General Description
The MAX4919B/MAX4920B/MAX4921B overvoltage
protection controllers protect low-voltage systems
against high-voltage faults up to +28V. An internal 1.8A
(min) pFET with low RON (100mΩ) switches a battery to
the load and also protects the battery against short-cir-
cuit faults. When a short circuit occurs, the current
through the internal pFET is limited for a blanking peri-
od. If the short condition is present after the blanking
period, the switch is latched off and remains off until
one of the input signals (IN, HP_PWR, PWR_ON) is
cycled. The pFET is turned on by a logic-high voltage
at PWR_HOLD, HP_PWR, PWR_ON, or IN .
The overvoltage thresholds (OVLO) are preset to
+6.38V (MAX4919B), +5.80V (MAX4920B), and +4.65V
(MAX4921B). When the input voltage drops below the
undervoltage lockout (UVLO) threshold, the devices enter
a low-current standby mode. In shutdown mode, the
current is reduced to 0.4µA. The MAX4919B/MAX4920B
have a +4.27V UVLO threshold, and the MAX4921B has
a +2.35V UVLO threshold.
The MAX4919B/MAX4920B/MAX4921B are offered in a
small 14-pin TDFN package (3mm x 3mm) with an
exposed paddle and are specified over the extended
-40°C to +85°C temperature range.
Applications
Cell Phones
Digital Still Cameras
PDAs and Palmtop Devices
MP3 Players
Features
♦Input Overvoltage Protection Up to +28V
♦Preset Overvoltage Protection Trip Level
6.38V (MAX4919B)
5.80V (MAX4920B)
4.65V (MAX4921B)
♦Adapter/Car-Kit Auto-Selector
♦Low-Current Undervoltage Lockout Mode
♦Internal 1.8A (min) Battery Switchover FET
♦Integrated Low-Battery Detect
♦Battery Short-Circuit Protection
♦Low-Cost External nMOS Overvoltage FET
♦14-Pin TDFN Package (3mm x 3mm)
MAX4919B/MAX4920B/MAX4921B
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
________________________________________________________________ Maxim Integrated Products 1
19-0614; Rev 0; 8/06
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.
MAX4919B
MAX4920B
MAX4921B
TDFN (3mm x 3mm)
TOP VIEW
245
13 11 10
ACOK
BTO
BTO
IN
BTI
BTI
1
14
ENGP1
3
12
PWR_HOLDGN1
6
9
ONOKHP_PWR
7
8
GNDPWR_ON
*EP
*EXPOSED PADDLE
+DENOTES LEAD-FREE PACKAGE
+
Pin Configuration
Ordering Information/Selector Guide
PART PIN-
PACKAGE OVLO (V) UVLO (V) TOP MARK PKG CODE
MAX4919BETD+T
14 TDFN-EP* 6.38 4.27 ABY T1433-2
MAX4920BETD+T
14 TDFN-EP* 5.80 4.27 ABZ T1433-2
MAX4921BETD+T
14 TDFN-EP* 4.65 2.35 ACA T1433-2
Note: All devices are specified over the -40°C to +85°C operating temperature range.
+Denotes lead-free package.
*EP = Exposed paddle.
MAX4919B/MAX4920B/MAX4921B
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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.
IN to GND ...............................................................-0.3V to +30V
GP1, GN1 to GND ..................................................-0.3V to +12V
IN to GP1 ................................................................-0.3V to +20V
BTO to GND ..........................................................-0.3V to +6.1V
BTI to BTO ................................................................-0.3V to +6V
BTI, ACOK, PWR_ON, EN to GND ...........................-0.3V to +6V
HP_PWR, ONOK, PWR_HOLD to GND ....................-0.3V to +6V
Continuous Power Dissipation (TA= +70°C)
14-Pin TDFN (derate 18.5mW/°C above +70°C) .......1482mW
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
ELECTRICAL CHARACTERISTICS
(VIN = 5V (MAX4919B/MAX4920B) or VIN = 4.2V (MAX4921B), VBTI = 4V, TA= -40°C to +85°C, unless otherwise noted. Typical values
are at TA= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
Input Voltage Range VIN 1.2 28 V
MAX4919B/MAX4920B 77 120
Input Supply Current IIN MAX4921B 75 110 µA
VEN = 0V; VIN = 3.9V; MAX4919B/MAX4920B
10 22
UVLO Supply Current IUVL VEN = 0V; VIN = 2.1V; MAX4921B 8 18 µA
Shutdown Supply Current ISHDN VEN = 1.6V, VIN = 3.6V 0.4 2 µA
MAX4919B/MAX4920B 4.00 4.27 4.54
V
IN Undervoltage Lockout
VUVLO
VIN falling MAX4921B
2.20 2.35 2.50
V
IN Undervoltage Lockout
Hysteresis 1%
MAX4919B
6.00 6.38 6.76
MAX4920B
5.44 5.80 6.17
Overvoltage Trip Level
VOVLO
VIN rising
MAX4921B
4.35 4.65 4.95
V
IN Overvoltage Lockout
Hysteresis 1%
BATTERY SWITCHOVER
BTI Input Range VBTI
2.30 5.50
V
BTI UVLO
VUVBTI
VBTI falling 2.0
2.15
2.3 V
BTI UVLO Hysteresis 1.5 %
BTI Low-Battery Threshold
VLVBTI
VBTI falling
2.65 2.82
3V
BTI Low-Battery Hysteresis 1.5 %
BTI Supply Current Adapter out, VPWR_HOLD = high,
EN = high 7µA
TA = +25°C2
BTI Shutdown Current VBTO = 0V
TA = -40°C to +85°C
2.8 µA
INTERNAL pFET
TA = +25°C 100
Switch On-Resistance RON VBTI = 2.7V, IBTI to
BTO = 0.5A
TA = -40°C to +85°C
120 mΩ
Forward-Overload Current Limit ILIM BTO shorted to GND 1.8 A
MAX4919B/MAX4920B/MAX4921B
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 5V (MAX4919B/MAX4920B) or VIN = 4.2V (MAX4921B), VBTI = 4V, TA= -40°C to +85°C, unless otherwise noted. Typical values
are at TA= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
GATE DRIVERS
VGN1 referenced to GND, IGN1 sourcing 1µA;
MAX4919B/MAX4920B 910
GN1 Turn-On Voltage VGN1 VGN1 referenced to GND, IGN1 sourcing 1µA;
MAX4921B 7.8 8.4
V
GN1 Pulldown Current IGPD VIN > OVLO, VGN1 = 5.5V 30 mA
GP1 Clamp Voltage
VCLAMP
VIN - VGP1 when VIN = 28V
12.5 16.5 19.5
V
GP1 Pulldown Resistor RGPD 31
51.5
72 kΩ
LOGIC INPUTS (PWR_HOLD, HP_PWR, PWR_ON, EN)
Input-High Voltage VIH VBTI = 5.50V 1.5 V
Input-Low Voltage VIL VBTI = 2.3V for PWR_HOLD, HP_PWR and
EN; VBTI = 3V for PWR_ON 0.4 V
PWR_HOLD, EN Input Leakage
Current ILKG EN, PWR_HOLD = GND or 5.5V -1 +1 µA
PWR_ON, HP_PWR Pulldown
Resistance RIPD
200
kΩ
LOGIC OUTPUTS (ACOK, ONOK)
Output-Low Voltage VOL ISINK = 1mA 0.4 V
Output-High Leakage Current 1µA
TIMING
IN Debounce Time
tINDBC
Time from UVLO < VIN < OVLO to VGN1 >
0.3V, CGN1 = 500pF 10 25 40 ms
ACOK Blanking Time
tBLNKAC
Time from VGN1 > 0.3V to ACOK low,
CGN1 = 500pF 10 25 40 ms
HP_PWR Debounce Time
tHPDBC
Time for internal pFET to turn on after
VHP_PWR > VIH 10 25 40 ms
ACOK One-Shot Time
t1SHAC
VPWR_HOLD = 0V; time for internal pFET to
turn off after ACOK < VOL (Figure 1)
488 1220 1952
ms
HP_PWR One-Shot Time
t1SHHP
VPWR_HOLD = 0V; time for internal pFET to
turn off after VHP_PWR > VIH (Figure 2)
488 1220 1952
ms
Current-Limit Blanking Time tCLIM VBTI = 2.7V; VBTO shorted to GND; time for
internal pFET current to reduce to 10mA 4 1016ms
GN1 Turn-On Time tGON
VGN1 = 0.3V to 8V
(MAX4919B/MAX4920B),
VGN1 = 0.3V to 7V (MAX4921B),
CGN1 = 500pF
10 ms
0
4
2
8
6
12
10
14
243567
GN1 GATE VOLTAGE
vs. INPUT VOLTAGE
MAX4919/20/21B toc01
INPUT VOLTAGE (V)
GN1 GATE VOLTAGE (V)
MAX4919B
VGN1 REFERENCED TO GND
0
4
2
8
6
12
10
14
2.0 3.0 3.52.5 4.0 4.5 5.0
GN1 GATE VOLTAGE
vs. INPUT VOLTAGE
MAX4919/20/21B toc02
INPUT VOLTAGE (V)
GN1 GATE VOLTAGE (V)
MAX4921B
VGN1 REFERENCED TO GND
0.5
0.8
0.7
0.6
0.9
1.0
1.1
1.2
1.3
1.4
1.5
-40 10-15 35 60 85
NORMALIZED BATTERY SWITCH RON
vs. TEMPERATURE
MAX4919/20/21B toc03
TEMPERATURE (°C)
NORMALIZED BATTERY SWITCH RON
Typical Operating Characteristics
(VBTI = 4V, TA= +25°C, unless otherwise noted.)
MAX4919B/MAX4920B/MAX4921B
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 5V (MAX4919B/MAX4920B) or VIN = 4.2V (MAX4921B), VBTI = 4V, TA= -40°C to +85°C, unless otherwise noted. Typical values
are at TA= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
GN1 Turn-Off Time tGOFF
VIN rising at 1V/µs from 5V to 8V
(MAX4919B/MAX4920B), or from 4V to 7V
(MAX4921B); VGN1 = 0.3V,
CGN1 = 500pF
620µs
Initial Overvoltage Fault Delay tOVLO VIN rising at 1V/µs from 0V to 9V, time from
VIN = 5V to IGN1 = 80% of IGPD 1.5 µs
ACOK Deassertion Delay tACOK
VIN rising at 1V/µs from 5V to 8V
(MAX4919B/MAX4920B), or from 4V to 7V
(MAX4921B); VACOK pullup
voltage = 3V; RACOK = 10kΩ (Figure 3)
5.8 µs
Disable Time tDIS VEN = 2.4V, VGN1 = 0.3V, CGN1 = 500pF 2 µs
Note 1: All specifications are 100% production tested at TA= +25°C, unless otherwise noted. Specifications over TA= -40°C to
+85°C are guaranteed by design.
MAX4919B/MAX4920B/MAX4921B
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
_______________________________________________________________________________________ 5
10ms/div
ADAPTER POWER-UP RESPONSE
VADAPTER
(5V/div)
VIN
(5V/div)
VGN1
(5V/div)
VACOK
(5V/div)
VOUT
(5V/div)
MAX4919/20/21B toc07
MAX4919B
200ms/div
ADAPTER POWER-UP RESPONSE
VADAPTER
(5V/div)
VIN
(5V/div)
VGN1
(5V/div)
VACOK
(5V/div)
VBTO
(5V/div)
MAX4919/20/21B toc08
MAX4919B
PWR_ON, HP_PWR, PWR_HOLD = 0V
2µs/div
OVERVOLTAGE RESPONSE
VADAPTER
(2V/div)
VIN
(2V/div)
VGN1
(5V/div)
VACOK
(5V/div)
MAX4919/20/21B toc09
7V
5V
7V
5V
MAX4919B
2.0
2.6
2.4
2.2
2.8
3.0
3.2
3.4
3.6
3.8
4.0
-40 10-15 35 60 85
CURRENT LIMIT
vs. TEMPERATURE
MAX4919/20/21B toc04
TEMPERATURE (°C)
CURRENT LIMIT (A)
0.980
0.985
0.990
0.995
1.000
1.005
1.010
1.015
1.020
-40 -15 10 35 60 85
NORMALIZED OVLO THRESHOLD
vs. TEMPERATURE
MAX4919/20/21B toc05
TEMPERATURE (°C)
NORMALIZED OVLO THRESHOLD
0.980
0.985
0.990
0.995
1.000
1.005
1.010
1.015
1.020
-40 -15 10 35 60 85
NORMALIZED UVLO THRESHOLD
vs. TEMPERATURE
MAX4919/20/21B toc06
TEMPERATURE (°C)
NORMALIZED UVLO THRESHOLD
Typical Operating Characteristics (continued)
(VBTI = 4V, TA= +25°C, unless otherwise noted.)
MAX4919B/MAX4920B/MAX4921B
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
6 _______________________________________________________________________________________
200ms/div
BATTERY-SWITCH TURN-ON RESPONSE
(HP_PWR RISING)
VHP_PWR
(5V/div)
VBTI
(2V/div)
VBTO
(2V/div)
IBTO
(500mA/div)
MAX4919/20/21B toc13
CBTI = CBTO = 0.1µF
2ms/div
SHORT-CIRCUIT RESPONSE
VBTI
(2V/div)
VBTO
(2V/div)
IBTO
(10A/div)
MAX4919/20/21B toc14
CBTI = 47µF
CBTO = 0.1µF
Typical Operating Characteristics (continued)
(VBTI = 4V, TA= +25°C, unless otherwise noted.)
1µs/div
UNDERVOLTAGE RESPONSE
VADAPTER
(2V/div)
VIN
(2V/div)
VGN1
(5V/div)
VACOK
(5V/div)
MAX4919/20/21B toc10
5V
3V
5V
3V
MAX4919B
1ms/div
BATTERY-SWITCH TURN-ON RESPONSE
(PWR_ON RISING)
VPWR_ON
(5V/div)
VONK
(5V/div)
VBTI
(2V/div)
IBTI
(500mA/div)
MAX4919/20/21B toc11
CBTI = CBTO = 0.1µF
1ms/div
BATTERY-SWITCH TURN-OFF RESPONSE
(PWR_ON FALLING)
VPWR_ON
(5V/div)
VONOK
(5V/div)
VBTO
(2V/div)
IBTO
(500mA/div)
MAX4919/20/21B toc12
CBTI = CBTO = 0.1µF
400ms/div
BATTERY SWITCH TURN-ON RESPONSE
(PWR_ON AND PWR_HOLD RISING)
PWR_ON
(5V/div)
PWR_HOLD
(5V/div)
IBTO
(500mA/div)
MAX4919/20/21B toc15
VBTO
(2V/div)
Detailed Description
Undervoltage Lockout (UVLO)
The MAX4919B/MAX4920B have a 4.27V (typ) under-
voltage threshold (UVLO), while the MAX4921B has
2.35V (typ) UVLO threshold. When VIN is less than
UVLO, GN1 is held low and ACOK is high impedance.
Overvoltage Lockout Thresholds (OVLO)
The MAX4919B has a 6.38V (typ) overvoltage threshold
(OVLO), the MAX4920B has a 5.8V (typ) typical OVLO,
and the MAX4921B has a 4.65V (typ) OVLO. When VIN
is greater than OVLO, GN1 is held low and ACOK is
high impedance.
Powering the MAX4919B/
MAX4920B/MAX4921B
BTI powers the MAX4919B/MAX4920B/MAX4921B inter-
nal circuitry. BTI also connects internally to a 1.8A (min)
pFET that conducts an external load to the battery using
the BTO output. See the Battery Switchover section.
GP1 Driver
When the input voltage goes above ground, GP1 pulls
low and turns on the pFET. An internal clamp protects
the pFET by insuring that the GP1 to IN voltage does
not exceed 19.5V when the input (IN) rises to 28V.
MAX4919B/MAX4920B/MAX4921B
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
_______________________________________________________________________________________ 7
Pin Description
PIN NAME FUNCTION
1 GP1 p-Channel MOSFET Gate-Drive Output. GP1 pulls the external pFET gate down when the input is above
ground.
2IN
Voltage Input. IN powers the charge pump required to turn on GN1. When the correct adapter is
plugged in, a one-shot turns on the internal pFET for 1.2s, allowing time for the microprocessor (µP) to
power-up and drive PWR_HOLD high. Bypass IN with a minimum 1µF ceramic capacitor as close as
possible to the device for ±15kV ESD protection. When operating the
MAX4919B/MAX4920B/MAX4921B with an external pFET at GP1, place the 1µF capacitor to GND as
close to the drain of the pFET as possible for the ±15kV ESD protection. If ±15kV ESD protection is not
required, place a minimum 0.1µF capacitor at IN to GND.
3 GN1 n-Channel MOSFET Gate-Drive Output. GN1 is the output of an on-chip charge pump. When VUVLO <
VIN < VOVLO, GN1 is driven above the source voltage to turn on the external n-channel MOSFET.
4, 5 BTI Battery Switch Input. BTI powers the internal circuitry. Bypass BTI with a 0.1µF capacitor. Both BTI
inputs must be externally connected together.
6
HP_PWR
Car-Kit Detection Input. When a car kit is plugged into HP_PWR, a one-shot turns on the internal pFET
for 1.2s, allowing time for the µP to power-up and drive PWR_HOLD high.
7
PWR_ON
Power-On Input. Drive PWR_ON high to turn on the internal pFET. The inverse of the PWR_ON logic
state is represented at the ONOK logic output.
8 GND Ground
9ONOK Open-Drain PWR_ON Indicator Output. ONOK is a logic output with the inverse state of the PWR_ON
input.
10, 11 BTO Battery Switch Output. Both BTO outputs must be externally connected together.
12
PWR_HOLD
Power-Hold Input. Drive PWR_HOLD high to turn on internal pFET.
13 ACOK Open-Drain Adapter Voltage Indicator Output. ACOK pulls low when the adapter voltage is stable
between UVLO and OVLO for 25ms. Connect a pullup resistor from ACOK to a logic supply.
14 EN Enable Input. Drive EN low for normal operation. Drive EN high to turn off the external MOSFETs and
enter shutdown mode.
EP —Exposed Paddle. Connect EP to ground.
MAX4919B/MAX4920B/MAX4921B
GN1 Driver
An internal 5.5V supply powers the on-chip charge
pump used to drive GN1 above IN, allowing the use of
a low-cost nFET. The GN1 voltage is approximately two
times VIN until VIN exceeds 5.5V, at which point, GN1
clamps to 9.5V (MAX4919B/MAX4920B) or 8.1V
(MAX4921B).
ACOK
ACOK is an active-low open-drain output that asserts
when VUVLO <VIN < VOVLO for the 25ms debounce
period. ACOK deasserts immediately to overvoltage
and undervoltage faults. Connect a pullup resistor from
ACOK to the logic I/O voltage of the host system.
PWR_ON
PWR_ON is one of the logic inputs that enables the
internal 1.8A switch. Drive PWR_ON high to turn on the
internal switch. PWR_ON also controls the logic output
ONOK. The ONOK open-drain output is the inverse of
the PWR_ON input state (see Figure 5). Note that
ONOK is high impedance when VIN < VUVLO, and VBTI
< 2.82V (typ). If VBTI is greater than 2.15V (typ), but
less than 2.82V (typ), PWR_ON and ONOK are dis-
abled and ONOK pulls high. When BTI rises above
2.82V (typ) again, PWR_ON is again enabled and
ONOK goes back to its previous logic level before a
low condition at BTI (see Figure 6).
Battery Switchover
An internal 1.8A (min) pFET with a 100mΩ(typ) RON
connects BTI to the load at BTO. The internal battery
switchover FET turns on when either HP_PWR,
PWR_ON, or PWR_HOLD is high. Note that when BTI
< 2.15V, the internal switch remains inactive, regard-
less of the logic control signals.
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
8 _______________________________________________________________________________________
UVLO
OVLO
IN
ACOK
ADAPTER
VOLTAGE
ACOK
ONE-SHOT
P2
STATUS
OFF
ON
25ms DEBOUNCE PERIOD
OFF
t1SHAC
Figure 1.
ACOK
One-Shot Timing Diagram
MAX4919B/MAX4920B/MAX4921B
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
_______________________________________________________________________________________ 9
t1SHHP
tHPDBC
HP_PWR
OFF
ON
OFF
HP_PWR
ONE-SHOT
P2
STATUS
Figure 2. HP_PWR One-Shot Timing Diagram
tGOFF
VOVLO
tACOK
IN
ACOK
80% OF ACOK
PULLUP VOLTAGE
GP1
Figure 3.
ACOK
Assertion Delay Timing Diagram
GP1 GN1IN
25ms
DEBOUNCER
CHARGE
PUMP
25ms
DEBOUNCER
ONE-SHOT
ONE-SHOT
PWR_HOLD
PWR_ON
ONOK
ACOK
GND
EN
HP_PWR
BTO
BTI
P2
-CURRENT LIMIT
- BLANKING TIME
COUNTER
-ON/OFF LOGIC
ON/OFF
MAX4919B
MAX4920B
MAX4921B
Figure 4. Functional Diagram
MAX4919B/MAX4920B/MAX4921B
PWR_HOLD
PWR_HOLD controls the turn-on of the 1.8A (min) cur-
rent-limit switch (P2). When a voltage is present at IN,
and VUVLO < VIN < VOVLO for 25ms, ACOK pulls low
and issues an internal one-shot pulse that turns on P2
temporarily for 1.2s (typ). During the 1.2s one-shot peri-
od, the MAX4919B/MAX4920B/MAX4921B must see a
low-to-high transition at PWR_HOLD (and PWR_HOLD
must remain high), for P2 to remain on (see Figure 7).
P2 turns off when PWR_HOLD and PWR_ON are low,
and when the HP_PWR and ACOK internal one-shot
timers have expired.
When a voltage at IN is not present, HP_PWR controls
the turn-on of P2. Upon a low-to-high transition at
HP_PWR (and HP_PWR remaining high), the
MAX4919B/MAX4920B/MAX4921B issue an internal
HP_PWR one-shot signal that turns on P2 temporarily
for 1.2s (typ). During the 1.2s one-shot period, the
MAX4919B/MAX4920B/MAX4921B must see a low-to-
high transition at PWR_HOLD (and PWR_HOLD must
remain high) for P2 to remain on. P2 turns off when
PWR_HOLD and PWR_ON are low, and when the
HP_PWR and ACOK internal one-shot timers have
expired (see Figure 8).
Current Limiting
The MAX4919B/MAX4920B/MAX4921B feature an inter-
nal 1.8A (min) current-limiting switch (P2) at BTO. The
current limit remains in effect throughout BTI’s input
supply-voltage range.
The current limit takes care of two situations: when P2 is
initially turned on, and when P2 is already on and a
short circuit occurs (see Figure 9). When P2 is turned
on, the current can be high because BTO = 0 and a
large load capacitor needs to be charged. The protec-
tion circuit prevents the load current from exceeding
the 1.8A (min) current-limit value, and BTO will have a
smooth turn-on (the larger the capacitor, the slower the
turn-on). The 10ms blanking time avoids a false fault
assertion. At the end of the blanking time, if the device
is still limiting, a fault is asserted and P2 immediately
turns off. When the switch is already on and a short-cir-
cuit condition occurs at BTO, the device limits the cur-
rent. If the fault condition duration is greater than the
blanking time, P2 turns off.
Before P2 turns on again, any condition that is attempt-
ing to turn it on must be first removed, i.e. the one-shot
(from IN or HP_PWR) must be completed, and PWR_ON
and PWR_HOLD must be low. If the three conditions are
satisfied, P2 turns on again only if either IN or
PWR_HOLD is cycled OFF and ON.
Low-Battery Operation
The MAX4919B/MAX4920B/MAX4921B operate in low-
battery mode when the battery voltage at BTI is greater
than 2.15V but less than 2.8V (typ). In low-battery opera-
tion, PWR_ON does not influence the behavior of the
internal switch.
When an adapter and car kit are not present, the internal
switch is typically controlled by PWR_HOLD. If PWR_ON
is high (ONOK is low) and BTI falls below 2.8V, ONOK
pulls high, but the internal switch remains on since
PWR_HOLD is high. If PWR_ON is high and PWR_HOLD
is low when VBTI falls below the 2.8V threshold, the inter-
nal switch turns off immediately. Upon BTI rising above
2.8V again, PWR_ON is again enabled and ONOK goes
back to its previous logic level before a low condition at
BTI occurred.
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
10 ______________________________________________________________________________________
PWR_ON
ONOK
Figure 5.
ONOK
Timing Diagram
BT1
P2
PWR_ON
VLVBTI
VUVBTI
ON
OFF
ON
ONOK
OFF
Figure 6. BTI Falling and Rising Above Its Thresholds
Note that upon VBTI falling below the 2.15V (min) thresh-
old, the internal switch remains off, irrespective of the
control signals at HP_PWR, PWR_ON, or PWR_HOLD.
Thermal Shutdown
The MAX4919B/MAX4920B/MAX4921B feature thermal
shutdown circuitry. The internal 1.8A (min) switch turns
off when the junction temperature exceeds +135°C and
immediately goes into a fault mode. The device can be
reset upon the junction temperature dropping below
+125°C. Before P2 can be turned on again, any condi-
tion that is attempting to turn it on must be first removed,
i.e., the one-shot (from IN or HP_PWR) must be complet-
ed, and PWR_ON and PWR_HOLD must be low. If the
three conditions are satisfied, P2 turns on again only if
either IN or PWR_HOLD is cycled OFF and ON.
Applications Information
MOSFET Configuration
The MAX4919B/MAX4920B/MAX4921B can drive either a
single n-channel or back-to-back n-channel MOSFET
(Figure 10). The back-to-back configuration will have
almost zero reverse current when the adapter is not pre-
sent or when the adapter voltage is below the undervolt-
age lockout threshold.
If reverse-current leakage is not a concern, a single
n-channel MOSFET can be used. This approach has
half the loss of the back-to-back configuration when
used with similar MOSFET types and is a lower cost
solution. Note that if the input is actually pulled low, the
output will be pulled low as well due to the parasitic
body diode in the MOSFET. If this is a concern, then
use the back-to-back configuration.
MAX4919B/MAX4920B/MAX4921B
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
______________________________________________________________________________________ 11
UVLO
OVLO
IN
PWR_HOLD
STATUS
ACOK
ADAPTER
VOLTAGE
ACOK
ONE-SHOT
P2 OFF
ON
25ms DEBOUNCE PERIOD
1.2s
ONE-SHOT
PERIOD
OFF
Figure 7. MAX4919B/MAX4920B/MAX4921B Power_Hold Waveform When Voltage at IN is Present
MAX4919B/MAX4920B/MAX4921B
MOSFET Selection
The MAX4919B/MAX4920B/MAX4921B are designed
for use with a complementary MOSFET or single
p-channel and dual back-to-back n-channel MOSFETS.
In most situations, MOSFETs with RDS(ON) specified for
a VGS of 4.5V will work well. Also, the VDS should be
30V in order for the MOSFET to withstand the full 28V IN
range of the MAX4919B/MAX4920B/MAX4921B. Table
1 shows a selection of MOSFETs which are appropriate
for use.
IN Bypass Considerations
For most applications, bypass IN to GND with a 1µF
ceramic capacitor to enable ±15kV ESD protection
(when GP1 is not utilized). If ±15kV is not required,
place a minimum 0.1µF capacitor at IN to GND. If the
power source has significant inductance due to long
lead length, take care to prevent overshoots due to the
LC tank circuit and provide protection if necessary to
prevent exceeding the +30V absolute maximum rating
at IN.
BTO Bypass Capacitor Considerations
In order to guarantee a successful startup of the inter-
nal p-channel MOSFET, use a capacitance lower than
CBTO(MAX). If the load capacitance is too large, then
current may not have enough time to charge the
capacitance and the device assumes that there is a
faulty load condition. The maximum capacitive-load
value that can be driven by BTO is obtained by the fol-
lowing formula:
where CBTO is the output capacitor at BTO, VBTI is
the battery voltage, tCLIM is the minimum current-limit
blanking time, and ICLIM is the minimum forward cur-
rent-limit value.
CIt
V
BTO MAX LIM CLIM
BTI
()
≤×
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
12 ______________________________________________________________________________________
PART CONFIGURATION/
PACKAGE
VGS (MAX)
(V)
VDS (MAX)
(V)
RON at 4.5V
(mΩ)MANUFACTURER
30 143
(N-FET)
Si5504DC Complementary
MOSFET/1206-8 ±20
-30 290
(P-FET)
Si5902DC Dual/1206-8 ±20 30 143
(N-FET)
Si1426DH Single/µDFN-6 ±20 30 115
(N-FET)
Si5435DC Single/1206-8 ±20 -30 80
(P-FET)
Vishay Siliconix
www.vishay.com
FDC6561AN Dual/SSOT-6 ±20 30 145
(N-FET)
FDG315N Single/µDFN-6 ±20 30 160
(N-FET)
FDC658P Single/SSOT-6 ±20 -30 75
(P-FET)
FDC654P Single/SSOT-6 ±20 -30 125
(P-FET)
Fairchild Semiconductor
www.fairchildsemi.com
Table 1. MOSFET Suggestions
Additional Applications Information
Adapter Application
Figures 11 and 12 depict the MAX4919B/MAX4920B
being utilized in an application where the AC adapter
supplies the input voltage and the car adapter is not
plugged in. In this case, when the AC adapter (5V) is
plugged in, the voltage at IN initially makes sure that a
negative voltage is not present.
If VIN remains above the UVLO and below the OVLO
ranges for more than 25ms (debouncer), the n-channel
MOSFET (N1) turns on and after 25ms, ACOK asserts
low, then a one-shot timer starts that turns P2 on for 1.2s.
During this duration, the µP needs to issue a PWR_HOLD
to keep P2 on before the one-shot period expires. The
adapter then powers the charger to charge the battery
and the battery supports the load.
Reverse-Polarity Protection
Figure 11 shows an application where the external
p-channel MOSFET is added for reverse-polarity protec-
tion. The reverse-polarity protection works by turning off
the p-channel MOSFET when the adapter voltage is
below ground. The p-channel MOSFET only turns off if
the voltage at IN is less than the threshold voltage of the
p-channel MOSFET. Due to the body diode leakage
path through the external n-channel MOSFET, the
reverse-polarity protection operation requires a reverse
current-limited load. Figure 11 shows a battery charger
as the load connected to the source of n-channel MOS-
FET. If the voltage at the load connection (source of the
n-channel MOSFET) is greater than the drop across the
n-channel MOSFET’s body diode plus the p-channel
MOSFET threshold voltage, then the p-channel MOSFET
remains on if the adapter voltage is below ground. If the
load has reverse-current protection, the voltage at the
load pulls down and the p-channel MOSFET turns off
limiting reverse current. If the load allows a large reverse
current, then this current flows out of the adapter input
and the reverse-polarity protection is defeated.
Car-Kit Application
Figures 13 and 14 illustrate the MAX4921B being uti-
lized when the car-kit adapter, with built-in charger, is
plugged in and connected directly to the battery.
HP_PWR goes through a 25ms debounce period and
then a 1.2s one-shot is issued.
During this one-shot period, the µP needs to issue a
PWR_HOLD to keep P2 on before the one-shot period
expires. The car kit then charges the battery and the
battery supports the load. Note that the reverse-polarity
protection p-channel MOSFET cannot be used in this
application due to the direct connection of the battery
to the source of the n-channel MOSFET.
MAX4919B/MAX4920B/MAX4921B
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
______________________________________________________________________________________ 13
t1SHHP
tHPDBC
HP_PWR
PWR_HOLD
OFF OFF
ON
P2 STATUS
HP_PWR
ONE-SHOT
Figure 8. MAX4919B/MAX4920B/MAX4921B Power_Hold
Waveform When Voltage IN is Not Present
MAX4919B/MAX4920B/MAX4921B
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
14 ______________________________________________________________________________________
VBTO
ILIM
tCLIM tCLIM
TURN-ON PHASE SHORT CIRCUIT
BTO
BTI
IP2
IP2
P2
MAX4919B
MAX4920B
MAX4921B
VONOK
Figure 9. MAX4919B/MAX4920B/MAX4921B Current-Limit Diagram
Chip Information
PROCESS: BiCMOS
MAX4919B/MAX4920B/MAX4921B
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
______________________________________________________________________________________ 15
N
OUT
VBAT
VBAT
IN GN1GP1
ACOK
ONOK
GND EN
BTO
BTI
P
OPTIONAL
CHARGER
VIO
AC
ADAPTER
0.1µF
0.1µF
PWR_HOLD
PWR_ON
DC-DC
CONVERTER
HP_PWR
1µF
MAX4919B
MAX4920B
µP
Figure 11. MAX4919B/MAX4920B Always Powered From Battery (Car-Kit Adapter Never Plugged In)
IN GN1GP1
ACOK
GND EN
BTO
BTI
NN
µP
VIO
AC
ADAPTER
0.1µF
1µF
OUTPUT
MAX4919B
MAX4920B
MAX4921B
Figure 10. Back-to-Back External MOSFET Configuration
MAX4919B/MAX4920B/MAX4921B
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
16 ______________________________________________________________________________________
UVLO
OVLO
IN
PWR_HOLD
ACOK
ACOK
ONE-SHOT
25ms DEBOUNCE PERIOD
1.2s ONE-SHOT PERIOD
PWR_ON
ONOK
P2
STATUS
OFF
ON
OFF
ON
Figure 12. MAX4919B/MAX4920B Timing Diagram For Non-Car-Kit Adapter Application
MAX4919B/MAX4920B/MAX4921B
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
______________________________________________________________________________________ 17
PWR_HOLD
HP_PWR
HP_PWR
ONE-SHOT
P2
STATUS
OFF
ON
25ms DEBOUNCE PERIOD
1.2s
ONE-SHOT PERIOD
OFF
PWR_ON
ONOK
ON
Figure 14. Timing Diagram For Car-Kit Adapter Application
IN GN1GP1
ONOK
GND EN
BTO
BTI
N
CAR KIT
WITH CHARGER
VIO
0.1µF
PWR_HOLD
NOR'd
OUTPUT
PWR_ON
HP_PWR
1µF
MAX4921B
DC-DC
CONVERTER
P2
VBAT
VBAT
µP
Figure 13. MAX4920B With Car-Kit Adapter and Built-In Charger Connected
MAX4919B/MAX4920B/MAX4921B
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
18 ______________________________________________________________________________________
VBAT
VBAT
µP
IN GN1GP1
ACOK
ONOK
GND EN
BTO
BTI
N
VIO
ADAPTER AND
CHARGER CIRCUITRY
0.1µF
1µF
PWR_HOLD
PWR_ON
DC-DC
CONVERTER
HP_PWR
OUT
MAX4921B
Typical Operating Circuits
N
OUT
VBAT
VBAT
IN GN1GP1
OPTIONAL
ACOK
ONOK
GND EN
BTO
BTI
P
CHARGER
VIO
AC
ADAPTER
0.1µF
0.1µF
PWR_HOLD
PWR_ON
DC-DC
CONVERTER
HP_PWR
1µF
MAX4919B
MAX4920B
µP
MAX4919B/MAX4920B/MAX4921B
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 19
© 2006 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
6, 8, &10L, DFN THIN.EPS
H
1
2
21-0137
PACKAGE OUTLINE, 6,8,10 & 14L,
TDFN, EXPOSED PAD, 3x3x0.80 mm
COMMON DIMENSIONS
SYMBOL MIN. MAX.
A 0.70 0.80
D 2.90 3.10
E 2.90 3.10
A1 0.00 0.05
L 0.20 0.40
PKG. CODE N D2 E2 eJEDEC SPEC b[(N/2)-1] x e
PACKAGE VARIATIONS
0.25 MIN.k
A2 0.20 REF.
2.30–0.101.50–0.106T633-1 0.95 BSC MO229 / WEEA 1.90 REF0.40–0.05
1.95 REF0.30–0.050.65 BSC2.30–0.108T833-1
2.00 REF0.25–0.050.50 BSC2.30–0.1010T1033-1
2.40 REF0.20–0.05- - - - 0.40 BSC1.70–0.10 2.30–0.1014T1433-1
1.50–0.10
1.50–0.10
MO229 / WEEC
MO229 / WEED-3
0.40 BSC - - - - 0.20–0.05 2.40 REFT1433-2 14 2.30–0.101.70–0.10
T633-2 6 1.50–0.10 2.30–0.10 0.95 BSC MO229 / WEEA 0.40–0.05 1.90 REF
T833-2 8 1.50–0.10 2.30–0.10 0.65 BSC MO229 / WEEC 0.30–0.05 1.95 REF
T833-3 8 1.50–0.10 2.30–0.10 0.65 BSC MO229 / WEEC 0.30–0.05 1.95 REF
-DRAWING NOT TO SCALE- H
2
2
21-0137
PACKAGE OUTLINE, 6,8,10 & 14L,
TDFN, EXPOSED PAD, 3x3x0.80 mm
2.30–0.10 MO229 / WEED-3 2.00 REF0.25–0.05
0.50 BSC
1.50–0.1010T1033-2