MAXIM MAX1614

19-1176; Rev 0; 12/96
High-Side, N-Channel MOSFET
Switch Driver
____________________________Features
The MAX1614 drives high-side, N-channel power MOSFETs
to provide battery power-switching functions in portable
equipment. N-channel power MOSFETs typically have
one-third the on-resistance of P-channel MOSFETs of similar size and cost. An internal micropower regulator and
charge pump generate the high-side drive output voltage,
while requiring no external components.
♦ Internal On/Off Latch
The MAX1614 also features a 1.5%-accurate low-battery
comparator that can be used to indicate a low-battery
condition, provide an early power-fail warning to the system microprocessor, or disconnect the battery from the
load, preventing deep discharge and battery damage. An
internal latch allows for pushbutton on/off control with very
low current consumption. Off-mode current consumption
is only 6µA while normal operation requires less than
25µA. The MAX1614 is available in the space-saving
µMAX package that occupies about 60% less space than
a standard 8-pin SO.
♦ 1.5%-Accurate Low-Battery Detector
________________________Applications
Notebook Computers
♦ High-Side, N-Channel Power MOSFET Drive
♦ 25µA (max) Quiescent Current
♦ 6µA (max) Off Current
♦ Requires No External Components
♦ Space-Saving µMAX Package
♦ 5V to 26V Input Voltage Range
♦ Drives Single or Back-to-Back MOSFETs
♦ Controlled Turn-On for Low Inrush Current
______________Ordering Information
PART
MAX1614C/D
Portable Equipment
TEMP. RANGE
PIN-PACKAGE
0°C to +70°C
Dice*
MAX1614EUA
-40°C to +85°C
*Contact factory for dice specifications.
Hand-Held Instruments
Battery Packs
8 µMAX
__________Typical Operating Circuit
N
N
LOAD
__________________Pin Configuration
OPTIONAL FOR
REVERSE CURRENT
PROTECTION
GATE
TOP VIEW
SRC
ON
BATT
MAX1614
OFF
R1
ON 1
8
BATT
OFF 2
7
SRC
6
GATE
5
GND
LBO 3
MAX1614
LBI 4
LBO
LBI
µMAX
R2
GND
________________________________________________________________ Maxim Integrated Products
1
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MAX1614
_______________General Description
MAX1614
High-Side, N-Channel MOSFET
Switch Driver
ABSOLUTE MAXIMUM RATINGS
BATT, SRC to GND.................................................-0.3V to +30V
GATE to SRC ..........................................................-0.3V to +12V
GATE to GND .........................................................-0.3V to +36V
GATE + SRC Sink Current, Continuous .............................2.7mA
LBI, LBO, ON, OFF to GND....................................-0.3V to +12V
LBO Current ..........................................................................5mA
Continuous Power Dissipation (TA = +70°C)
µMAX (derate 4.10mV/°C above +70°C) .....................330mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+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
(VBATT = 15V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
UNITS
26
V
BATT Operating Range
VGATE - VSRC > 3V, SRC = BATT
BATT Shutdown Current
VBATT = 26V, ON = OFF = unconnected,
IGATE = 0A, device latched off, VLBI = 1.5V
4
7
µA
VBATT = 15V, ON = OFF = unconnected,
IGATE = 0A, device latched on, VLBI = 1.5V,
SRC = BATT
17
30
µA
Quiescent Current
ISHDN
IBATT +
ISRC
5
MAX
µA
VBATT = 26V, ON = OFF = unconnected,
IGATE = 0A, device latched on, VLBI = 1.5V,
SRC = BATT
21
40
8
9.0
INTERNAL CHARGE PUMP
GATE Drive Voltage
VGS
Measured from GATE to SRC, VBATT = 15V,
IGATE = 0A
6.5
V
Measured from GATE to SRC, VBATT = VSRC = 5V,
IGATE = 1.5µA
3
GATE Drive Output Current
VGATE = VSRC = 15V
15
60
µA
GATE Discharge Current
VGATE = 4V, device latched off
0.5
2
mA
1.218
V
LOW-BATTERY COMPARATOR
LBI Trip Level
VTH
LBI input falling
1.182
LBI Trip Hysteresis
1.20
0.02VTH
Minimum VBATT for Valid LBO
Tested at VLBI = VBATT / 4
0.9
V
4
V
nA
LBI Input Current
ILBI
VLBI = 1.3V
10
LBO Low Voltage
VOL
ISINK = 1mA
0.4
V
LBO High Leakage
VOH
VLBO = 11.5V
0.5
µA
CONTROL INPUTS (ON, OFF)
Minimum Input Pull-Up Current
Tested at 2V
Maximum Input Pull-Up Current
Tested at 0.6V
Input Low Voltage
VIL
VBATT = 5V
Input High Voltage
VIH
VBATT = 26V
Minimum Input Pulse Width
tPW
VBATT = 5V
2
0.5
µA
1.5
2
µA
0.6
V
1.0
µs
2.0
V
0.5
_______________________________________________________________________________________
High-Side, N-Channel MOSFET
Switch Driver
(VBATT = 15V, TA = -40°C to +85°C, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
BATT Operating Range
CONDITIONS
MIN
VGATE - VSRC > 3V, SRC = BATT
MAX
UNITS
26
V
ISHDN
VBATT = 26V, ON = OFF = unconnected,
IGATE = 0A, device latched off, VLBI = 1.5V
8
µA
IBATT +
ISAC
VBATT = 26V, ON = OFF = unconnected,
IGATE = 0A, device latched on, VLBI = 1.5V
40
µA
BATT Shutdown Current
Quiescent Current
TYP
5.0
INTERNAL CHARGE PUMP
GATE Drive Voltage
Measured from GATE to SRC, VBATT = 15V,
IGATE = 0A
VGS
GATE Drive Output Current
6.5
9.0
V
Measured from GATE to SRC, VBATT = 5.25V,
IGATE = 1.5µA, VSRC = 5.25V
3
VGATE = VSRC = 15V
15
60
µA
1.224
V
LOW BATTERY COMPARATOR
LOW-BATTERY
LBI Trip Level
VTH
LBI input falling
1.176
1.20
Note 1: Specifications to -40°C are guaranteed by design and not production tested.
__________________________________________Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
TA = -40°C
12
10
TA = -40°C
3.0
2.5
2.0
6
10
15
20
VBATT (V)
25
30
1.26
VLBI RISING
1.24
1.22
VLBI FALLING
1.18
1.16
1.0
5
VBATT = 15V
1.28
1.20
1.5
8
1.30
LBI THRESHOLD (V)
TA = +25°C
14
TA = +25°C
3.5
18
16
TA = +85°C
MAX1614-02
TA = +85°C
SHUTDOWN CURRENT (µA)
SUPPLY CURRENT (µA)
20
4.0
MAX1614-01
22
LOW-BATTERY THRESHOLD
vs. TEMPERATURE
OFF SUPPLY CURRENT
vs. VBATT
MAX1614-05
ON SUPPLY CURRENT
vs. VBATT
5
10
15
20
VBATT (V)
25
30
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
_______________________________________________________________________________________
3
MAX1614
ELECTRICAL CHARACTERISTICS
____________________________Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
GATE-CHARGING CURRENT
vs. TEMPERATURE
TA = +85°C
1.5
1.0
0.5
0
30
32
31
30
29
28
27
0
2
4
6
8
-40
10 12 14 16 18 20
29
TA = +85°C
28
27
TA = -40°C
26
25
24
23
26
-0.5
MAX1614-06
VBATT = 15V
33
-20
0
20
40
60
80
100
22
5
10
15
TEMPERATURE (°C)
VGATE (V)
GATE AND SOURCE TRANSITIONS
FOR TYPICAL MOSFET LOAD
25
30
MAX1614-07
GATE TURN-ON TRANSITION
FOR TYPICAL MOSFET LOAD
VGATE
VSRC
VGATE
Si9936 MOSFETS
ILOAD = 1A
ON = GND
VSRC
5V/div
5V/div
0V
VOFF
0V
VOFF
100µs/div
1ms/div
MAX1614-09
GATE TURN-OFF TRANSITION
FOR TYPICAL MOSFET LOAD
VGATE
Si9936 MOSFETS
ILOAD = 1A
Ciss = 400pF
ON = GND
VSRC
5V/div
VOFF
20µs/div
4
20
VBATT (V)
_______________________________________________________________________________________
MAX1614-08
TA = +25°C
34
GATE-CHARGING CURRENT (µA)
2.0
GATE-CHARGING CURRENT
vs. BATT VOLTAGE
MAX1614--03
TA = -40°C
GATE-CHARGING CURRENT (µA)
2.5
MAX1614-04
GATE-DISCHARGE CURRENT
vs. GATE VOLTAGE
GATE-DISCHARGE CURRENT (mA)
MAX1614
High-Side, N-Channel MOSFET
Switch Driver
Si9936 MOSFETS
ILOAD = 1A
Ciss = 400pF
ON = GND
High-Side, N-Channel MOSFET
Switch Driver
PIN
NAME
FUNCTION
1
ON
SET Input to the On/Off Latch. Pulse ON low with OFF high to turn on the external MOSFET switch. When
both ON and OFF are low, the part is off.
2
OFF
RESET Input to the On/Off Latch. Pulse OFF low with ON high to turn off the external MOSFET switch. When
both ON and OFF are low, the part is off.
3
LBO
Open-Drain, Low-Battery Comparator Output. LBO is low when VLBI is below the trip point.
4
LBI
Low-Battery Comparator Input. LBO goes low when VLBI falls below 1.20V (typ). Connect a voltage divider
between BATT, LBI, and GND to set the battery undervoltage trip threshold (see Typical Operating Circuit).
5
GND
System Ground
6
GATE
Gate-Drive Output. Connect to the gates of external, N-channel MOSFETs. When the MAX1614 is off, GATE
actively pulls to GND.
7
SRC
Source Input. Connect to the sources of external, N-channel MOSFETs. When the MAX1614 is off, SRC
actively pulls to GND.
8
BATT
Battery Input. Connect to a battery voltage between 5V and 26V.
_______________Detailed Description
The MAX1614 uses an internal, monolithic charge pump
and low-dropout linear regulator to supply the required
8V VGS voltage to fully enhance an N-channel MOSFET
high-side switch (Figure 1). The charge pump typically
supplies 30µA, charging 800pF of gate capacitance in
400µs (VBATT = 15V). For slower turn-on times, simply
add a small capacitor between the GATE and SRC
pins. When turned off, GATE and SRC pull low and typically discharge an 800pF gate capacitance in 80µs.
The MAX1614 provides separate on/off control inputs
(ON and OFF). ON and OFF connect, respectively, to
the SET and RESET inputs of an internal flip-flop. When
ON is pulsed low (with OFF = high), the internal charge
pump turns on, and GATE is pumped to 8V above SRC,
turning on the external MOSFETs. The charge pump
maintains gate drive to the external MOSFETs until OFF
is pulsed low. When this happens, the internal charge
pump turns off, and GATE discharges to ground
through an internal switch. For slower turn-on times,
simply add a small capacitor.
__________ Applications Information
Connecting ON/OFF to 3V or 5V Logic
ON and OFF internally connect to 2µA max pull-up
current sources (Figure 1). The open-circuit voltage
for ON and OFF ranges from 7V to 10.5V (nominally
8.5V). Since the current sources are relatively weak,
connecting ON and OFF directly to logic powered from
lower voltages (e.g., 3V or 5V) poses no problem if the
gate outputs driving these pins can sink at least 2µA
while high.
Although the MAX1614 shutdown function was designed
to operate with a single pushbutton on/off switch, it can
also be driven by a single gate. Connect ON to GND
and drive OFF directly (Figure 2).
Maximum Switching Rate
The MAX1614 is not intended for fast switching applications. In fact, it is specifically designed to limit the
rate of change of the load current, ∆I/∆t. The maximum
switching rate is limited by the turn-on time, which is a
function of the charge-pump output current and the
total capacitance on GATE (CGATE). Calculate the turnon time as a function of external MOSFET gate capacitance using the Gate Charging Current vs. VBATT graph
in the Typical Operating Characteristics. Since turn-off
time is small compared to turn-on time, the maximum
switching rate is approximately 1/tON.
Adding Gate Capacitance
The charge pump uses an internal monolithic transfer
capacitor to charge the external MOSFET gates.
Normally, the external MOSFET’s gate capacitance is
sufficient to serve as a reservoir capacitor. If the
MOSFETs are located at a significant distance from the
MAX1614, place a local bypass capacitor (100pF typ)
across the GATE and SRC pins. For slower turn-on
times, simply add a small capacitor between GATE and
SRC.
_______________________________________________________________________________________
5
MAX1614
______________________________________________________________Pin Description
MAX1614
High-Side, N-Channel MOSFET
Switch Driver
BATT
P
GATE
8.5V
LDO
CPUMP
POWER-ON
RESET (BATT < 2V)
1.21V
P
LBI
SRC
N
LBO
N
50kHz
OSC
SOFT
START
1µA
ON
1µA
N
OFF
ON
ON
OFF
STATE
0
0
OFF
0
1
ON
1
0
OFF
1
1
LAST VALID
STATE
MAX1614
GND
Figure 1. Functional Diagram
6
_______________________________________________________________________________________
High-Side, N-Channel MOSFET
Switch Driver
A simple undervoltage disconnect circuit is often desirable to prevent damage to secondary batteries due to
repeated deep discharge or cell reversal. The Typical
Operating Circuit turns off the MAX1614, disconnecting
the battery from the load when the battery voltage
falls below the minimum battery voltage required,
(VLOW BATT). VLOW BATT = (R1 + R2) / R2 x VTH where
VTH is the LBI input threshold (1.20V typ). When fresh
cells are installed or the batteries are recharged, a µC
or pushbutton reconnects the load.
MAX1614
SHUTDOWN
OFF
(CMOS OR TTL LOGIC)
ON
GND
Using LBO to Generate Early
Power-Fail Interrupt
Figure 2. Single-Line Shutdown Control
N
N
GATE
LOAD
SRC
Many applications require an early warning indicating
that power is failing so that the microprocessor (µP)
can take care of any “housekeeping” functions (storing
current settings in memory, etc.) before the power fails.
Connect LBI through a resistor divider across the battery, and connect LBO to the µP nonmaskable interrupt
(NMI). Set the threshold so that LBO goes low when the
battery decays to a point where regulation begins to
degrade (Figure 4). VLOW BATT = (R1 + R2) / R2 x VTH,
where VTH is the LBI input threshold (1.20V typ). Once
housekeeping is complete, the µP can turn off the load
by pulling OFF low.
ON
BATT
MAX1614
OFF
TO µC
R1
N
LBO
LBI
N
LOAD
R2
GND
GATE
SRC
ON
Figure 3. Single-Pushbutton On/Off Control
On/Off Control with a
Single Pushbutton Switch
The MAX1614’s separate on and off inputs allow maximum flexibility in controlling the external MOSFETs.
Connect a pushbutton switch to the ON pin and microcontroller (µC) I/O for single-button control. Connect the
OFF pin to another µC I/O pin. On the first button
depression, the MAX1614 turns on automatically; the
signal is also detected by the µC. When the button is
depressed a second time, the µC wraps around and
turns off the MAX1614 by pulling low on the OFF pin
(Figure 3).
BATT
MAX1614
TO µC
PORT PINS
OFF
R1
LBO
LBI
TO µC
NONMASKABLE
INTERRUPT
R2
GND
Figure 4. Using LBO to Generate Early Power-Fail Interrupt
_______________________________________________________________________________________
7
MAX1614
Simple Low-Battery Disconnect/Fresh
Battery Reconnect Circuit
MAX1614
High-Side, N-Channel MOSFET
Switch Driver
Increasing Low-Battery
Comparator Hysteresis
The MAX1614 contains an on-chip comparator with 2%
hysteresis for low-battery detection. If more than 2%
hysteresis is needed on the low-battery comparator and
LBO is connected to OFF, use the circuit in Figure 5 to
add hysteresis. The circuit of Figure 5 shows LBO controlling an N-channel MOSFET that shorts R2 to add
positive feedback to the trip point. This is necessary to
prevent loading down the 1µA pull-up at OFF (Figure 1).
LOAD
N
BATT GATE
SRC
ON
R1
MAX1614
N
OFF
R2
2N7002
(SOT23)
LBO
LBI
R3
___________________Chip Information
GND
TRANSISTOR COUNT: 264
R1 = 909kΩ
R2, R3 = 150kΩ
VL = 8.5V
VH = 9.8V
HYSTERESIS = 6%
SUBSTRATE CONNECTED TO GND
FALLING TRIP POINT VL
(
R1 + R3
VL = VTH
R3
)
RISING TRIP POINT VH
VH = VTH
(
R1 + R2 + R3
R3
)
Figure 5. Increasing Hysteresis of the Battery Disconnect
Circuit
________________________________________________________________Package Information
DIM
C
α
A
0.101mm
0.004 in
e
B
A1
L
A
A1
B
C
D
E
e
H
L
α
INCHES
MAX
MIN
0.044
0.036
0.008
0.004
0.014
0.010
0.007
0.005
0.120
0.116
0.120
0.116
0.0256
0.198
0.188
0.026
0.016
6°
0°
MILLIMETERS
MIN
MAX
0.91
1.11
0.10
0.20
0.25
0.36
0.13
0.18
2.95
3.05
2.95
3.05
0.65
4.78
5.03
0.41
0.66
0°
6°
21-0036D
E
H
8-PIN µMAX
MICROMAX SMALL-OUTLINE
PACKAGE
D
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.
8 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600
© 1996 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.