10
LTC1255
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.
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). The switch is reset
after the overvoltage event by cycling the input low and
then high again.
The power MOSFET switch should be selected to have a
breakdown voltage sufficiently higher than the 40V supply
clamp voltage to ensure that no current is conducted to the
load during the transient.
APPLICATIO S I FOR ATIO
WUU U
Figure 9. Overvoltage Transient Protection
TYPICAL APPLICATIO S
U
Dual Automotive High-Side Switch with Overvoltage Protection,
XNOR Status and 12µA Standby Current
V
S
DS1
1/2 LTC1255
G1
GND
IN1
IRF530
12V
1N5242B
14V
R
SENSE
0.036Ω
LTC1255 • F09
LOAD
100Ω
10k
1k*
D1
MR2535L
30V*
1N5256B
FROM
µP, ETC.
+
1µF
50V
*OPTIONAL OVERVOLTAGE (30V) LATCH-OFF COMPONENTS
V
S
DS2
LTC1255
IN2
GND
DS1
IN1
G1
G2
MTD3055E
1N5400
14V
MR2535L*
0.036Ω
LTC1255 • TA03
10k**
12V
MMBZ5242B
100k
10k
FAULT
TO µP
FROM
µP, ETC.
100Ω
+
1µF
50V
FAULT
TO µP
FROM
µP, ETC.
10k
100k
1N5400
12V
MMBZ5242B
10k** MTD3055E
14V/1A
SOLENOID
0.036Ω
14V/1A
SOLENOID
1/4 74C266
†
LIMITS V
S
TRANSIENTS TO <40V. SEE MANUFACTURER DATA SHEET FOR
FURTHER DETAIL.
OPTIONAL OPEN LOAD DETECTION REQUIRES 10k PULL-UP RESISTORS.
(ULTRA LOW STANDBY QUIESCENT CURRENT IS SACRIFICED)
POWER FROM 5V LOGIC SUPPLY.
*
**
†
IN
0
1
0
1
OUT
0
0
1
1
CONDITION
SWITCH OFF
OVERCURRENT
OPEN LOAD**
SWITCH ON
FAULT
1
0
0
1
TRUTH TABLE
1/4 74C266
†
