DC349B Quick Start Guide
DESCRIPTION
Demonstration Circuit DC349B demonstrates a synchronous step-up DC/DC converter using the
LTC1700 controller.
The LTC1700 is a current mode No R
SENSE
™ synchronous step-up controller with up to 95%
efficiency. Applications include 2.5V to 3.3V or 5V converters, 2.5V to 5V converters, single-
cell Li-Ion to 5V applications or two cell AA to 3.3V or 5V applications.
The LTC1700’s 550kHz operating frequency allows the use of small inductors and capacitors.
The device can also be synchronized to frequencies between 400kHz to 750kHz. Burst Mode™
operation is disabled when the device is synchronized or the SYNC/MODE pin is pulled low to
reduce noise.
To prevent inductor current runaway, the duty cycle is limited to 90%. Overvoltage protection
turns both external MOSFETs off when the output rises about 5% above the regulated value.
DC349B provides output voltages of 3.3V or 5V (jumper selectable).
QUICK START GUIDE
1. Proper setup is essential for accurate and meaningful evaluation of efficiency and
regulation. Figure 1 shows the appropriate arrangement of supply, load, ammeters and
voltmeters.
Figure 1. DC349B Test and Measurement Setup
2. Apply a voltage source to the input of the circuit between the VIN and GND terminals. The
circuit will operate from an input voltage as low as 1.8V. Do not apply more than 4V to the
input.
3. Select the appropriate position of jumper JP1 for the output voltage (open for 5V, closed for
3.3V).
4. Refer to Figure 4 in the data sheet to apply an appropriate load current between the VOUT
and GND terminals at start-up.
5. The RUN terminal can be left unconnected. To shut down the LTC1700, connect this
terminal to GND.
6. Connect the SYNC/MODE terminal to the VIN terminal to enable Burst Mode operation at
low load currents or connect it to GND or an external clock to defeat Burst Mode operation.
Do not attempt to synchronize to a clock below 400kHz or above 750kHz.
PERFORMANCE SUMMARY
PARAMETER
Maximum Load Current
(Min)
(Note 1)
CONDITION
V
IN
= 2.5V, V
OUT
= 3.3V
VALUE
1A
V
IN
= 2.5V, V
OUT
= 5.0V
0.7A
V
IN
= 3.3V, V
OUT
= 5.0V
1A
Note 1: This limit is based on the DC349B circuit. The LTC1700 can provide higher output currents.
PARTS LIST
Item
Qty
Reference
Passive Comp.
C1
C2
C3
C4
C6
C7
C8
C9
R1
R2
R3
R4
L1
Active comp.
Q1
Q2
Part Description
Manufacture / Part #
1
2
3
4
5
6
7
8
9
10
11
12
13
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
CAP, X5R, 22uF, 6.3V, 20%, 1210
CAP, TANT, 68uF, 6.3V, 10% , 1210
CAP, X5R,10uF, 6.3V, 20%, 1206
CAP, POSCAP, 330uF, 6.3V, 7343
CAP, X7R, 0.1uF, 16V, 10%, 0603
CAP, X7R, 220pF, 25V, 10%, 0603
CAP, X7R, 100pF, 25V, 10%, 0603
CAP, X5R, 4.7uF, 6.3V, 20%, 0805
RES., CHIP 392K 1/16W 1% 0603
RES., CHIP 316K 1/16W 1% 0603
RES., CHIP 2.2K 1/16W 5% 0603
RES., CHIP 100K 1/16W 1% 0603
INDUCTOR, 1.5UH
P-MOSFET, AO4419, SO-08
N-MOSFET, AO4202, SO-08
TAIYO YUDEN JMK325BJ226MM-T
AVX, TAJB686K006RNJ
TAIYO YUDEN JMK316BJ106ML-T
PANASONIC 6TPB330M
AVX 0603YC104KAT2A
AVX 06033C221KAT2A
AVX 06033C101KAT2A
TAIYO YUDEN JMK212BJ475MG-T
VISHAY CRCW0603392KFKEA
VISHAY CRCW0603316KFKEA
VISHAY CRCW06032K20JNEA
VISHAY CRCW0603100KFKEA
MURATA LQH66SN1R5M03
ALPHA&OMEGA, AO4419
ALPHA&OMEGA, AO4202
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