Figure 2: Split Supply and Enable/Disable Configuration
ON = VDD
OFF = 0V
Enable Signal
Regulated Voltage = VDD
CDD
Battery Voltage = VIN
CIN
RSW
1 VDD
VA 8
2 RSW-Osc VB 7
3 REL-Osc CS 6
REL
4 GND
LX 5
HV857LMG
D
LX
CS
EL Lamp
HV857L
Audible Noise Reduction
The EL lamp, when lit, emits an audible noise. This is due to EL lamp construction and it creates a major problem for appli-
cations where the EL lamp can be close to the ear such as cellular phones. The HV857L employs a circuit designed to help
minimize the EL lamp’s audible noise by slowing down the rise and fall times seen by the EL lamp.
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