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PDF LTC1155 Data sheet ( Hoja de datos )
| Número de pieza | LTC1155 | |
| Descripción | Dual High Side Micropower MOSFET Driver | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
s Fully Enhances N-Channel Power MOSFETs
s 8µA Standby Current
s 85µA ON Current
s Short-Circuit Protection
s Wide Power Supply Range: 4.5V to 18V
s Controlled Switching ON and OFF Times
s No External Charge Pump Components
s Replaces P-Channel High Side MOSFETs
s Compatible with Standard Logic Families
s Available in 8-Pin SO Package
APPLICATI S
s Laptop Power Bus Switching
s SCSI Termination Power Switching
s Cellular Phone Power Management
s P-Channel Switch Replacement
s Relay and Solenoid Drivers
s Low Frequency Half H-Bridge
s Motor Speed and Torque Control
LTC1155
Dual High Side
Micropower MOSFET Driver
DESCRIPTIO
The LTC®1155 dual high side gate driver allows using low
cost N-channel FETs for high side switching applications.
An internal charge pump boosts the gate above the posi-
tive rail, fully enhancing an N-channel MOSFET with no
external components. Micropower operation, with 8µA
standby current and 85µA operating current, allows use in
virtually all systems with maximum efficiency.
Included on-chip is overcurrent sensing to provide auto-
matic shutdown in case of short circuits. A time delay can
be added in series with the current sense to prevent false
triggering on high in-rush loads such as capacitors and
incandescent lamps.
The LTC1155 operates off of a 4.5V to 18V supply input
and safely drives the gates of virtually all FETs. The
LTC1155 is well suited for low voltage (battery-powered)
applications, particularly where micropower “sleep” op-
eration is required.
The LTC1155 is available in both 8-pin PDIP and 8-pin SO
packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATI
Laptop Computer Power Bus Switch with Short Circuit Protection
RSEN
0.02Ω
RDLY
100k
VS = 4.5V TO 5.5V
CDLY
0.1µF
+
10µF
DS1 VS DS2
CDLY
0.1µF
RDLY
100k
*IRLR034
5A
MAX
TTL, CMOS INPUT
G1 LTC1155 G2
IN1 GND IN2
*IRLR034
TTL, CMOS INPUT
RSEN
0.02Ω
5A
MAX
POWER BUS
µP
SYSTEM
DISK
DRIVE
GND
*SURFACE MOUNT
DISPLAY
PRINTER,
ETC.
1155 TA01
Switch Voltage Drop
0.25
0.20
0.15
0.10
0.05
0.00
0
12
OUTPUT CURRENT (A)
3
1155 TA02
1
1 page  
LTC1155
PIN FUNCTIONS
The supply pin of the LTC1155 should not be forced below
ground as this may result in permanent damage to the
device. A 300Ω resistor should be inserted in series with
the ground pin if negative supply voltages are anticipated.
Drain Sense Pin
As noted previously, 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 beyond the
power supply rails. To defeat the over current protection,
short the drain sense to supply.
Some loads, such as large supply capacitors, lamps or
motors require high inrush currents. An RC time delay
must be added between the sense resistor and the drain
sense pin to ensure that the drain sense circuitry does not
false trigger during start-up. This time constant can be set
from a few microseconds to many seconds. However, very
long delays may put the MOSFET in risk of being destroyed
by a short-circuit condition (see Applications Information
section).
BLOCK DIAGRA
VS
LOW STANDBY
CURRENT
REGULATOR
IN
TTL-TO-CMOS
CONVERTER
GND
ANALOG SECTION
100mV
REFERENCE
COMP
10µs
DELAY
ANALOG DIGITAL
VOLTAGE
REGULATORS
ONE
SHOT
R INPUT
S LATCH
DRAIN
SENSE
GATE CHARGE
AND DISCHARGE
CONTROL LOGIC
GATE
OSCILLATOR
AND CHARGE
PUMP
FAST/SLOW
GATE CHARGE
LOGIC
1155 BD
U
OPERATIO
The LTC1155 contains two independent power MOSFET
gate drivers and protection circuits (refer to the Block
Diagram for details). Each half of the LTC1155 consists of
the following functional blocks:
TTL and CMOS Compatible Inputs
Each driver input has been designed to accommodate a
wide range of logic families. The input threshold is set at
1.3V with approximately 100mV of hysteresis.
A voltage regulator with low standby current provides
continuous bias for the TTL to CMOS converters. The TTL
to CMOS converter output enables the rest of the circuitry.
In this way the power consumption is kept to a minimum
in the standby mode.
Internal Voltage Regulation
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.
5
5 Page 
LTC1155
TYPICAL APPLICATI S
Automotive High Side Driver with Reverse-Battery
and High Voltage Transient Protection
5V/3A Extremely Low Voltage Drop Regulator with 10µA Standby
Current and Short-Circuit Protection
9V TO 16V
+
10µF
5V
100k*
VS DS1
IN1
1/2
LTC1155
G1
GND
CDLY**
RDLY**
0.02Ω
5%
18V
1N4746A
18V
1N4746A
MTP50N05E
300Ω
1/4W
M
*PROTECTS TTL/CMOS GATES DURING HIGH VOLTAGE
TRANSIENT OR REVERSE BATTERY
**NOT REQUIRED FOR INDUCTIVE OR RESISTIVE LOADS
VALVE,
ETC.
1155 TA08
5.2V TO 6V
+
10µF
ON/OFF
VS DS1
IN1
1/2
LTC1155
G1
GND
FAULT
0.1µF
0.1µF
300k
0.02Ω
100k
200pF
IRLR024
10k
1
83
5V/3A
LT1431
74
+
65
470µF*
*CAPACITOR ESR SHOULD BE LESS THAN 0.5Ω
1155 TA09
Using the Second Channel for Fault Detection
4.5V TO 5.5V
FLT
µP OR
CONTROL
LOGIC
ON/OFF
+
100k 10µF
1N4148
1N4148
DS1
G2
100k
IN2
VS
LTC1155
0.1µF*
DS2
0.05Ω
30k*
SMD25N05-45L
IN1 GND
G1
LOAD
NOTE:
DRAIN SENSE 2 IS USED TO DETECT A FAULT IN CHANNEL 1.
GATE 2 PULLS DOWN ON DRAIN SENSE 1 TO DISCHARGE
THE MOSFET AND REPORT THE FAULT TO THE µP
*NOT REQUIRED FOR RESISTIVE OR INDUCTIVE LOADS
1155 TA10
Bootstrapped Gate Drive for (100Hz < FO < 10kHz)
9V TO 18V
5V
µP OR
CMOS/TTL
LOGIC
0.01µF
VS DS1
IN1
1/2
LTC1155
G1
GND
30k
2N2222
1N4148
0.01Ω
0.1µF
IRFZ44
VGATE = 2VS – 0.6V
18V
2N3906
LOAD
RISE AND FALL TIMES ARE βETA TIMES FASTER
1155 TA11
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC1155.PDF ] | |
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