Datasheet

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LTC1255

Dual 24V High-Side

MOSFET Driver

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.

■

Fully Enhances N-Channel Power MOSFETs

■

12µA Standby Current

■

Operates at Supply Voltages from 9V to 24V

■

Short Circuit Protection

■

Easily Protected Against Supply Transients

■

Controlled Switching ON and OFF Times

■

No External Charge Pump Components

■

Compatible With Standard Logic Families

■

Available in 8-Pin SOIC

■

Solenoid Drivers

■

DC Motor Drivers

■

Stepper Motor Drivers

■

Lamp Drivers/Dimmers

■

Relay Drivers

■

Low Frequency H-Bridge

■

P-Channel Switch Replacement

ESCRIPTIO

ITY

12V

1N4001

10µF

IRLR024

24V

24V/0.5A

SOLENOID

DS2

LTC1255

IN2

GND

DS1

IN1

0.036Ω 0.036Ω

IRLR024

12V

1N4001

24V/0.5A

SOLENOID

FROM

µP, ETC.

FROM

µP, ETC.

LTC1255 • TA01

Standby Supply CurrentDual 24V High-Side Switch with Overcurrent Protection

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (µA)

15 20

LTC1255 • TA02

IN1

= V

IN2

= 0V

= 25°C

Summary of content (16 pages)

PAGE 1
LTC1255 Dual 24V High-Side MOSFET Driver U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ Fully Enhances N-Channel Power MOSFETs 12µA Standby Current Operates at Supply Voltages from 9V to 24V Short Circuit Protection Easily Protected Against Supply Transients Controlled Switching ON and OFF Times No External Charge Pump Components Compatible With Standard Logic Families Available in 8-Pin SOIC The LTC1255 dual high-side driver allows using low cost N-channel FETs for high-side industrial and automotive switchin
PAGE 2
LTC1255 W W W AXI U U ABSOLUTE RATI GS Supply Voltage ......................................... – 0.3V to 30V Transient Supply Voltage (< 10ms) ......................... 40V Input Voltage ..................... (VS + 0.3V) to (GND – 0.3V) Gate Voltage ...................... (VS + 20V) to (GND – 0.3V) Current (Any Pin)................................................. 50mA Operating Temperature Range LTC1255C............................................... 0°C to 70°C LTC1255I ...........................
PAGE 3
LTC1255 ELECTRICAL CHARACTERISTICS VS = 9V to 24V, TA = 25°C, unless otherwise noted.
PAGE 4
LTC1255 U W TYPICAL PERFOR A CE CHARACTERISTICS Input Threshold Voltage Drain Sense Threshold Voltage 2.4 2.0 1.8 1.6 VON 1.4 VOFF 1.2 1.0 0.8 0.6 0.4 0 5 15 20 10 SUPPLY VOLTAGE (V) 25 50 TA = 25°C 120 115 110 105 100 95 90 85 5 15 20 10 SUPPLY VOLTAGE (V) 30 0 500 400 VGS = 5V CGATE = 1000pF TIME FOR VGATE < 1V 0 30 25 20 15 35 30 25 20 15 10 5 5 0 0 0 5 15 20 10 SUPPLY VOLTAGE (V) LTC1255 • TA07 25 0 30 Supply Current per Channel (ON) 1.8 2.2 40 1.
PAGE 5
LTC1255 U U U 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.
PAGE 6
LTC1255 OPERATIO U Internal Voltage Regulation Drain Current Sense The output of the TTL-to-CMOS converter drives two regulated supplies which power the low voltage CMOS logic and analog blocks. The regulator outputs are isolated from each other so that the noise generated by the charge pump logic is not coupled into the 100mV reference or the analog comparator. The LTC1255 is configured to sense the current flowing into the drain of the power MOSFET in a high-side application.
PAGE 7
LTC1255 U U W U APPLICATIO S I FOR ATIO MOSFET AND LOAD PROTECTION The LTC1255 protects the power MOSFET switch by removing drive from the gate as soon as an overcurrent condition is detected. Resistive and inductive loads can be protected with no external time delay in series with the drain sense pin. Lamp loads, however, require that the overcurrent protection be delayed long enough to start the lamp but short enough to ensure the safety of the MOSFET. Large inductive loads (> 0.
PAGE 8
LTC1255 U U W U APPLICATIO S I FOR ATIO The RC network, RDELAY and CDELAY, in series with the drain sense input should be set to trip based on the expected characteristics of the load after startup, i.e., with this circuit, it is possible to power a large capacitive load and still react quickly to an overcurrent condition.
PAGE 9
LTC1255 U U W U APPLICATIO S I FOR ATIO 18V CDELAY 0.01µF RDELAY 100k VS + 100µF RSENSE 0.036Ω DS1 1N4148 1/2 LTC1255 IN1 IRF530 G1 GND 12V LOAD The large output capacitors on many switching regulators, on the other hand, may be able to hold the supply pin of the LTC1255 above 3.5V sufficiently long that this extra filtering is not required.
PAGE 10
LTC1255 U U W U APPLICATIO S I FOR ATIO The switches can either be turned OFF by the controlling logic during these transients or latched OFF above 30V by holding the drain sense pin low as shown in Figure 9. 14V + D1 MR2535L 1µF 50V VS Switch status can be ascertained by means of an XNOR gate connected to the input and switch output through 100k current limiting resistors (see Typical Applications section for more detail on this scheme).
PAGE 11
LTC1255 U TYPICAL APPLICATIO S 10 to 12 Cell Battery Switch and 5V Ramped Load Switch with 12µA Standby Current and Optional 3A Overcurrent Shutdown 18V TO 30V FROM BATTERY CHARGER 1N5400 9.1V MMBZ5239BL 10 TO 12 CELL BATTERY PACK 0.033Ω* IRFR024 IRFR024 SWITCHED BATTERY VIN 10k 0.22µF* 100k* + 12V MMBZ5242BL 2N2222 100µF 10k VS HIGH† EFFICIENCY SWITCHING REGULATOR VOUT 5V/1A + DS1 100µF G1 VLOGIC µP OR CONTROL LOGIC LTC1255 100k IN1 1N4148 DS2 IN2 GND 100k 1k MTD3055EL G2 0.
PAGE 12
LTC1255 U TYPICAL APPLICATIO S Low Frequency (fO = 100Hz) PWM Motor Speed Control with Current Limit and 22V Overvoltage Shutdown 14V OFF SLOW MED 1N4148 + MR2535L 0.1µF 50V 0.47µF 0.01Ω 60k 30k 10k VS 9.1k DS1 10k G1 + 5.6V 1µF FAST 10µF 50V 15k IN1 8 4 6 1k DS2 IN2 2 22V MMBZ5251BL LTC1255 GND 100k G2 IRFR024 22V MMBZ5251BL LMC555 5 3 100Ω 1N4148 0.01µF 1 0.
PAGE 13
LTC1255 U TYPICAL APPLICATIO S 18V to 32V Operation with Overcurrent Shutdown and Optional Overvoltage Shutdown 18V TO 32V 1k + 24V 1N5252B 1µF 50V 10k VS RSEN 0.10Ω 1W (IMAX = VBE/RSEN) 1k 2N3906 36V* 1N5258B DS1 2N3904 1/2 LTC1255 FROM µP, ETC.
PAGE 14
LTC1255 U TYPICAL APPLICATIO S H-Bridge DC Motor Driver (Direction and ON/OFF Control) 9V TO 24V + 10µF 50V 0.33µF VS DS1 100k G1 5V 1N4148 LTC1255 IN1 1/4 74C02 0.036Ω 100k IN2 1/4 74C02 DS2 GND 100k G2 MTD3055E MTD3055E 12V MMBZ5242B 1N4148 12V MMBZ5242B DC MOTOR 1/4 74C02 100k MTD3055EL 1N4148 LTC1255 • TA11 DIRECTION 100k DISABLE MTD3055EL 1N4148 High-Side DC Motor Driver With Electronic Braking and Stalled Motor Shutdown 18V + 100µF 0.
PAGE 15
LTC1255 U TYPICAL APPLICATIO S Stepper Motor Driver with Overcurrent Protection 12V + 0.036Ω 0.01µF VS 5V 0.036Ω DS1 IRFR024 12V MMBZ5242BL IN1 LTC1255 IRFR024 STEPPER MOTOR WINDINGS A C B C D IN2 GND G2 VS G1 12V MMBZ5242BL DS2 STEPPER MOTOR CONTROL LOGIC 0.
PAGE 16
LTC1255 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. N8 Package 8-Lead Plastic DIP 0.400 (10.160) MAX 8 7 6 5 0.250 ± 0.010 (6.350 ± 0.254) 1 0.300 – 0.320 (7.620 – 8.128) +0.635 –0.381 0.130 ± 0.005 (3.302 ± 0.127) 0.065 (1.651) TYP +0.025 0.325 –0.015 8.255 4 3 0.045 – 0.065 (1.143 – 1.651) 0.009 – 0.015 (0.229 – 0.381) ( 2 0.125 (3.175) MIN 0.045 ± 0.015 (1.143 ± 0.381) ) 0.018 ± 0.003 (0.457 ± 0.076) 0.100 ± 0.010 (2.540 ± 0.254) 0.020 (0.