19-3979; Rev 0; 2/06
Overvoltage-Protection Controllers with
Status
FLAG
General Description
The MAX4838A/MAX4840A/MAX4842A are overvoltage-
protection ICs that protect low-voltage systems against
voltages of up to +28V. If the input voltage exceeds the
overvoltage trip level, the MAX4838A/MAX4840A/
MAX4842A turn off the low-cost external n-channel
FET(s) to prevent damage to the protected components.
An internal charge pump eliminates the need for external
capacitors and drives the FET gate for a simple,
robust solution.
The MAX4838A has a 7.4V overvoltage threshold, and
the MAX4840A has a 5.8V overvoltage threshold. The
MAX4842A has a 4.7V overvoltage threshold. The
MAX4838A/MAX4840A have an undervoltage-lockout
(UVLO) threshold of 3.25V, while the MAX4842A has a
UVLO of 2.5V. In addition to the single FET configura-
tion, the devices can be configured with back-to-back
external FETs to prevent currents from being back-dri-
ven into the adapter.
On power-up, the device waits for 50ms before driving
GATE high.
FLAG
is held low for an additional 50ms
after GATE goes high before deasserting. The
MAX4838A/MAX4840A/MAX4842A have an open-drain
FLAG
output. The
FLAG
output asserts immediately to
an overvoltage fault.
Additional features include a ±15kV (HBM) ESD-pro-
tected input (when bypassed with a 1µF capacitor) and
a shutdown pin (EN) to turn off the device.
All devices are offered in a small 6-pin SC70 and 6-pin
1.5mm x 1.0mm µDFN packages and are specified
over the -40°C to +85°C extended temperature range.
♦
Overvoltage Protection Up to +28V
♦
Preset 7.4V, 5.8V, or 4.7V Overvoltage Trip Level
♦
Drives Low-Cost nMOS FET
♦
Internal 50ms Startup Delay
♦
Internal Charge Pump
♦
Undervoltage Lockout
♦
±15kV ESD-Protected Input
♦
Voltage Fault
FLAG
Indicator
♦
6-Pin SC70 and µDFN Packages
♦
Lead Free
Features
MAX4838A/MAX4840A/MAX4842A
Ordering Information
PART
MAX4838AEXT+T
MAX4838AELT+
MAX4840AEXT+T
MAX4840AELT+
MAX4842AEXT+T
MAX4842AELT+*
PIN-
PACKAGE
6 SC70
6 µDFN
6 SC70
6 µDFN
6 SC70
6 µDFN
TOP
MARK
ACY
KU
ACZ
KV
ADA
KW
PKG
CODE
X6S-1
L611-1
X6S-1
L611-1
X6S-1
L611-1
Note:
All devices specified for the -40°C to +85°C extended
temperature range.
*Future
product—contact factory for availability.
+Denotes
lead-free package.
Applications
Cell Phones
Digital Still Cameras
PDAs and Palmtop Devices
MP3 Players
INPUT
+1.2V TO +28V
Typical Operating Circuit
OUTPUT
NMOS
1
IN
GATE
4
V
IO
Selector Guide
PART
OV
UVLO
TRIP
EN
THRESHOLD
LEVEL INPUT
(V)
(V)
3.25
3.25
2.50
7.4
5.8
4.7
Yes
Yes
Yes
FLAG
OUTPUT
Open-Drain
Open-Drain
Open-Drain
1µF
6
EN
2
MAX4838A
MAX4840A
MAX4842A
FLAG
3
NOTE: EN AND PULLUP
RESISTOR
GND
MAX4838A
MAX4840A
MAX4842A
Pin Configuration appears at end of data sheet.
1
________________________________________________________________
Maxim Integrated Products
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.
Overvoltage-Protection Controllers with
Status
FLAG
MAX4838A/MAX4840A/MAX4842A
ABSOLUTE MAXIMUM RATINGS
IN to GND ..............................................................-0.3V to +30V
GATE to GND ........................................................-0.3V to +12V
EN, FLAG
to GND ....................................................-0.3V to +6V
Continuous Power Dissipation (T
A
= +70°C)
6-Pin SC70 (derate 3.1mW/°C above +70°C) .............245mW
6-Pin µDFN (derate 2.1mW/°C above +70°C) ............477mW
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
= +5V (MAX4838A/MAX4840A), V
IN
= +4V (MAX4842A), T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Input Voltage Range
Undervoltage-Lockout Threshold
Undervoltage-Lockout Hysteresis
V
IN
rising
Overvoltage Trip Level
OVLO
V
IN
rising
V
IN
rising
MAX4838A
MAX4840A
MAX4842A
No load,
EN
= GND or 5V,
V
IN
= 5V (MAX4838A/MAX4840A)
No load,
EN
= GND or 4.0V,
V
IN
= 4V (MAX4842A)
V
IN
= 2.9V (MAX4838A/MAX4840A)
V
IN
= 2.2V (MAX4842A)
I
GATE
sourcing 1µA
MAX4838A/MAX4840A
MAX4842A
1.2V
≤
V
IN
< UVLO,
I
SINK
= 50µA
V
IN
≥
OVLO, I
SINK
=
1mA
1.5
0.4
EN
= GND or 5.5V
1
9
7.5
27
0.4
V
0.4
1
µA
V
V
µA
MAX4838A
MAX4840A
MAX4842A
7.0
5.5
4.4
SYMBOL
V
IN
UVLO
V
IN
falling
MAX4838A/MAX4840A
MAX4842A
CONDITIONS
MIN
1.2
3.0
2.3
3.25
2.5
50
7.4
5.8
4.7
100
80
50
80
75
200
µA
160
30
22
10
8.0
mA
µA
V
7.8
6.1
5.0
V
TYP
MAX
28.0
3.5
2.7
UNITS
V
V
mV
Overvoltage Trip Level Hysteresis
mV
IN Supply Current
I
IN
UVLO Supply Current
GATE Voltage
GATE Pulldown Current
I
UVLO
V
GATE
I
PD
V
IN
> V
OVLO
, V
GATE
= 5.5V
FLAG
Output Low Voltage
V
OL
FLAG
asserted
FLAG
Output High Leakage
EN
Input High Voltage
EN
Input Low Voltage
EN
Input Leakage
I
OH
V
IH
V
IL
I
LKG
V
FLAG
= 5.5V,
FLAG
deasserted
2
_______________________________________________________________________________________
Overvoltage-Protection Controllers with
Status
FLAG
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= +5V (MAX4838A/MAX4840A), V
IN
= +4V (MAX4842A), T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
TIMING
Startup Delay
FLAG
Blanking Time
GATE Turn-On Time
t
START
t
BLANK
t
GON
V
IN
> V
UVLO
, V
GATE
> 0.3V, Figure 1
V
GATE
> 0.3V, V
FLAG
> 2.4V, Figure 1
V
GATE
= 0.3V to 8V (MAX4838A/MAX4840A),
V
GATE
= 0.3V to 6V (MAX4842A),
C
GATE
= 1500pF, Figure 1
V
IN
increasing from 5V to 8V at 3V/µs
(MAX4838A/MAX4840A), V
IN
increasing
from 4V to 6V at 3V/µs (MAX4842A),
V
GATE
= 0.3V, C
GATE
= 1500pF, Figure 2
V
IN
increasing from 5V to 8V at 3V/µs
(MAX4838A/MAX4840A), V
IN
increasing
from 4V to 6V at 3V/µs (MAX4842A),
V
FLAG
= 0.4V, Figure 2
V
IN
increasing from 0 to 8V
(MAX4838A/MAX4840A), V
IN
increasing
from 0V to 6V (MAX4842A), I
GATE
= 80% of
I
PD
, Figure 3
V
EN
= 2.4V, V
GATE
= 0.3V, Figure 4
20
20
50
50
10
80
80
ms
ms
ms
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX4838A/MAX4840A/MAX4842A
GATE Turn-Off Time
t
GOFF
6
20
µs
FLAG
Assertion Delay
t
FLAG
5.8
µs
Initial Overvoltage Fault Delay
t
OVP
1.5
µs
Disable Time
t
DIS
2
µs
Note 1:
All parts are 100% tested at +25°C. Electrical limits across the full temperature range are guaranteed by design and
correlation.
Typical Operating Characteristics
(V
IN
= +5V (MAX4838A/MAX4840A), V
IN
= +4V (MAX4842A); Si9936DY external MOSFET in back-to-back configuration; T
A
= +25°C,
unless otherwise noted.)
SUPPLY CURRENT vs. INPUT VOLTAGE
MAX4838A toc01
REVERSE CURRENT
vs. OUTPUT VOLTAGE
MAX4838A toc02
MAX4838A/MAX4840A
GATE VOLTAGE vs. INPUT VOLTAGE
MAX4838A toc03
600
500
SUPPLY CURRENT (µA)
400
300
200
100
0
0
5
10
15
20
25
1000
SINGLE MOSFET
REVERSE CURRENT (µA)
100
12
9
GATE VOLTAGE (V)
10
6
MAX4840A
3
MAX4838A
1
BACK-TO-BACK MOSFETS
0.1
30
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
0
3
4
5
6
7
8
INPUT VOLTAGE (V)
_______________________________________________________________________________________
3
Overvoltage-Protection Controllers with
Status
FLAG
MAX4838A/MAX4840A/MAX4842A
Typical Operating Characteristics (continued)
(V
IN
= +5V (MAX4838A/MAX4840A), V
IN
= +4V (MAX4842A); Si9936DY external MOSFET in back-to-back configuration; T
A
= +25°C,
unless otherwise noted.)
MAX4842A
GATE VOLTAGE vs. INPUT VOLTAGE
MAX4838A toc04
GATE VOLTAGE vs. INPUT VOLTAGE
MAX4838A toc05
MAX4838A/MAX4840A
POWER-UP RESPONSE
MAX4838A toc06
12
11.0
I
GATE
= 0
10.5
GATE VOLTAGE (V)
I
GATE
= 4µA
9
GATE VOLTAGE (V)
MAX4842A
6
5V
0V
10V
IN
GATE
10.0
I
GATE
= 8µA
0V
5V
OUT
3
9.5
0V
5V
R
OUT
=
∞
C
OUT
= 0
20ms/div
FLAG
0
0
1
2
3
4
5
6
7
8
INPUT VOLTAGE (V)
9.0
5.0
5.1
5.2
5.3
5.4
5.5
INPUT VOLTAGE (V)
MAX4838A/MAX4840A
POWER-UP RESPONSE
MAX4838A toc07
MAX4842A
POWER-UP RESPONSE
MAX4838A toc08
MAX4842A
POWER-UP RESPONSE
MAX4838A toc09
5V
IN
0V
10V
0V
1A
I
IN
0A
5V
0V
20ms/div
R
OUT
= 5Ω
FLAG
GATE
4V
0V
8V
IN
4V
0V
8V
IN
GATE
0V
4V
0V
4V
0V
OUT
R
OUT
=
∞
C
OUT
= 0
20ms/div
FLAG
0V
800mA
0A
4V
0V
GATE
I
IN
R
OUT
= 5Ω
FLAG
20ms/div
OVERVOLTAGE RESPONSE
MAX4838A toc10
POWER-UP OVERVOLTAGE RESPONSE
MAX4838A toc11
POWER-DOWN RESPONSE
MAX4838A toc12
8V
5V
10V
0V
40mA
IN
8V
0V
GATE PULLED UP
TO IN WITH 100Ω
IN
5V
0V
10V
R
LOAD
= 50Ω
R
FLAG
= 100kΩ TO +5V
IN
GATE
5V
GATE
0V
50mA
I
GATE
GATE
0V
5V
OUT
0V
5V
FLAG
0V
10ms/div
0A
5V
0V
C
GATE
= 1500pF
400ns/div
I
GATE
FLAG
0A
5V
FLAG
0V
1µs/div
4
_______________________________________________________________________________________
Overvoltage-Protection Controllers with
Status
FLAG
Pin Description
PIN
1
2
3
4
5
6
NAME
IN
GND
FLAG
GATE
N.C.
EN
FUNCTION
Input. IN is both the power-supply input and the overvoltage sense input. Bypass IN to GND with
a 1µF capacitor or larger.
Ground
Fault Indication Output, Open-Drain, Active Low.
FLAG
is asserted low during undervoltage-
lockout and overvoltage-lockout conditions.
FLAG
is deasserted during normal operation.
Gate-Drive Output. GATE is the output of an on-chip charge pump. When V
UVLO
< V
IN
< V
OVLO
,
GATE is driven high to turn on the external n-channel MOSFET(s).
No Connection. Not internally connected for µDFN package. Connected to ground for SC70
6-pin package; connect to ground or leave unconnected.
Device Enable Input, Active Low. Drive
EN
low or connect to ground to allow normal device
operation. Drive
EN
high to turn off the external MOSFET.
MAX4838A/MAX4840A/MAX4842A
Timing Diagrams
V
IN
0V
5V (4V)
V
UVLO
t
GON
8V (6V)
t
START
V
GATE
0.3V
t
BLANK
V
FLAG
( ) MAX4842A
2.4V
V
FLAG
0.4V
( ) MAX4842A
V
GATE
0.3V
V
IN
5V (4V)
t
GOFF
8V (6V)
V
OVLO
t
FLAG
Figure 1. Startup Timing Diagram
Figure 2. Shutdown Timing Diagram
V
IN
0V
8V (6V)
V
OVLO
t
OVP
80%
V
EN
1.5V
t
DIS
V
GATE
I
GATE
0.3V
( ) MAX4842A
Figure 3. Power-Up Overvoltage Timing Diagram
Figure 4. Disable Timing Diagram
_______________________________________________________________________________________
5
MicroPython开源版块
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
