鈥?/div>
first enabled
V
IN
V
IN
Connect the supply voltage to these terminals. Supply
voltage may range from 10 volts to 90 volts.
A high source impedance may cause oscillations when the
input voltage is near the undervoltage trip point. A high
source impedance results in a large voltage drop when
loaded, causing undervoltage lockout to kick in,
disconnecting the load. With the load removed, input voltage
rises, causing undervoltage to release and reconnecting the
load. The cycle repeats, resulting in oscillations. Source
impedance must be less than the following to avoid
oscillations:
reason, DC load at start-up should be less than 900mA.
Note that DC start-up load limitation decreases with added
load capacitance.
Connecting additional load capacitance alters the inrush
current limit. See the HV302/312 data sheet for details.
PWRGD
Connect to the power supply鈥檚 ENABLE inputs. Depending
on the power supply, it may be necessary to level-translate
this signal via opto-isolator or discrete circuit. Refer to the
HV302/312 data sheet for a description of PWRGD and
related application circuits.
PWRGD is an open-drain output. During start-up and
whenever V
IN
is lower than the undervoltage trip point or
greater than the overvoltage trip point, PWRGD assumes a
high impedance state. Once V
IN
is within the proper range
and the load capacitance has fully charged, PWRGD is
pulled down to V
IN-
.
R
SOURCE
<
3V
I
LOAD
V
OUT
Connect the power supply or other load to these terminals.
V
OUT+
is connected to V
IN+
, it is V
OUT鈥?/div>
that is switched.
Application of a DC load during start-up extends the time
inrush limiting is active. If this time exceeds 100ms, the
HV312 shuts off, retrying as quickly as 12s later. For this
rev 2 12SEP02
1
1
2
