Typical Performance Characteristics
Current Limit Sense Voltage
Drift with Temperature
(Continued)
Current Limit Response Time
for Various Over Drives
Current Limit Sense Voltage
vs Supply Voltage
DS008711-38
DS008711-39
DS008711-40
Supply Current
Supply Current
Collector Current with
Emitter Output Below Ground
DS008711-41
DS008711-42
DS008711-43
Test Circuit
*
Parameter tests can be made using the test circuit shown.
Select the desired V
in
, collector voltage and duty cycle with
adjustable power supplies. A digital volt meter with an input
resistance greater than 100 MΩ should be used to measure
the following:
Input Reference Voltage to Ground; S1 in either position.
Level Shift Accuracy (%) = (T
P3
(V)/1V) x 100%; S1 at I
1
= I
2
= 1 mA
Input Current (mA) = (1V − T
p3
(V))/1 MΩ: S1 at I
1
= I
2
=
0 mA.
Oscillator parameters can be measured at T
p4
using a fre-
quency counter or an oscilloscope.
The Current Limit Sense Voltage is measured by connecting
an adjustable 0-to-1V floating power supply in series with the
current limit terminal and referring it to either the ground or
the V
in
terminal. Set the duty cycle to 90% and monitor test
point T
P5
while adjusting the floating power supply voltage
until the LM1578A’s duty cycle just reaches 0%. This voltage
is the Current Limit Sense Voltage.
The Supply Current should be measured with the duty cycle
at 0% and S1 in the I
1
= I
2
= 0 mA position.
*
LM1578A specifications are measured using automated
test equipment. This circuit is provided for the customer’s
convenience when checking parameters. Due to possible
variations in testing conditions, the measured values from
these testing procedures may not match those of the factory.
5
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