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PDF LTC1255C Data sheet ( Hoja de datos )
| Número de pieza | LTC1255C | |
| Descripción | Dual 24V High-Side MOSFET Driver | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
s Fully Enhances N-Channel Power MOSFETs
s 12µA Standby Current
s Operates at Supply Voltages from 9V to 24V
s Short Circuit Protection
s Easily Protected Against Supply Transients
s Controlled Switching ON and OFF Times
s No External Charge Pump Components
s Compatible With Standard Logic Families
s Available in 8-Pin SOIC
APPLICATI S
s Solenoid Drivers
s DC Motor Drivers
s Stepper Motor Drivers
s Lamp Drivers/Dimmers
s Relay Drivers
s Low Frequency H-Bridge
s P-Channel Switch Replacement
LTC1255
Dual 24V High-Side
MOSFET Driver
DESCRIPTIO
The LTC1255 dual high-side driver allows using low
cost N-channel FETs for high-side industrial and auto-
motive switching applications. An internal charge pump
boosts the gate drive voltage above the positive rail,
fully enhancing an N-channel MOS switch with no
external components. Low power operation, with 12µA
standby current, allows use in virtually all systems with
maximum efficiency.
Included on-chip is independent overcurrent sensing
to provide automatic shutdown in case of short circuits.
A time delay can be added to the current sense to
prevent false triggering on high in-rush current loads.
The LTC1255 operates from 9V to 24V supplies and is
well suited for industrial and automotive applications.
The LTC1255 is available in both an 8-pin DIP and an
8-pin SOIC.
TYPICAL APPLICATI
Dual 24V High-Side Switch with Overcurrent Protection
24V
0.036Ω
IRLR024
+
10µF
12V
VS
DS1 DS2
G1 LTC1255 G2
IN1 IN2
GND
0.036Ω
IRLR024
12V
24V/0.5A
SOLENOID
FROM
1N4001 µP, ETC.
FROM
µP, ETC.
1N4001
24V/0.5A
SOLENOID
LTC1255 • TA01
Standby Supply Current
50
45
VIN1 = VIN2 = 0V
TA = 25°C
40
35
30
25
20
15
10
5
0
0
5 10 15 20 25
SUPPLY VOLTAGE (V)
30
LTC1255 • TA02
1
1 page  
LTC1255
PI FU CTIO S
Input Pin
The LTC1255 input pin is active high and activates all of
the protection and charge pump circuitry when switched
ON. The LTC1255 logic and shutdown inputs are high
impedance CMOS gates with ESD protection diodes to
ground and supply and therefore should not be forced
beyond the power supply rails. The input pin should be
held low during the application of power to properly set
the input latch.
Gate Drive Pin
The gate drive pin is either driven to ground when the
switch is turned OFF or driven above the supply rail
when the switch is turned ON. This pin is of relatively
high impedance when driven above the rail (the equiva-
lent of a few hundred kΩ). Care should be taken to
minimize any loading of this pin by parasitic resistance
to ground or supply.
Supply Pin
The supply pin of the LTC1255 serves two vital pur-
poses. The first is obvious; it powers the input, gate
drive, regulation and protection circuitry. The second
purpose is less obvious; it provides a Kelvin connection
to the top of the drain sense resistor for the internal
100mV reference.
The supply pin of the LTC1255 should never be forced
below ground as this may result in permanent damage
to the device. A 100Ω resistor should be inserted in
series with the ground pin if negative supply voltage
transients are anticipated.
The LTC1255 is designed to be continuously powered
so that the gate of the MOSFET is actively driven at all
times. If it is necessary to remove power from the
supply pin and then reapply it, the input pin should be
cycled (low to high) a few milliseconds after the power
is reapplied to reset the input latch and protection
circuitry. Also, the input pin should be isolated from the
controlling logic by a 10k resistor if there is a possibility
that the input pin will be held high after the supply has
been removed.
Drain Sense Pin
The drain sense pin is compared against the supply pin
voltage. If the voltage at this pin is more than 100mV
below the supply pin, the input latch will be reset and
the MOSFET gate will be quickly discharged. Cycle the
input to reset the short-circuit latch and turn the MOSFET
back on.
This pin is also a high impedance CMOS gate with ESD
protection and therefore should not be forced outside
of the power supply rails. To defeat the overcurrent
protection, short the drain sense pin to the supply pin.
Some loads, such as large supply capacitors, lamps or
motors require high in-rush currents. An RC time delay
can be added between the sense resistor and the drain
sense pin to ensure that the drain sense circuitry does
not false trigger during startup. This time constant can
be set from a few microseconds to many seconds.
However, very long delays may put the MOSFET at risk
of being destroyed by a short-circuit condition (see
Applications Information section).
U
OPERATIO
The LTC1255 is a dual 24V MOSFET driver with built-in
protection and gate charge pump. The LTC1255 consists
of the following functional blocks:
TTL and CMOS Compatible Inputs and Latches
The LTC1255 inputs have been designed to accommo-
date a wide range of logic families. Both input thresh-
olds are set at about 1.3V with approximately 100mV of
hysteresis. A low standby current regulator provides
continuous bias for the TTL-to-CMOS converter.
The input/protection latch should be set after initial
power-up, or after reapplication of power, by cycling
the input low to high.
5
5 Page 
U
TYPICAL APPLICATIO S
10 to 12 Cell Battery Switch and 5V Ramped Load Switch with
12µA Standby Current and Optional 3A Overcurrent Shutdown
LTC1255
18V TO 30V
FROM
BATTERY
CHARGER
10 TO 12
CELL
BATTERY
PACK
9.1V
MMBZ5239BL
10k
2N2222
10k
VLOGIC
µP OR
CONTROL
LOGIC
100k
1N5400
0.033Ω*
IRFR024
IRFR024
0.22µF* 100k*
12V
MMBZ5242BL
+
VS DS1
G1
LTC1255
IN1 DS2
IN2 GND G2
1N4148
100k
*OPTIONAL 3A OVERCURRENT SHUTDOWN
†SEE LTC1149 DATA SHEET FOR CIRCUIT DETAILS
100µF
VIN
HIGH†
EFFICIENCY
SWITCHING
REGULATOR
VOUT
+
SWITCHED
BATTERY
5V/1A
100µF
1k
0.1µF
MTD3055EL
LTC1255 • TA04
5V/1A
(SWITCHED)
Automotive Motor Direction and Speed Control with
Stall-Current Shutdown
14V
+
MR2535L
10µF
50V
5V
DIRECTION
MOTOR SPEED
AND DIRECTION
CONTROL LOGIC
OR µP
DIRECTION
PWM 1
PWM 2
0.1µF
VS DS1
G1
LTC1255
IN1 DS2
IN2 GND G2
100Ω
0.1µF
100k
30k
0.02Ω
30k
MTD3055E
12V
MMBZ5242B
MTD3055E
12V
MMBZ5242B
14V
DC MOTOR
MTD3055EL
MTD3055EL
LTC1255 • TA05
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC1255C.PDF ] | |
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