MAX4919B [MAXIM]
Battery Power-Up Logic with Overvoltage and Overcurrent Protection;
| 型号： | MAX4919B |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Battery Power-Up Logic with Overvoltage and Overcurrent Protection 电池 |
| 文件： | 总19页 (文件大小：317K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0614; Rev 0; 8/06
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
General Description
Features
The MAX4919B/MAX4920B/MAX4921B overvoltage
protection controllers protect low-voltage systems
against high-voltage faults up to +28V. An internal 1.8A
ꢀ Input Overvoltage Protection Up to +28V
ꢀ Preset Overvoltage Protection Trip Level
6.38V (MAX4919B)
(min) pFET with low R
(100mΩ) switches a battery to
ON
5.80V (MAX4920B)
4.65V (MAX4921B)
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 .
ꢀ Adapter/Car-Kit Auto-Selector
ꢀ Low-Current Undervoltage Lockout Mode
ꢀ Internal 1.8A (min) Battery Switchover FET
ꢀ Integrated Low-Battery Detect
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.
ꢀ Battery Short-Circuit Protection
ꢀ Low-Cost External nMOS Overvoltage FET
ꢀ 14-Pin TDFN Package (3mm x 3mm)
Pin Configuration
TOP VIEW
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.
14 13 12 11 10
9
8
Applications
Cell Phones
MAX4919B
MAX4920B
MAX4921B
Digital Still Cameras
PDAs and Palmtop Devices
MP3 Players
*EP
+
1
2
3
4
5
6
7
TDFN (3mm x 3mm)
*EXPOSED PADDLE
+DENOTES LEAD-FREE PACKAGE
Ordering Information/Selector Guide
PIN-
PACKAGE
PART
OVLO (V)
UVLO (V)
TOP MARK
PKG CODE
MAX4919BETD+T
MAX4920BETD+T
MAX4921BETD+T
14 TDFN-EP*
14 TDFN-EP*
14 TDFN-EP*
6.38
5.80
4.65
4.27
4.27
2.35
ABY
ABZ
ACA
T1433-2
T1433-2
T1433-2
Note: All devices are specified over the -40°C to +85°C operating temperature range.
+Denotes lead-free package.
*EP = Exposed paddle.
________________________________________________________________ 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.
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
ABSOLUTE MAXIMUM RATINGS
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 (T = +70°C)
A
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
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 = 5V (MAX4919B/MAX4920B) or V = 4.2V (MAX4921B), V
= 4V, T = -40°C to +85°C, unless otherwise noted. Typical values
A
IN
IN
BTI
are at T = +25°C.) (Note 1)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
28
UNITS
Input Voltage Range
V
1.2
V
IN
MAX4919B/MAX4920B
MAX4921B
77
75
120
110
22
Input Supply Current
I
µA
µA
IN
V
V
V
= 0V; V = 3.9V; MAX4919B/MAX4920B
10
EN
EN
EN
IN
UVLO Supply Current
I
UVL
= 0V; V = 2.1V; MAX4921B
8
18
IN
Shutdown Supply Current
IN Undervoltage Lockout
I
= 1.6V, V = 3.6V
0.4
4.27
2.35
2
µA
V
SHDN
IN
MAX4919B/MAX4920B
MAX4921B
4.00
2.20
4.54
2.50
V
V
falling
UVLO
IN
IN
V
IN Undervoltage Lockout
Hysteresis
1
%
V
MAX4919B
6.00
5.44
4.35
6.38
5.80
4.65
6.76
6.17
4.95
Overvoltage Trip Level
V
V
rising
MAX4920B
MAX4921B
OVLO
IN Overvoltage Lockout
Hysteresis
1
%
BATTERY SWITCHOVER
BTI Input Range
V
2.30
2.0
5.50
2.3
V
V
BTI
BTI UVLO
V
V
V
falling
falling
2.15
1.5
UVBTI
BTI
BTI
BTI UVLO Hysteresis
BTI Low-Battery Threshold
BTI Low-Battery Hysteresis
%
V
V
2.65
2.82
1.5
3
LVBTI
%
Adapter out, V
EN = high
= high,
PWR_HOLD
BTI Supply Current
7
µA
µA
T
A
= +25°C
2
BTI Shutdown Current
INTERNAL pFET
V
= 0V
BTO
T
A
= -40°C to +85°C
2.8
T
T
= +25°C
100
120
A
V
= 2.7V, I
= 0.5A
BTI
BTI to
Switch On-Resistance
Forward-Overload Current Limit
R
mΩ
ON
BTO
= -40°C to +85°C
A
I
BTO shorted to GND
1.8
A
LIM
2
_______________________________________________________________________________________
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
ELECTRICAL CHARACTERISTICS (continued)
(V = 5V (MAX4919B/MAX4920B) or V = 4.2V (MAX4921B), V
= 4V, T = -40°C to +85°C, unless otherwise noted. Typical values
A
IN
IN
BTI
are at T = +25°C.) (Note 1)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
GATE DRIVERS
V
referenced to GND, I
sourcing 1µA;
sourcing 1µA;
GN1
GN1
9
10
MAX4919B/MAX4920B
GN1 Turn-On Voltage
V
V
GN1
V
referenced to GND, I
GN1
GN1
7.8
8.4
MAX4921B
GN1 Pulldown Current
GP1 Clamp Voltage
GP1 Pulldown Resistor
I
V
V
> OVLO, V
= 5.5V
GN1
30
mA
V
GPD
IN
IN
V
- V
when V = 28V
12.5
31
16.5
51.5
19.5
72
CLAMP
GP1
IN
R
kΩ
GPD
LOGIC INPUTS (PWR_HOLD, HP_PWR, PWR_ON, EN)
Input-High Voltage
V
V
= 5.50V
1.5
V
V
IH
BTI
V
= 2.3V for PWR_HOLD, HP_PWR and
= 3V for PWR_ON
BTI
Input-Low Voltage
V
0.4
+1
IL
EN; V
BTI
PWR_HOLD, EN Input Leakage
Current
I
EN, PWR_HOLD = GND or 5.5V
-1
µA
LKG
PWR_ON, HP_PWR Pulldown
Resistance
R
IPD
200
kΩ
LOGIC OUTPUTS (ACOK, ONOK)
Output-Low Voltage
V
I
= 1mA
0.4
1
V
OL
SINK
Output-High Leakage Current
TIMING
µA
Time from UVLO < V < OVLO to V
>
IN
GN1
IN Debounce Time
t
10
10
25
25
40
40
ms
ms
ms
ms
ms
ms
INDBC
0.3V, C
= 500pF
GN1
Time from V
> 0.3V to ACOK low,
GN1
ACOK Blanking Time
HP_PWR Debounce Time
ACOK One-Shot Time
HP_PWR One-Shot Time
Current-Limit Blanking Time
t
BLNKAC
C
= 500pF
GN1
Time for internal pFET to turn on after
t
10
25
40
HPDBC
V
> V
IH
HP_PWR
V
= 0V; time for internal pFET to
PWR_HOLD
t
488
488
4
1220
1220
10
1952
1952
16
1SHAC
1SHHP
turn off after ACOK < V (Figure 1)
OL
V
= 0V; time for internal pFET to
PWR_HOLD
t
turn off after V
> V (Figure 2)
IH
HP_PWR
V
= 2.7V; V
shorted to GND; time for
BTO
BTI
t
CLIM
internal pFET current to reduce to 10mA
V
= 0.3V to 8V
GN1
(MAX4919B/MAX4920B),
GN1 Turn-On Time
t
10
ms
GON
V
= 0.3V to 7V (MAX4921B),
= 500pF
GN1
C
GN1
_______________________________________________________________________________________
3
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
ELECTRICAL CHARACTERISTICS (continued)
(V = 5V (MAX4919B/MAX4920B) or V = 4.2V (MAX4921B), V
= 4V, T = -40°C to +85°C, unless otherwise noted. Typical values
A
IN
IN
BTI
are at T = +25°C.) (Note 1)
A
PARAMETER
SYMBOL
CONDITIONS
rising at 1V/µs from 5V to 8V
MIN
TYP
MAX
UNITS
V
IN
(MAX4919B/MAX4920B), or from 4V to 7V
(MAX4921B); V = 0.3V,
GN1 Turn-Off Time
t
6
20
µs
GOFF
OVLO
ACOK
GN1
C
= 500pF
GN1
V
V
rising at 1V/µs from 0V to 9V, time from
IN
IN
Initial Overvoltage Fault Delay
t
1.5
µs
= 5V to I
= 80% of I
GPD
GN1
V
rising at 1V/µs from 5V to 8V
IN
(MAX4919B/MAX4920B), or from 4V to 7V
ACOK Deassertion Delay
t
5.8
2
µs
µs
(MAX4921B); V
voltage = 3V; R
pullup
= 10kΩ (Figure 3)
ACOK
ACOK
Disable Time
t
V
= 2.4V, V
= 0.3V, C
= 500pF
DIS
EN
GN1
GN1
Note 1: All specifications are 100% production tested at T = +25°C, unless otherwise noted. Specifications over T = -40°C to
A
A
+85°C are guaranteed by design.
Typical Operating Characteristics
(V
= 4V, T = +25°C, unless otherwise noted.)
BTI
A
GN1 GATE VOLTAGE
vs. INPUT VOLTAGE
GN1 GATE VOLTAGE
vs. INPUT VOLTAGE
NORMALIZED BATTERY SWITCH R
vs. TEMPERATURE
ON
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
14
12
10
8
14
MAX4919B
REFERENCED TO GND
MAX4921B
REFERENCED TO GND
V
V
GN1
GN1
12
10
8
6
6
4
4
2
2
0
0
2
3
4
5
6
7
2.0
2.5
3.0
3.5
4.0
4.5
5.0
-40
-15
10
35
60
85
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
TEMPERATURE (°C)
4
_______________________________________________________________________________________
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
Typical Operating Characteristics (continued)
(V
= 4V, T = +25°C, unless otherwise noted.)
A
BTI
NORMALIZED OVLO THRESHOLD
vs. TEMPERATURE
CURRENT LIMIT
vs. TEMPERATURE
4.0
3.8
3.6
3.4
3.2
3.0
2.8
2.6
2.4
2.2
2.0
1.020
1.015
1.010
1.005
1.000
0.995
0.990
0.985
0.980
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
NORMALIZED UVLO THRESHOLD
vs. TEMPERATURE
ADAPTER POWER-UP RESPONSE
MAX4919/20/21B toc07
1.020
V
ADAPTER
(5V/div)
MAX4919B
1.015
1.010
1.005
1.000
0.995
0.990
0.985
0.980
V
IN
(5V/div)
V
GN1
(5V/div)
V
ACOK
(5V/div)
V
OUT
(5V/div)
10ms/div
-40
-15
10
35
60
85
TEMPERATURE (°C)
ADAPTER POWER-UP RESPONSE
OVERVOLTAGE RESPONSE
MAX4919/20/21B toc09
MAX4919/20/21B toc08
V
ADAPTER
(5V/div)
MAX4919B
MAX4919B
7V
5V
7V
5V
V
ADAPTER
(2V/div)
V
IN
(5V/div)
V
V
IN
GN1
(2V/div)
(5V/div)
PWR_ON, HP_PWR, PWR_HOLD = 0V
V
ACOK
(5V/div)
V
GN1
(5V/div)
V
BTO
(5V/div)
V
ACOK
(5V/div)
200ms/div
2µs/div
_______________________________________________________________________________________
5
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
Typical Operating Characteristics (continued)
(V
= 4V, T = +25°C, unless otherwise noted.)
BTI
A
BATTERY-SWITCH TURN-ON RESPONSE
(PWR_ON RISING)
UNDERVOLTAGE RESPONSE
MAX4919/20/21B toc11
MAX4919/20/21B toc10
V
PWR_ON
(5V/div)
MAX4919B
C
= C = 0.1µF
BTO
BTI
5V
3V
5V
3V
V
ADAPTER
(2V/div)
V
ONK
(5V/div)
V
IN
(2V/div)
V
BTI
(2V/div)
V
GN1
(5V/div)
I
V
BTI
ACOK
(5V/div)
(500mA/div)
1ms/div
1µs/div
BATTERY-SWITCH TURN-ON RESPONSE
BATTERY-SWITCH TURN-OFF RESPONSE
(HP_PWR RISING)
(PWR_ON FALLING)
MAX4919/20/21B toc13
MAX4919/20/21B toc12
V
V
HP_PWR
(5V/div)
PWR_ON
(5V/div)
C
= C = 0.1µF
BTO
BTI
C
= C = 0.1µF
BTO
BTI
V
BTI
(2V/div)
V
ONOK
(5V/div)
V
V
BTO
(2V/div)
BTO
(2V/div)
I
I
BTO
(500mA/div)
BTO
(500mA/div)
200ms/div
1ms/div
BATTERY SWITCH TURN-ON RESPONSE
(PWR_ON AND PWR_HOLD RISING)
SHORT-CIRCUIT RESPONSE
MAX4919/20/21B toc15
MAX4919/20/21B toc14
PWR_ON
(5V/div)
V
BTI
(2V/div)
C
C
= 47µF
= 0.1µF
BTI
BTO
PWR_HOLD
(5V/div)
V
V
BTO
(2V/div)
BTO
(2V/div)
I
I
BTO
(500mA/div)
BTO
(10A/div)
400ms/div
2ms/div
6
_______________________________________________________________________________________
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
Pin Description
PIN
NAME
FUNCTION
p-Channel MOSFET Gate-Drive Output. GP1 pulls the external pFET gate down when the input is above
ground.
1
GP1
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
2
IN
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.
n-Channel MOSFET Gate-Drive Output. GN1 is the output of an on-chip charge pump. When V
<
UVLO
3
4, 5
6
GN1
BTI
V
< V
, GN1 is driven above the source voltage to turn on the external n-channel MOSFET.
OVLO
IN
Battery Switch Input. BTI powers the internal circuitry. Bypass BTI with a 0.1µF capacitor. Both BTI
inputs must be externally connected together.
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.
HP_PWR
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.
7
8
9
PWR_ON
GND
Ground
Open-Drain PWR_ON Indicator Output. ONOK is a logic output with the inverse state of the PWR_ON
input.
ONOK
10, 11
12
BTO
Battery Switch Output. Both BTO outputs must be externally connected together.
PWR_HOLD Power-Hold Input. Drive PWR_HOLD high to turn on internal pFET.
Open-Drain Adapter Voltage Indicator Output. ACOK pulls low when the adapter voltage is stable
ACOK
13
between UVLO and OVLO for 25ms. Connect a pullup resistor from ACOK to a logic supply.
Enable Input. Drive EN low for normal operation. Drive EN high to turn off the external MOSFETs and
enter shutdown mode.
14
EP
EN
—
Exposed Paddle. Connect EP to ground.
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.
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 V is less than
IN
UVLO, GN1 is held low and ACOK is high impedance.
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.
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 V
IN
is greater than OVLO, GN1 is held low and ACOK is
high impedance.
_______________________________________________________________________________________
7
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
ADAPTER
VOLTAGE
OVLO
UVLO
IN
25ms DEBOUNCE PERIOD
ACOK
t
1SHAC
ACOK
ONE-SHOT
OFF
OFF
P2
STATUS
ON
Figure 1. ACOK One-Shot Timing Diagram
GN1 Driver
ONOK. The ONOK open-drain output is the inverse of
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 V until V exceeds 5.5V, at which point, GN1
the PWR_ON input state (see Figure 5). Note that
ONOK is high impedance when V < V
, and V
BTI
IN
UVLO
< 2.82V (typ). If V
is greater than 2.15V (typ), but
BTI
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).
IN
IN
clamps to 9.5V (MAX4919B/MAX4920B) or 8.1V
(MAX4921B).
ACOK
ACOK is an active-low open-drain output that asserts
when V
<V < V
for the 25ms debounce
OVLO
Battery Switchover
UVLO
IN
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.
An internal 1.8A (min) pFET with a 100mΩ (typ) R
ON
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.
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
8
_______________________________________________________________________________________
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
V
OVLO
IN
HP_PWR
t
HPDBC
t
1SHHP
GP1
HP_PWR
ONE-SHOT
t
GOFF
OFF
OFF
P2
STATUS
t
ACOK
ON
80% OF ACOK
PULLUP VOLTAGE
ACOK
Figure 2. HP_PWR One-Shot Timing Diagram
Figure 3. ACOK Assertion Delay Timing Diagram
EN
GP1
IN
GN1
BTI
25ms
DEBOUNCER
CHARGE
PUMP
ACOK
ONOK
P2
ONE-SHOT
ON/OFF
-CURRENT LIMIT
- BLANKING TIME
COUNTER
PWR_ON
ONE-SHOT
PWR_HOLD
-ON/OFF LOGIC
BTO
MAX4919B
MAX4920B
MAX4921B
25ms
DEBOUNCER
HP_PWR
GND
Figure 4. Functional Diagram
_______________________________________________________________________________________
9
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
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 V
< V < V
for 25ms, ACOK pulls low
OVLO
UVLO
IN
PWR_ON
ONOK
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.
Figure 5. ONOK Timing Diagram
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).
BT1
V
LVBTI
V
UVBTI
PWR_ON
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.
ONOK
OFF
OFF
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.
ON
ON
P2
Figure 6. BTI Falling and Rising Above Its Thresholds
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
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.
is low when V
falls below the 2.8V threshold, the inter-
BTI
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.
10 ______________________________________________________________________________________
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
ADAPTER
VOLTAGE
OVLO
UVLO
IN
25ms DEBOUNCE PERIOD
ACOK
1.2s
ONE-SHOT
PERIOD
ACOK
ONE-SHOT
PWR_HOLD
STATUS
OFF
OFF
P2
ON
Figure 7. MAX4919B/MAX4920B/MAX4921B Power_Hold Waveform When Voltage at IN is Present
Note that upon V
old, the internal switch remains off, irrespective of the
control signals at HP_PWR, PWR_ON, or PWR_HOLD.
falling below the 2.15V (min) thresh-
BTI
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.
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.
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.
______________________________________________________________________________________ 11
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
Table 1. MOSFET Suggestions
CONFIGURATION/
PACKAGE
V (MAX)
GS
(V)
V (MAX)
DS
(V)
R
at 4.5V
ON
(mΩ)
PART
MANUFACTURER
143
(N-FET)
30
Complementary
MOSFET/1206-8
Si5504DC
20
290
(P-FET)
-30
30
143
(N-FET)
Vishay Siliconix
www.vishay.com
Si5902DC
Si1426DH
Si5435DC
FDC6561AN
FDG315N
FDC658P
FDC654P
Dual/1206-8
Single/µDFN-6
Single/1206-8
Dual/SSOT-6
Single/µDFN-6
Single/SSOT-6
Single/SSOT-6
20
20
20
20
20
20
20
115
(N-FET)
30
80
(P-FET)
-30
30
145
(N-FET)
160
(N-FET)
30
Fairchild Semiconductor
www.fairchildsemi.com
75
(P-FET)
-30
-30
125
(P-FET)
MOSFET Selection
BTO Bypass Capacitor Considerations
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 order to guarantee a successful startup of the inter-
nal p-channel MOSFET, use a capacitance lower than
C
. If the load capacitance is too large, then
BTO(MAX)
In most situations, MOSFETs with R
specified for
DS
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:
DS(ON)
a V
of 4.5V will work well. Also, the V
should be
GS
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.
I
× t
LIM CLIM
C
≤
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(MAX)
V
BTI
where C
is the output capacitor at BTO, V
is
BTI
BTO
the battery voltage, t
blanking time, and I
rent-limit value.
is the minimum current-limit
is the minimum forward cur-
CLIM
CLIM
12 ______________________________________________________________________________________
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
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
HP_PWR
t
below ground. The p-channel MOSFET only turns off if
HPDBC
the voltage at IN is less than the threshold voltage of the
p-channel MOSFET. Due to the body diode leakage
t
1SHHP
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.
HP_PWR
ONE-SHOT
OFF
OFF
P2 STATUS
ON
PWR_HOLD
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.
Figure 8. MAX4919B/MAX4920B/MAX4921B Power_Hold
Waveform When Voltage IN is Not Present
Additional Applications Information
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.
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 V remains above the UVLO and below the OVLO
IN
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.
______________________________________________________________________________________ 13
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
TURN-ON PHASE
SHORT CIRCUIT
MAX4919B
MAX4920B
MAX4921B
BTI
P2
V
BTO
I
P2
BTO
I
LIM
I
P2
t
t
CLIM
CLIM
V
ONOK
Figure 9. MAX4919B/MAX4920B/MAX4921B Current-Limit Diagram
Chip Information
PROCESS: BiCMOS
14 ______________________________________________________________________________________
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
N
N
OUTPUT
AC
ADAPTER
1µF
V
IO
GP1
IN
GN1
BTI
0.1µF
MAX4919B
MAX4920B
MAX4921B
µP
ACOK
BTO
GND
EN
Figure 10. Back-to-Back External MOSFET Configuration
OPTIONAL
P
N
OUT
AC
ADAPTER
CHARGER
1µF
0.1µF
V
IO
GP1
IN
GN1
BTI
0.1µF
V
BAT
MAX4919B
MAX4920B
ACOK
ONOK
µP
DC-DC
CONVERTER
BTO
PWR_HOLD
PWR_ON
GND
EN
HP_PWR
V
BAT
Figure 11. MAX4919B/MAX4920B Always Powered From Battery (Car-Kit Adapter Never Plugged In)
______________________________________________________________________________________ 15
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
OVLO
UVLO
IN
25ms DEBOUNCE PERIOD
ACOK
1.2s ONE-SHOT PERIOD
ACOK
ONE-SHOT
PWR_HOLD
OFF
OFF
P2
STATUS
ON
ON
PWR_ON
ONOK
Figure 12. MAX4919B/MAX4920B Timing Diagram For Non-Car-Kit Adapter Application
16 ______________________________________________________________________________________
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
N
1µF
V
IO
GP1
IN
GN1
BTI
CAR KIT
WITH CHARGER
MAX4921B
P2
0.1µF
V
BAT
NOR'd
OUTPUT
ONOK
µP
PWR_HOLD
PWR_ON
DC-DC
CONVERTER
BTO
HP_PWR
GND
EN
V
BAT
Figure 13. MAX4920B With Car-Kit Adapter and Built-In Charger Connected
HP_PWR
25ms DEBOUNCE PERIOD
HP_PWR
1.2s
ONE-SHOT
ONE-SHOT PERIOD
PWR_HOLD
PWR_ON
ONOK
OFF
P2
OFF
STATUS
ON
ON
Figure 14. Timing Diagram For Car-Kit Adapter Application
______________________________________________________________________________________ 17
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
Typical Operating Circuits
N
OUT
ADAPTER AND
CHARGER CIRCUITRY
1µF
V
IO
GP1
IN
GN1
BTI
0.1µF
V
BAT
ACOK
MAX4921B
µP
DC-DC
CONVERTER
ONOK
BTO
PWR_HOLD
PWR_ON
GND
EN
HP_PWR
V
BAT
OPTIONAL
P
N
OUT
AC
ADAPTER
CHARGER
0.1µF
1µF
V
IO
GP1
IN
GN1
BTI
0.1µF
V
BAT
MAX4919B
MAX4920B
ACOK
ONOK
µP
DC-DC
CONVERTER
BTO
PWR_HOLD
PWR_ON
GND
EN
HP_PWR
V
BAT
18 ______________________________________________________________________________________
Battery Power-Up Logic with Overvoltage
and Overcurrent Protection
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.)
PACKAGE OUTLINE, 6,8,10 & 14L,
TDFN, EXPOSED PAD, 3x3x0.80 mm
1
H
21-0137
2
PACKAGE VARIATIONS
COMMON DIMENSIONS
MIN. MAX.
SYMBOL
PKG. CODE
T633-1
N
6
D2
1.50–0.10 2.30–0.10 0.95 BSC
1.50–0.10 2.30–0.10
E2
e
JEDEC SPEC
MO229 / WEEA
MO229 / WEEA
MO229 / WEEC
MO229 / WEEC
MO229 / WEEC
b
[(N/2)-1] x e
1.90 REF
1.90 REF
1.95 REF
1.95 REF
1.95 REF
2.00 REF
2.00 REF
2.40 REF
2.40 REF
0.40–0.05
0.40–0.05
0.30–0.05
0.30–0.05
0.30–0.05
A
0.70
2.90
2.90
0.00
0.20
0.80
3.10
3.10
0.05
0.40
T633-2
6
D
E
0.95 BSC
T833-1
8
1.50–0.10 2.30–0.10 0.65 BSC
1.50–0.10 2.30–0.10 0.65 BSC
1.50–0.10 2.30–0.10 0.65 BSC
T833-2
8
A1
L
T833-3
8
T1033-1
T1033-2
T1433-1
T1433-2
10
10
14
14
1.50–0.10 2.30–0.10 0.50 BSC MO229 / WEED-3 0.25–0.05
k
0.25 MIN.
0.20 REF.
1.50–0.10 2.30–0.10
0.25–0.05
0.20–0.05
0.20–0.05
A2
0.50 BSC MO229 / WEED-3
1.70–0.10 2.30–0.10 0.40 BSC
1.70–0.10 2.30–0.10 0.40 BSC
- - - -
- - - -
PACKAGE OUTLINE, 6,8,10 & 14L,
TDFN, EXPOSED PAD, 3x3x0.80 mm
2
-DRAWING NOT TO SCALE-
H
21-0137
2
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.
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