay
t
OV
V
TH (SET)
V
HYST
I
SET
t
START
SHDN
rising (Note 2)
GATE rising from GND to V
OUT
+ 8V,
C
GATE
= 6000pF, OUT = GND
SET rising from V
TH
- 100mV to
V
TH
+ 100mV
V
OUT
= V
IN
= 5V, R
GATE
to IN = 1MΩ
GATE Output-Voltage High
V
OH
V
OUT
= V
IN
; V
IN
≥
14V, R
GATE
to IN = 1MΩ
GATE Output-Voltage Low
GATE Charge-Pump Current
GATE to OUT Clamp Voltage
SHDN
Logic-High Input Voltage
SHDN
Logic-Low Input Voltage
SHDN
Input Pulldown Current
Thermal-Shutdown Temperature
(Note 3)
Thermal-Shutdown Hysteresis
POWER-OK (POK)
OUT_SET Threshold
V
TH
(OUT_SET)
SYMBOL
V
IN
I
IN
SHDN
= high
SHDN
= low
CONDITIONS
MIN
5.75
TYP
100
10
MAX
72.00
130
22
5.50
UNITS
V
µA
V
mV
V
IN
rising, enables GATE
V
IN
falling, GATE off
With respect to GND, SET rising
4.68
5
155
0.480
-50
0.5
5
0.517
+50
V
% V
TH
nA
µs
ms
100
1
0.5
V
IN
+
3.6V
V
IN
+
15V
V
IN
+
3.8V
V
IN
+
10V
75
13.8
1.4
0.4
18.0
V
IN
+
4.0V
µs
V
V
IN
+
10.7V
0.3
V
µA
V
V
V
µA
°C
°C
V
OL
I
GATE
V
CLMP
V
IH
V
IL
GATE sinking 20mA, V
OUT_SET
= GND
GATE = GND
V
SHDN
= 2V,
SHDN
is internally pulled
down to GND
1
+150
20
OUT_SET rising
1.205
1.23
1.258
V
2
_______________________________________________________________________________________
High-Voltage, Overvoltage/Undervoltage,
Protection Switch Controller
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 14V; C
GATE
= 6000pF, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
OUT_SET Hysteresis
OUT_SET to POK Delay
POK Output Voltage Low
POK Leakage Current
V
OL
V
OUT_SET
rising or falling
V
IN
≥
1.5V, I
SINK
= 3.2mA, POK asserted
V
OUT_SET
= 1.4V
SYMBOL
CONDITIONS
MIN
TYP
5
35
0.45
100
MAX
UNITS
% V
TH
(OUT_SET)
MAX6399
µs
V
nA
Note 1:
Specifications to -40°C are guaranteed by design and not production tested.
Note 2:
The MAX6399 powers up with the external FET in off mode (V
GATE
= GND). The external FET turns on t
START
after the
device is powered up and all input conditions are valid.
Note 3:
For accurate overtemperature shutdown performance, place the device in close thermal contact with the external MOSFET.
Typical Operating Characteristics
(V
IN
= 14V, C
GATE
= 6nF, unless otherwise noted.)
SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX6399 toc01
MAX6399 toc02
SUPPLY CURRENT vs. INPUT VOLTAGE
150
140
130
SUPPLY CURRENT (µA)
120
110
100
90
80
70
60
50
40
0
20
40
INPUT VOLTAGE (V)
60
80
GATE ON
20
18
16
SUPPLY CURRENT (µA)
14
12
10
8
6
4
2
0
0
GATE-DRIVE VOLTAGE
vs. INPUT VOLTAGE
V
OUT
= V
IN
10
V
GATE
- V
OUT
(V)
8
6
4
2
0
MAX6399 toc03
12
GATE OFF
20
40
INPUT VOLTAGE (V)
60
80
4
6
8
10 12 14 16 18 20 22 24
INPUT VOLTAGE (V)
UVLO THRESHOLD vs. TEMPERATURE
MAX6399 toc04
SET THRESHOLD
vs. TEMPERATURE
508
SET THRESHOLD VOLTAGE (V)
506
504
502
500
498
496
494
492
490
MAX6399 toc05
OUT_SET THRESHOLD
vs. TEMPERATURE
1.25
1.24
1.23
1.22
1.21
1.20
1.19
1.18
1.17
1.16
OUT_SET FALLING
OUT_SET RISING
MAX6399 toc06
6.0
5.8
5.6
5.4
V
UVLO
(V)
5.2
5.0
4.8
4.6
4.4
4.2
4.0
-50
-25
0
25
50
75
100
510
1.26
OUT_SET THRESHOLD VOLTAGE (V)
125
-50
-25
0
25
50
75
100
125
-50
-25
0
25
50
75
100
125
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
3
High-Voltage, Overvoltage/Undervoltage,
Protection Switch Controller
MAX6399
Typical Operating Characteristics (continued)
(V
IN
= 14V, C
GATE
= 6nF, unless otherwise noted.)
GATE-TO-OUT CLAMP VOLTAGE
vs. TEMPERATURE
MAX6399 toc07
GATE-DRIVE VOLTAGE
vs. TEMPERATURE
MAX6399 toc08
STARTUP WAVEFORM
MAX6399 toc09
17.0
GATE-TO-OUT CLAMP VOLTAGE (V)
16.9
16.8
16.7
16.6
16.5
16.4
16.3
16.2
16.1
16.0
-50
-25
0
25
50
75
100
10.500
10.495
GATE-DRIVE VOLTAGE (V)
10.490
10.485
10.480
10.475
10.470
10.465
10.460
10.455
10.450
POK PULLED
TO 3.3V
V
UV
= 9V
V
IN
10V/div
V
GATE
10V/div
V
OUT
10V/div
V
POK
5V/div
-50
-25
0
25
50
75
100
125
2ms/div
TEMPERATURE (°C)
125
TEMPERATURE (°C)
STARTUP WAVEFORM (SHDN RISING)
MAX6399 toc10
OVERVOLTAGE SWITCH FAULT
MAX6399 toc11
POK PULLED TO 3.3V
V
SHDN
2V/div
V
GATE
10V/div
V
OV
= 4V
V
IN
= 14V
3.3V
4V
V
DC_DC
100mV/div
V
GATE
10V/div
V
OUT
10V/div
V
POK
5V/div
400µs/div
V
OUT
10V/div
UNDERVOLTAGE FAULT
MAX6399 toc12
V
IN
5V/div
V
GATE
20V/div
V
OUT
10V/div
V
UV
= 9V
POK PULLED
TO 3.3V
100µs/div
V
POK
5V/div
4
_______________________________________________________________________________________
High-Voltage, Overvoltage/Undervoltage,
Protection Switch Controller
MAX6399
Pin Description
PIN
1
2
NAME
IN
SHDN
FUNCTION
Supply Voltage Input. Bypass with a 10µF capacitor (minimum).
Shutdown Input. Drive
SHDN
low to force GATE low, turning off the external n-channel MOSFET.
SHDN
is
internally pulled down to GND with a 1µA current source. Toggle
SHDN
to unlatch GATE after an
overvoltage condition. Connect to IN for normal operation.
Overvoltage Threshold Adjustment Input. Use SET to monitor a system output voltage. Connect SET to an
external resistor voltage-divider network to adjust the desired overvoltage limit threshold. GATE is quickly
turned off when SET rises above its 0.5V (typ) threshold.
Power-OK Open-Drain Output. POK asserts low when OUT_SET falls below its 1.23V (typ) threshold.
Ground
Gate-Drive Output. Connect GATE to the gate of an external n-channel FET. GATE is a charge pump with a
100µA pullup current to IN + 10V (typ) during normal operation. GATE is quickly turned off during an
overvoltage condition. GATE remains latched off until the power is recycled or
SHDN
is toggled. GATE pulls
low when
SHDN
is low.
Output Voltage-Sense Input. Connect to the source of the external n-channel MOSFET.
3
4
5
SET
POK
GND
6
GATE
7
8
—
OUT
Undervoltage Detector Input. Use OUT_SET to monitor the source of the MOSFET. Connect a
OUT_SET resistor-divider from OUT to OUT_SET to adjust the desired undervoltage threshold. POK asserts low
when OUT_SET falls below its 1.23V threshold.
EP
Exposed Pad. Connect to ground plane.
Detailed Description
IN
THERMAL
PROTECTION
UVLO
CHARGE
PUMP
5V
SET
GATE
0.5V
OUT
MAX6399
1.23V
SHDN
POK
GND
OUT_SET
Figure 1. Functional Diagram
The MAX6399 is an ultra-small, low-current protection
circuit utilized in DC-DC converter applications. The
MAX6399 monitors the input and output voltages of a
DC-DC converter for undervoltage and overvoltage
conditions. The MAX6399 controls an external n-chan-
nel MOSFET to isolate the load during an overvoltage
condition. The device allows system designers to size
the external n-channel MOSFET to their load current
and board size.
The MAX6399 drives the MOSFET’s gate high when the
monitored DC-DC output voltage is below the program-
mable overvoltage threshold, programmed through
SET. An internal charge-pump circuit provides a guar-
anteed 10V gate-to-source drive to ensure low input-to-
load voltage drops in normal operating modes. When
the monitored DC-DC output voltage rises above the
user-adjusted overvoltage threshold, GATE latches low,
turning off the MOSFET. The MOSFET remains off until
the power is recycled or by toggling
SHDN.
The MAX6399 also monitors for an undervoltage condi-
tion at the input of the DC-DC converter through
OUT_SET. An active-high, open-drain, power-good out-
put can be used to drive the EN input, notifying the sys-
tem when the monitored voltage is below the adjusted
undervoltage voltage threshold.
_______________________________________________________________________________________
5
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