sc1437 Semtech Corporation, sc1437 Datasheet

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sc1437

Manufacturer Part Number
sc1437
Description
Precision Voltage Detector With Programmable Trigger Voltage & Timer Delay
Manufacturer
Semtech Corporation
Datasheet
The SC1437 is a battery over voltage detection circuit with driver
for external MOSFET. The trip point is adjustable with an external
resistor divider connected to the SENSE pin. The trip point is
preset to a nominal trip voltage of 4.2V if no external divider is
used. Other internal trip voltages of 4.5V and 4.7V are available,
specified by different part numbers. An internal delay, with two
selectable times or bypass, is on-board to suppress accidental
over voltage conditions due to glitches on the battery supply volt-
age, V+. The delay is externally adjustable by pulling the SEL pin
high, low, or left floating. During an actual over voltage condition,
the internal driver will pull the over voltage pin (OV) down to the
voltage present at the V- pin. This insures the external N-Channel
MOSFET will be completely off during an over voltage condition.
Supply current during the monitoring mode of operation is ap-
proximately 10µA. If an over voltage condition is detected, supply
currents increase when the timer is started. A voltage comparator
will engage at voltages greater than 6.8V, which bypasses the
timer and open circuits the battery by turning off the external
MOSFET. This important function protects the battery during the
timer delay in the event of a charger failure. There are three
functional options available. With the B option the OV pin is active
low. With the L option the OV pin is active high. With the H option
the OV pin is open drain, active high. All options are available in a
5 lead SOT-23 package.
POWER MANAGEMENT
Revision 01/10/2001
Description
Typical Application Circuit
BATTERY
R1
R2
Programmable Trigger Voltage & Timer Delay
0.1uF
100
1
 Low quiescent current, less than 10µA typical
 Input voltage range 1.8V to 6.8V
 Adjustable or preset voltage trip point
 Selectable timer delays of 0, 40 and 80ms without use of
 SOT-23 5 lead package
 Accuracy is 2% over specified temperature range
 30V maximum rating
 Battery packs
 Portable electronics
 Lithium Ion protection circuits
 Programmable Fuse
 Power Monitoring
 CPU Reset Circuits
Features
Applications
1
4
3
external resistor
Precision Voltage Detector With
SEL
SENSE
OV
SC1437
V+
V-
VTRIP = 2.1(1+
0.476 < (
5
2
R2
0.1uF
/
R1
) < 2
R2
/
R1
)
100
www.semtech.com
SC1437
+
-

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sc1437 Summary of contents

Page 1

... POWER MANAGEMENT Description The SC1437 is a battery over voltage detection circuit with driver for external MOSFET. The trip point is adjustable with an external resistor divider connected to the SENSE pin. The trip point is preset to a nominal trip voltage of 4. external divider is used. Other internal trip voltages of 4.5V and 4.7V are available, specified by different part numbers ...

Page 2

... www.semtech.com SC1437 ° ° C ° C ° C ° µ ...

Page 3

... POWER MANAGEMENT Pin Configuration Top View SEL SOT-23-5L Marking Information Top Mark 7B45 7 = SC1437 Device Output Option Output active low L = Output active high H = Output active high, with open drain Voltage Option 4.2V 4.5V 4.7V Pin Descriptions ...

Page 4

... POWER MANAGEMENT Block Diagram V+ SENSE * Based on version selected 4.2V, 4.5V, 4. option: Output active low L option: Output active high H option: Output active high, open drain 2000 Semtech Corp. V+ COMPARATOR 6.8V CLAMP MUX V+ DELAY TIMER SEL 4 SC1437 V+ 4.2V DRIVER OV V- www.semtech.com ...

Page 5

... JP2, JP3 or leaving the jumper off, respectively. Configuration of timing delays are shown in Table 1. Once the trip delay is set to the required value the SC1437 will monitor the charger voltage. If the charger voltage equals or exceeds 5.5V the OV pin will transition from high to low (Version B) turning Q1 off, thereby breaking the circuit and protecting the battery from overvoltage ...

Page 6

... SC1437 1 CHARGER+ R3 100 SEL SENSE SC1437 C1 0.1uF 1 rip delay Se rip dela rip dela Set 40mS, JP2 Shor o 40mS, JP2 Shor o 40mS, JP2 Short ed. o 40mS, JP2 Shor rip dela 40mS, JP2 Shor www ...

Page 7

... Against T Plo Plo ed A INTERNAL TRIP VOLTAGE DEVIATION OVER TEMPERATURE 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 -0.6 -40 - TEMPERATURE (Degrees C) 7 SC1437 rip V rip V oltage (4.7V) De oltage (4.7V) De viation viation rip V rip Voltage (4.7V) De oltage (4.7V) Deviation oltage (4.7V) De viation viation gainst T gainst T gainst T gainst Tem em emperature perature. perature. ...

Page 8

... POWER MANAGEMENT Outline Drawing - SOT23-5 Land Pattern - SOT23-5 Contact Information 2000 Semtech Corp. Semtech Corporation Power Management Products Division 652 Mitchell Rd., Newbury Park, CA 91320 Phone: (805)498-2111 FAX (805)498-3804 8 SC1437 www.semtech.com ...

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