QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 797
1MHZ SYNCHRONOUS BUCK-BOOST IN 3MM X 3MM DFN
LTC3440EDD
DESCRIPTION
Demonstration Circuit 797 is a constant-frequency
synchronous Buck-Boost converter using the
LTC3440EDD. The input range is from 2.5V to 5.5V,
making it ideal for single-cell Lithium-Ion or three-cell
NiCd/NiMH battery applications. This converter pro-
vides up to 95% efficiency, much higher than tradi-
tional Buck-Boost converters. For 2.5V minimum in-
put voltage, this converter can provide up to 540mA
load current.
The output voltage is set at 3.3V. A different output
voltage in the range of 2.5V 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 between efficiency and size. The frequency
can be modified by changing R6 or by synchronizing
to an external clock. In shutdown, the IC itself draws
less than 1µA.
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 DC797 to damp the possible voltage
transients. C8 is not needed for any application when
the 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.
LTC is a trademark of Linear Technology Corporation
Table 1. Performance Summary (T
A
= -40°C to 85°C unless otherwise noted)
°
°
PARAMETER
Minimum Input Voltage
Maximum Input Voltage
Output Voltage V
OUT
Maximum Output Current
Maximum Output Current
Typical Output Ripple V
OUT
Typical Switching Frequency
Efficiency (Fixed Freq.)
V
IN
= 4.2V, I
OUT
= 100mA
V
IN
= 4.2V, I
OUT
= 500mA
Off
On
V
IN
= 2.5V to 5.5V, I
OUT
= 0mA to 540mA
V
IN
= 2.5V
V
IN
= 2.7V
V
IN
= 2.5V, I
OUT
= 500mA (20MHz BW)
CONDITION
VALUE
2.5V
5.5V
3.3V ±4%
540mA
600mA
12mV
PP
(measured at C2)
22mV
PP
(measured across E4
and E5)
1MHz
94% Typical
91% Typical
0.4V MAX
1.5V MIN
On/Off Control
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 797
1MHZ SYNCHRONOUS BUCK-BOOST CONVERTER IN 3MM X 3MM DFN
QUICK START PROCEDURE
Demonstration circuit 797 is easy to set up to evalu-
ate the performance of the LTC3440EDD . Refer to
Figure 1 for proper measurement equipment setup
and follow the procedure below:
NOTE:
When measuring the input or output voltage
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-
ripple, care must be taken to avoid a long ground lead
on the oscilloscope probe. Measure the input or out-
put voltage ripple by touching the probe tip directly
across the Vin or Vout and GND terminals. See
Figure 2 for proper scope probe technique.
1.
Place jumpers in the following positions:
ceed 5.5V.
4.
Check for the proper output voltage. Vout = 3.17V
to 3.43V.
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, ad-
JP1
JP2
RUN
FIXED FREQ.
just the load within the operating range and ob-
serve the output voltage regulation, ripple voltage,
efficiency and other parameters.
2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 797
1MHZ SYNCHRONOUS BUCK-BOOST CONVERTER IN 3MM X 3MM DFN
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Ripple
VIN
GND
3
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 797
1MHZ SYNCHRONOUS BUCK-BOOST CONVERTER IN 3MM X 3MM DFN
Efficiency vs. Load
100%
90%
80%
70%
Efficiency%
60%
50%
40%
30%
20%
10%
0%
0.1
1
10
Iout (mA)
100
1000
2.7Vin PWM
3.6Vin PWM
4.2Vin PWM
2.7Vin Burst
3.6Vin Burst
4.2Vin Burst
Figure 3. Efficiency of DC797
Figure 4. Load Transient Response (Vin=3.6V; Channel 1: Vout, 100mV/div; Channel 2: Iout load step: 100mA to 500mA)
4
5
4
3
2
1
*
D
D3 IS RECOMMENDED FOR VIN>4.5V.
PLEASE REFER TO DATASHEET FOR DETAILS.
SUMIDA
CDRH4D28C/100
L1
10UH
1
2
1
2
D1
PMEG2010EA
PHILIPS
2
1
D3
POWERMITE
ON SEMI
OPT
SHDN
U1
LTC3440EDD
3
7
8
2
1
SW1
VIN
SHDN/SS
SW2
4
D
D2
PMEG2010EA
2
1
PHILIPS
C3
180PF
R1
340K
1%
R3
15K
C4
560PF
C5
10PF
R5
2.2K
C2
22UF,6.3V
1210
VOUT
C7
1UF
6.3V
0603
E4 VOUT
3.3V
VIN E1
2.5V-5.5V
VIN
+
C8
*
E5
GND
47UF,10V
TAJB
C
GND
C1
10UF
6.3V
1206
R4
1M
MODE/SYNC VC 10
RT
GND 5
11
VOUT 6
FB 9
C
R7
4.87M
R8
6.19M
C6
0.047UF
GND
SYNC
E2
E3
R6
60.4K
1%
R2
200K
1%
SYNC
VIN
BURST
MODE
1
FIXED
FREQ.
3
B
SHDN
1
2
RUN
3
JP1
2
B
JP2
VIN
2.5V
2.7V
IOUT
540mA
600mA
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A
CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS;
HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO
VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL
APPLICATION. COMPONENT SUBSTITUTION AND PRINTED
CIRUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT
PERFORMANCE OR RELIABILITY. CONTACT LINEAR
TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE.
THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
CONTRACT NO.
APPROVALS
DRAWN:
CHECKED: KIM T.
APPROVED:
NOTES: UNLESS OTHERWISE SPECIFIED
A
TECHNOLOGY
TITLE:
1630 McCarthy Blvd.
Milpitas, CA 95035
Phone: (408)432-1900
Fax: (408)434-0507
LTC Confidential-For Customer Use Only
A
1. ALL RESISTORS ARE IN OHMS, 0402.
ALL CAPS. ARE 0402.
2. INSTALL SHUNTS ON JP1 AND JP2 PIN 2 AND 3.
ENGINEER:
DONGYAN Z.
SIZE
DESIGNER:
1MHz SYNCHRONOUS BUCK-BOOST IN 3mm X 3mm DFN
A
DWG NO.
DATE: Friday, August 20, 2004
2
DC797A-1*LTC3440EDD
SHEET
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