QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 625
1MHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER
1
LTC3441
DESCRIPTION
Demonstration Circuit 625 is a constant-frequency syn-
chronous Buck-Boost converter using the LTC3441. The
input range is from 2.4V to 5.5V, making it ideal for sin-
gle-cell lithium-ion or three-cell NiCd/NiMH battery ap-
plications. This converter provides up to 95% efficiency,
much higher than traditional Buck-Boost converters. For
2.5V minimum input voltage, this converter can provide
up to 1A load current.
The output voltage is set at 3.3V. A different output volt-
age in the range of 2.4V to 5.25V can be obtained by
changing one of the feedback resistors. The switching
frequency is set at 1MHz, which is a good trade-off be-
tween efficiency and size. Applying twice the desired
frequency at the MODE/SYNC pin can also synchronize
the switching frequency between 1.15MHz to 1.7MHz.
In shutdown, the IC draws less than 1
µ
A.
When using long wire connections to the input sources
(such as wall adaptors), there can be input over voltage
transients during initial plug-in. C8 is installed on
DC625 to damp the possible voltage transients. C8 is
not needed for any application when input source is
close to the regulator. Please refer to Application Note
88 for details.
Design files for this circuit board are available. Call
the LTC factory.
Table 1. Performance Summary (T
A
= 25°C unless otherwise noted)
PARAMETER CONDITION VALUE
Minimum Input Voltage -40
°
C to 85
°
C 2.4V (2.5V minimum input for 1A
load)
Maximum Input Voltage -40
°
C to 85
°
C 5.5V
Output Voltage V
OUT
V
IN
= 2.5V to 5.25V, I
OUT
= 0A to 1A 3.3V ±3%
Maximum Output Current V
IN
= 2.5V to 5.25V 1A
Typical Output Ripple V
OUT
V
IN
= 3.0V, I
OUT
= 1A (20MHz BW) 40mV
P–P
Typical Switching Frequency 1MHz
Efficiency V
IN
= 4.2V, I
OUT
= 0.2A
V
IN
= 4.2V, I
OUT
= 1A
94% Typical
89% Typical
Logic Low Voltage-Off, -40
°
C to 85
°
C 0.4V MAX
On/Off Control
Logic High Voltage-On 2.4V MIN
QUICK START PROCEDURE
Demonstration circuit 625 is easy to set up to evaluate
the performance of the LTC3441. Refer to Figure 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 output voltage
ripple by touching the probe tip directly across the Vin
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 625
1MHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER
2
or Vout and GND terminals. See Figure 2 for proper
scope probe technique.
1.
Place jumpers in the following positions:
JP1
RUN
FIXED FREQ.
2.
With power off, connect the input power supply to Vin
and GND.
3.
Turn on the power at the input.
NOTE:
Make sure that the input voltage does not ex-
ceed 5.5V.
4.
Check for the proper output voltage. Vout = 3.2V to
3.4V.
NOTE:
If there is no output, temporarily disconnect the
load to make sure that the load is not set too high.
5.
Once the proper output voltage is established, adjust
the load within the operating range and observe the
output voltage regulation, ripple voltage, efficiency
and other parameters.
Figure 1. Proper Measurement Equipment Setup
JP2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 625
1MHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER
3
Figure 2. Measuring Input or Output Ripple
GRAPHICS
Efficiency vs. Load
0.0%
10.0%
20.0%
30.0%
40.0%
50.0%
60.0%
70.0%
80.0%
90.0%
100.0%
0.1 1 10 100 1000
Iout (mA)
Efficiency%
2.7Vin PWM
3.6Vin PWM
4.2Vin PWM
2.7Vin Burst
3.6Vin Burst
4.2Vin Burst
Figure 3. Efficiency of DC625
VIN
GND
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 625
1MHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER
4
Figure 4. Load Transient Response (Vin=3V;Channel 1: Vout; Channel 2: Iout: load step from 100mA to 1A)
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 625
1MHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER
5
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 625
1MHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER
6
5
5
4
4
3
3
2
2
1
1
D D
C C
B B
A A
4
9
5
8
10
12
11
263
7
1
SW1
PVIN
SW2
VOUT
VIN
FB
VC
GNDPGNDPGND
MODE/SYNC
SHDN/SS
Linear Technology Corporation
LTC3441EDE
Bill Of Material
Demo Bd. #625A
6/17/2005
Item Qty Reference Part Description Manufacture / Part #
1 1 C1 Cap., X5R 10uF 6.3V 20% Taiyo Yuden JMK212BJ106MG-T
2 1 C2 Cap., X5R 0.047uF 16V 5% AVX 0402YD473JAT
3 2 C3,C7 Cap., NPO 220pF 25V 10% AVX 04023A221KAT2A
4 0 C4 (Opt) Cap., NPO 10pF 25V 10% AVX 04023A100KAT2A
5 1 C5 Cap., X5R 47uF 6.3V 20% Taiyo Yuden JMK325BJ476MM-T
6 1 C6 Cap., X5R 1uF 6.3V 10% Taiyo Yuden JMK107BJ105KA-T
7 1 C8 Cap., Tant. 47uF 10V 20% AVX TAJB476M010
8 0 C9 (Opt) Cap., X7R 1000pF 25V 20% AVX 04023C102MAT2A
9 2 D2,D1 Schottky Diode, 1A / 20V PHILIPS PMEG2010EA
10 2 JP1,JP2 Headers, 3 Pins 2mm Ctrs. CommConn Con Inc. 2802S-03G2
11 2 XJP1,XJP2 Shunt, 2 Pins 2mm Ctrs. CommConn Con Inc. CCIJ2MM-138G
12 1 L1 Inductor, 3.3uH TOKO A916CY-3R3M
13 1 R1 Res., Chip 1.0M 1/16W 5% AAC CR05-105JM
14 1 R2 Res., Chip 15K 1/16W 5% AAC CR05-153JM
15 1 R3 Res., Chip 200K 0.06W 1% AAC CR05-2003FM
16 1 R4 Res., Chip 348K 1/16W 1% AAC CR05-3483FM
17 1 R5 Res., Chip 5.1M 1/16W 5% AAC CR05-515JM
18 1 R6 Res., Chip 2.2K 0.06W 5% AAC CR05-222JM
19 0 R7 (Opt) Res., Chip 2.0 0.06W 1% AAC CR05-2R00FM
20 5 TP1,TP2,TP3,TP4,TP5 Turret, Testpoint Mill Max 2501-2
21 1 U1 I.C., Buck Converter Linear Tech. Corp. LTC3441EDE
22 4 SCREW, #4-40, 1/4" ANY
23 4 STANDOFF, #4-40 1/4" MICRO PLASTICS 14HTSP101
24 1 PRINTED CIRCUIT BOARD FAB., DEMO CIRCUIT 625A
25 2 TOP STENCIL STENCIL DC625A
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