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19-1176; Rev 0; 12/96
High-Side, N-Channel MOSFET Switch Driver
_______________General Description
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. 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 6A while normal operation requires less than 25A. The MAX1614 is available in the space-saving MAX package that occupies about 60% less space than a standard 8-pin SO.
____________________________Features
o Internal On/Off Latch o High-Side, N-Channel Power MOSFET Drive o 25A (max) Quiescent Current o 6A (max) Off Current o Requires No External Components o 1.5%-Accurate Low-Battery Detector o Space-Saving MAX Package o 5V to 26V Input Voltage Range o Drives Single or Back-to-Back MOSFETs o Controlled Turn-On for Low Inrush Current
MAX1614
________________________Applications
Notebook Computers Portable Equipment Hand-Held Instruments Battery Packs
______________Ordering Information
PART MAX1614C/D TEMP. RANGE 0C to +70C PIN-PACKAGE Dice* 8 MAX
MAX1614EUA -40C to +85C *Contact factory for dice specifications.
__________Typical Operating Circuit
N N LOAD
__________________Pin Configuration
OPTIONAL FOR REVERSE CURRENT PROTECTION GATE SRC ON ON 1 BATT R1 LBI R2 GND LBO 8 BATT SRC GATE GND
TOP VIEW
MAX1614
OFF
OFF 2 LBO 3 LBI 4
MAX1614
7 6 5
MAX
________________________________________________________________ Maxim Integrated Products
1
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High-Side, N-Channel MOSFET Switch Driver MAX1614
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 = +70C) MAX (derate 4.10mV/C above +70C) .....................330mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +160C Lead Temperature (soldering, 10sec) .............................+300C
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 = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER BATT Operating Range BATT Shutdown Current ISHDN SYMBOL CONDITIONS VGATE - VSRC > 3V, SRC = BATT VBATT = 26V, ON = OFF = unconnected, IGATE = 0A, device latched off, VLBI = 1.5V VBATT = 15V, ON = OFF = unconnected, IGATE = 0A, device latched on, VLBI = 1.5V, SRC = BATT VBATT = 26V, ON = OFF = unconnected, IGATE = 0A, device latched on, VLBI = 1.5V, SRC = BATT MIN 5 4 TYP MAX 26 7 UNITS V A
17
30
A A
Quiescent Current
IBATT + ISRC
21
40
INTERNAL CHARGE PUMP Measured from GATE to SRC, VBATT = 15V, IGATE = 0A Measured from GATE to SRC, VBATT = VSRC = 5V, IGATE = 1.5A VGATE = VSRC = 15V VGATE = 4V, device latched off VTH LBI input falling Tested at VLBI = VBATT / 4 ILBI VOL VOH VLBI = 1.3V ISINK = 1mA VLBO = 11.5V Tested at 2V Tested at 0.6V VIL VIH tPW VBATT = 5V VBATT = 26V VBATT = 5V 2.0 0.5 1.0 0.5 1.5 2 0.6 6.5 3 15 0.5 1.182 1.20 0.02VTH 0.9 4 10 0.4 0.5 60 2 1.218 A mA V V V nA V A A A V V s 8 9.0 V
GATE Drive Voltage
VGS
GATE Drive Output Current GATE Discharge Current LOW-BATTERY COMPARATOR LBI Trip Level LBI Trip Hysteresis Minimum VBATT for Valid LBO LBI Input Current LBO Low Voltage LBO High Leakage CONTROL INPUTS (ON, OFF) Minimum Input Pull-Up Current Maximum Input Pull-Up Current Input Low Voltage Input High Voltage Minimum Input Pulse Width
2
_______________________________________________________________________________________
High-Side, N-Channel MOSFET Switch Driver
ELECTRICAL CHARACTERISTICS
(VBATT = 15V, TA = -40C to +85C, unless otherwise noted.) (Note 1) PARAMETER BATT Operating Range BATT Shutdown Current Quiescent Current INTERNAL CHARGE PUMP Measured from GATE to SRC, VBATT = 15V, IGATE = 0A Measured from GATE to SRC, VBATT = 5.25V, IGATE = 1.5A, VSRC = 5.25V VGATE = VSRC = 15V VTH LBI input falling 6.5 3 15 1.176 1.20 60 1.224 A V 9.0 V ISHDN IBATT + ISAC SYMBOL CONDITIONS VGATE - VSRC > 3V, SRC = BATT VBATT = 26V, ON = OFF = unconnected, IGATE = 0A, device latched off, VLBI = 1.5V VBATT = 26V, ON = OFF = unconnected, IGATE = 0A, device latched on, VLBI = 1.5V MIN 5.0 TYP MAX 26 8 40 UNITS V A A
MAX1614
GATE Drive Voltage
VGS
GATE Drive Output Current LOW-BATTERY LOW BATTERY COMPARATOR LBI Trip Level
Note 1: Specifications to -40C are guaranteed by design and not production tested.
__________________________________________Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
ON SUPPLY CURRENT vs. VBATT
MAX1614-01
OFF SUPPLY CURRENT vs. VBATT
TA = +85C TA = +25C TA = -40C 3.0 2.5 2.0 1.5 1.0
MAX1614-02
LOW-BATTERY THRESHOLD vs. TEMPERATURE
VBATT = 15V 1.28 LBI THRESHOLD (V) 1.26 1.24 1.22 1.20 1.18 1.16 VLBI FALLING
MAX1614-05
22 20 SUPPLY CURRENT (A) 18 16 14 12 10 8 6 5 10 15 20 25 TA = +25C TA = -40C TA = +85C
4.0 3.5 SHUTDOWN CURRENT (A)
1.30
VLBI RISING
30
5
10
15
20
25
30
-40
-20
0
20
40
60
80
100
VBATT (V)
VBATT (V)
TEMPERATURE (C)
_______________________________________________________________________________________
3
High-Side, N-Channel MOSFET Switch Driver MAX1614
____________________________Typical Operating Characteristics (continued)
(TA = +25C, unless otherwise noted.)
GATE-DISCHARGE CURRENT vs. GATE VOLTAGE
MAX1614-04
GATE-CHARGING CURRENT vs. TEMPERATURE
MAX1614--03
GATE-CHARGING CURRENT vs. BATT VOLTAGE
29 28 27 TA = -40C 26 25 24 23
MAX1614-06
2.5 TA = -40C GATE-DISCHARGE CURRENT (mA) 2.0 TA = +25C 1.5 1.0 0.5 0 -0.5 0 2 4 6 8 TA = +85C
34 GATE-CHARGING CURRENT (A) 33 32 31 30 29 28 27 26 -40 -20 0 20 40 60 80 VBATT = 15V
30 GATE-CHARGING CURRENT (A) TA = +85C
10 12 14 16 18 20
100
22 5 10 15 20 25 30 VBATT (V)
VGATE (V)
TEMPERATURE (C)
GATE AND SOURCE TRANSITIONS FOR TYPICAL MOSFET LOAD
MAX1614-07
GATE TURN-ON TRANSITION FOR TYPICAL MOSFET LOAD
Si9936 MOSFETS ILOAD = 1A ON = GND VGATE VSRC
MAX1614-08
VGATE VSRC
Si9936 MOSFETS ILOAD = 1A Ciss = 400pF ON = GND
5V/div
5V/div 0V VOFF 0V
VOFF
1ms/div
100s/div
GATE TURN-OFF TRANSITION FOR TYPICAL MOSFET LOAD
MAX1614-09
VGATE
Si9936 MOSFETS ILOAD = 1A Ciss = 400pF ON = GND
VSRC 5V/div
VOFF
20s/div
4
_______________________________________________________________________________________
High-Side, N-Channel MOSFET Switch Driver MAX1614
______________________________________________________________Pin Description
PIN 1 2 3 4 5 6 7 8 NAME ON OFF LBO LBI GND GATE SRC BATT FUNCTION 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. 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. Open-Drain, Low-Battery Comparator Output. LBO is low when VLBI is below the trip point. 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). System Ground Gate-Drive Output. Connect to the gates of external, N-channel MOSFETs. When the MAX1614 is off, GATE actively pulls to GND. Source Input. Connect to the sources of external, N-channel MOSFETs. When the MAX1614 is off, SRC actively pulls to GND. 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 30A, charging 800pF of gate capacitance in 400s (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 80s. 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.
lower voltages (e.g., 3V or 5V) poses no problem if the gate outputs driving these pins can sink at least 2A 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, t. The maximum I/ 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.
__________ Applications Information
Connecting ON/OFF to 3V or 5V Logic
ON and OFF internally connect to 2A 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
_______________________________________________________________________________________
5
High-Side, N-Channel MOSFET Switch Driver MAX1614
BATT
P 8.5V LDO POWER-ON RESET (BATT < 2V) 1.21V CPUMP
GATE
P
SRC
LBI
N
LBO
N
50kHz OSC SOFT START ON
1A OFF
1A N
ON 0 ON 0 1 1
OFF 0 1 0 1
STATE OFF ON OFF LAST VALID STATE
MAX1614
GND
Figure 1. Functional Diagram
6 _______________________________________________________________________________________
High-Side, N-Channel MOSFET Switch Driver
Simple Low-Battery Disconnect/Fresh Battery Reconnect Circuit
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 C or pushbutton reconnects the load.
MAX1614
SHUTDOWN (CMOS OR TTL LOGIC) OFF
MAX1614
GND
ON
Using LBO to Generate Early Power-Fail Interrupt
Figure 2. Single-Line Shutdown Control
N
N
LOAD
GATE
SRC ON
Many applications require an early warning indicating that power is failing so that the microprocessor (P) 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 P 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 P can turn off the load by pulling OFF low.
BATT R1 LBI R2
MAX1614
OFF
TO C
LBO
N
N
LOAD
GND GATE SRC ON BATT R1 LBI R2 GND LBO TO C NONMASKABLE INTERRUPT
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 (C) I/O for single-button control. Connect the OFF pin to another C I/O pin. On the first button depression, the MAX1614 turns on automatically; the signal is also detected by the C. When the button is depressed a second time, the C wraps around and turns off the MAX1614 by pulling low on the OFF pin (Figure 3).
MAX1614
TO C PORT PINS OFF
Figure 4. Using LBO to Generate Early Power-Fail Interrupt
7
_______________________________________________________________________________________
High-Side, N-Channel MOSFET Switch Driver MAX1614
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 1A pull-up at OFF (Figure 1).
N 2N7002 (SOT23) N LOAD
BATT GATE R1
SRC ON
MAX1614
R2 LBI R3 GND
OFF
LBO
___________________Chip Information
TRANSISTOR COUNT: 264 SUBSTRATE CONNECTED TO GND
R1 = 909k R2, R3 = 150k VL = 8.5V VH = 9.8V HYSTERESIS = 6%
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 A 0.101mm 0.004 in B A1 L
e
A A1 B C D E e H L
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 MAX 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 (c) 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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