2

dc1961af

DEMO MANUAL DC1961A

Quick start proceDure

Demonstration circuit 1961A is easy to set up to evalu-

ate the performance of the LT8309. Refer to Figure 1 for

proper measurement equipment setup and follow the

procedure below:

1. With power off, connect the input power supply to the

board through VIN and GND terminals. Connect the

load to the terminals VOUT+ and VOUT– on the board.

2. Turn on the power at the input.

NOTE: Make sure that the input voltage does not exceed

72V. To operate the board with higher input/output volt-

age, input capacitor, output capacitor and MOSFETs with

higher voltage ratings are needed.

3. Check for the proper output voltages. The output should

be regulated at 12V (±5%).

NOTE: The LT3748 requires a minimum load to maintain

good output voltage regulation. On the DC1961A, in order

to avoid pre-loading, a Zener diode is placed between its

VOUT+ and VOUT– to serve as a minimum load.

4. Once the proper output voltage is established, adjust

the input voltage and load current within the operating

range and observe the output voltage regulation, ripple

voltage, efficiency and other parameters.

NOTE:Whenmeasuringtheinputoroutputvoltageripples,

care must be taken to avoid a long ground lead on the

oscilloscope probe. Measure the input or output voltage

ripple by touching the probe tip directly across the VIN

and GND, or VOUT+ and VOUT– terminals. See Figure 2 for

proper scope probe technique.

Figure 2. Proper Scope Probe Placement for Measuring Input/Output Ripple

Figure 1. Proper Measurement Equipment Setup

INPUT OR OUTPUT CAPACITOR

+

–

IIN

VIN

POWER SUPPLY

– +

– +

+ –

IOUT

VOUT

–

+

–

+

LOAD