DC1235A - Demo Manual

QUICK START GUIDE FOR DC1235
LOW QUIESCENT CURRENT DUAL SYNCHRONOUS BUCK CONVERTER
LTC3826EG-1
DESCRIPTION
Demonstration circuit 1235 is a dual-output stepdown
power supply. The input voltage is from 4.5V to 32V. The
supply has two outputs: 3.3V/5AMAX and 8.5V/3.5AMAX.
When the input voltage is
close to the output voltage, the supply is in dropout
mode. The design features the LTC3826-1, the low quiescent current, 2-phase, dual-output synchronous buck
regulator.
Table 1. Performance Summary
PARAMETER
CONDITION
VALUE
Input Voltage Range
If the input voltage must exceed 32V, use higher voltage rating input capacitors. The IC
works up to 36V. Minimum of 9V input is needed for 8.5V output regulation at 3A load.
4.5V to 32V
Outputs
VOUT1 = 3.3V, 0A to 5A
3.3V ± 2%
VOUT2 = 8.5V, 0A to 3.5A, Vin>9V
8.5V ± 2%
Typical Output Ripple (VOUT1)
20MHz BW, 5A load, VIN = 32V, frequency = 390kHz
35mVP-P
Typical Output Ripple (VOUT2)
20MHz BW, 3.5A load, VIN = 32V, frequency = 390kHz
30mVP-P
Typical Operating Frequency
PLLLPF floating (position JP1 to 390Khz)
390kHz
Typical input [email protected] load
CH1 on, no load, CH2 off, frequency=390kHz, Vin=16V. Burst Mode
55 uA
Efficiency for Vout1
VIN=12V, Vout1=3.3V at 3.5A, Fs=390KHz
94%
Efficiency for Vout2
VIN=12V, Vout2=8.5V at 2.5A, Fs=390kHz
98%
- TEST PROCEDURE
Refer to Figure 1 for proper measurement equipment
setup and follow the procedure below:
1. Set the power supply jumper’s as shown on Table 2
below.
JP1
JP2
JP3
JP4
JP5
JP6
FREQ
PLL/MODE
RUN1
RUN2
TRACK1
TRACK2
390kHz
BURST
ON
ON
SS1
SS2
3.With the input voltage set at approximately 20 volts,
check that the input current is below 100uA (Typically
85uA).
4. Connect the desired loads to the 3.3V (5 amps)
and 8.5V (3.5 amps) terminals and their closest PGND
terminals on the board.
5. Measure the output voltages. They should be 3.3V
±0.066V and 8.5V ±0.17V at 0 amps and full load.
Table 2 Default Jumper setting
6.Input current with both outputs at full load should
be about 2.5A with 20 Vin.
2. Connect the input power supply to the VIN and GND
terminals on the right, center of the board.
7.Check the default jumper position after finishing the
test evaluation of the board.
NOTE:
Do not increase VIN over 32V.
The maximum load at 3.3V is 5A, and the
maximum at 8.5V is 3.5A.
NOTE:
1
QUICK START GUIDE FOR DC1235
LOW QUIESCENT CURRENT DUAL SYNCHRONOUS BUCK CONVERTER
Load
+
A
V
Power
supply
+
V
+
A
V
+
A
Load
Figure 1. Proper Measurement Equipment Setup
1
QUICK START GUIDE FOR DC1235
LOW QUIESCENT CURRENT DUAL SYNCHRONOUS BUCK CONVERTER
Figure 2. LTC3826 demo circuit DC1235 circuit schematic
2
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