LTC1531_15 Datasheet, PDF (1/16 Pages) Linear Technology – Self-Powered Isolated Comparator

OBSOLETE PRODUCT
DATA SHEET FOR REFERENCE ONLY
Consult www.linear.com for possible alternate source.
FEATURES
■ _{UL Recognized File E151738 to UL1577}
■ _{Self-Powered Across Isolation Barrier}
■ _{2500VRMS Isolation}
■ _{2.5V Isolated Reference, ILOAD = 5mAMAX}
■ _{Zero-Cross Output for Line Power}
■ _{Dual Differential Input Comparator}
■ _{High Input Impedance Comparator}
U
APPLICATIO S
■ _{Self-Powered Isolated Sensing}
■ _{Isolated Temperature Control}
■ _{Isolated Voltage Monitor}
■ _{Isolated Switch Control}
, LTC and LT are registered trademarks of Linear Technology Corporation.
LTC1531
Self-Powered Isolated
Comparator
DESCRIPTIO
The LTC^®1531 is an isolated self-powered dual differential
comparator. An internal capacitive isolation barrier pro-
vides 2500V_RMS of isolation between the comparator and
its output. The part provides UL-rated isolated compari-
sons without the need for an isolated supply since both
comparator power and output data are transmitted across
the capacitive barrier. The comparator data is transferred
differentially across the isolation barrier to provide high
common mode voltage and noise immunity.
The isolated side can supply a 2.5V reference output to
power external sensor circuits such as a thermistor bridge.
The dual differential comparator inputs allow for compari-
son of two differential voltages as well as single-ended
voltages. The powered side provides a latched data output
as well as a pulsed zero-cross comparator output for
controlling a triac. The part is available in a 28-lead SO
package.
TYPICAL APPLICATION
Isolated Thermistor Temperature Controller
AC
120V
TECCOR
Q4008L4
OR EQUIVALENT
NEUTRAL
LOAD
25Ω
150Ω
1k
2N2222
1N4004
3k
3W
750Ω
0.5W
DANGER!
LETHAL VOLTAGES
IN THIS SECTION!
+ _20μF
50V
–5.6V
R1
680k
+
100μF
5.6V
390Ω
LED
R2
C1
47k
0.01μF
V_CC
ZCDATA
SHDN
ZCPOS ZCNEG
DATA
QD
VALID
GND
LTC1531
ISOLATION
BARRIER
V_PW
2.5V ^VREG
V1
V2
+
V3
–
V4
CMPOUT
ISOGND
1μF
1
R_THERM =
R_{O • e}B (1/T – 1/T_O)
B = 3807
T_O = 297°K
THERM
T 30k
YSI 44008
R5*1M
R4
50k
R6
22k
1
1
1 ^{1531 TA01}
1 = ISOLATED GROUND
*HYSTERESIS = 1°C AT T_O
1