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 evaluatio n 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 CONDITION VALUE
Maximum Load Current
(Min)
(Note 1)
VIN = 2.5V, VOUT = 3.3V
VIN = 2.5V, VOUT = 5.0V
VIN = 3.3V, VOUT = 5.0V
1A
0.7A
1A
Note 1: This limit is based on the DC349B circuit. The LTC1700 can provide higher output currents.
PARTS
LIST
Item Qty Reference Part Description Manufacture / Part #
Passive Comp.
1 1 C1 CAP, X5R, 22uF, 6.3V, 20%, 1210 TAIYO YUDEN JMK325BJ226MM-T
2 1 C2 CAP, TANT, 68uF, 6.3V, 10% , 1210 AVX, TAJB686K006RNJ
3 1 C3 CAP, X5R,10uF, 6.3V, 20%, 1206 TAIYO YUDEN JMK316BJ106ML-T
4 1 C4 CAP, POSCAP, 330uF, 6.3V, 7343 PANASONIC 6TPB330M
5 1 C6 CAP, X7R, 0.1uF, 16V, 10%, 0603 AVX 0603YC104KAT2A
6 1 C7 CAP, X7R, 220pF, 25V, 10%, 0603 AVX 06033C221KAT2A
7 1 C8 CAP, X7R, 100pF, 25V, 10%, 0603 AVX 06033C101KAT2A
8 1 C9 CAP, X5R, 4.7uF, 6.3V, 20%, 0805 TAIYO YUDEN JMK212BJ475MG-T
9 1 R1 RES., CHIP 392K 1/16W 1% 0603 VISHAY CRCW0603392KFKEA
10 1 R2 RES., CHIP 316K 1/16W 1% 0603 VISHAY CRCW0603316KFKEA
11 1 R3 RES., CHIP 2.2K 1/16W 5% 0603 VISHAY CRCW06032K20JNEA
12 1 R4 RES., CHIP 100K 1/16W 1% 0603 VISHAY CRCW0603100KFKEA
13 1 L1 INDUCTOR, 1.5UH MURATA LQH66SN1R5M 03
Active comp.
1 1 Q1 P-MOSFET, AO4419, SO-08 ALPHA&OMEGA, AO4419
2 1 Q2 N-MOSFET, AO4202, SO-08 ALPHA&OMEGA, AO4202
3 1 U1 I.C., LTC1700EMS MSOP10 LINEAR LTC1700EMS#PBF
Hardware
1 6 E1-E6 TURRET, MILL-MAX 2501-2
2 1 JP1 0.079 SINGLE ROW HEADER, 2 pin COMM CON 2802S-02 -G1
3 1 JP2 0.079 SINGLE ROW HEADER, 3 pin COMM CON 2802S-03 -G1
4 2 XJP1, XJP2 SHUNT, .079" CENTER SAMTEC, 2SN-BK-G
5 1 PRINTED CIRCUIT BOA RDS DEMO BOARD 349B
