Linear Technology 968A-B Quick Start Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 968A-B
DESCRIPTION
Demonstration circuit 968A-B is isolated input to high
current output 1/8th Brick footprint converter featur-
ing the LT ® 1952 switching controller. The DC968
converts isolated 18V to 36V input to 5V output and
provides over 20A of output current. The converter
operates at 300kHz with efficiency greater than 93%.
The DC968 can be easily modified to generate output
voltages in the range from 0.6V to 28V. The output
currents are limited by total output power of up to
200W. The other available versions of DC968A are:
DC968A-A 36-75Vin to 3.3V@30A
DC968A-C 36-75Vin to 12V@12A
DC968A-D 36-75Vin to 28V@4A
Also, the DC968 can be modified for other input volt-
ages like 8V-36V, 18V-75V, 44V-52V, and so on. The
wider input voltage range will decrease the converter
Performance Summary
Table 1.
PARAMETER
Minimum Input Voltage
Maximum Input Voltage
V OUT
Typical Output Ripple V OUT
Nominal Switching Frequency
QUICK START PROCEDURE
Demonstration circuit 968 is easy to set up to evalu-
ate the performance of LT1952 circuit. Refer to Fig-
ure 1 for proper measurement equipment setup and
follow the procedure below:
NOTE: When measuring the input or output voltage
ripple, care must be taken to avoid a long ground lead
on the oscilloscope probe. Measure the input or out-
put voltage ripple by touching the probe tip directly
ISOLATED DC/DC POWER CONVERTER
efficiency. Therefore, narrow input voltage range will
be more desirable.
The DC968 circuit features soft-start which prevents
output voltage overshoot on startup or when recover-
ing from overload condition.
The DC968 has precise over-current protection circuit
that allows for continuous operation under short cir-
cuit conditions. The low power dissipation under
short circuit conditions insures high reliability even
during short circuits.
The LT1952 can be synchronized to an external clock
of up to 400kHz. Please refer to LT1952 data sheet for
design details and applications information.
Design files for this circuit board are available. Call
the LTC factory.
LT is a trademark of Linear Technology Corporation
CONDITION
I OUT = 0A to 20A
I OUT = 0A to 20A
V IN = 18V to 36V, I OUT = 0A to 20A
V IN = 18V to 36V, I OUT = 0A to 20A
across the Vin or Vout and GND terminals. See Figure
2. for proper scope probe technique.
With power off, connect the input power supply to
1.
Vin and GND. Make sure that the input power sup-
ply has sufficient current rating at minimum input
voltage for the required output load.
Turn on the power at the input.
2.
LT1952
VALUE
18V
36V
5V ±3%
50mV P–P
300kHz
1