DC989B-A - Demo Manual

QUICK START GUIDE FOR DC989B-A
TINY NO RSENSE BOOST CONVERTER
LTC3872
DESCRIPTION
Demonstration circuit 989B-A is a single-output
boost converter, it features tiny, boost controller
LTC3872. The input voltage is from 3.0V to 4.5V
without output de-rating. The supply has one output: 5V/2AMAX. Minimum input voltage is 2.75V.
When input voltage is lower than 3V, output current should be de-rated. The design employs the
LTC3872, the small footprint NO RSENSE boost
regulator. The switching frequency is fixed at 550
kHz. With current mode control and OPTI-LOOP
compensation, DC989B-A can be optimized to
provide fast transient response. NO RSENSE technique reduces both: size of the converter and
power dissipation. However, care should be taken
to MOSFET selection, it’s not only switching element, but also its RDS(ON) represents the current
sensing element for the control loop, see LTC3872
datasheet for details. LTC3872 allows design
small size and high efficiency step-up DC/DC solutions.
Design files for this circuit board are available.
Call the LTC factory.
TM-NO RSENSE is trademark of Linear Technology Corporation
Table 1. Performance Summary (TA = 25°C)
PARAMETER
CONDITION
VALUE
Minimum Input Voltage
If the input voltage must be lower than 3V, degrade output load current.
2.75V
Maximum Input Voltage
4.5V
Output Voltage VOUT
5V +/- 2%
Maximum Continuous output
Current
Vin = 3V to 4.5V
2A
Typical Operating Frequency
Fixed
550kHz
Typical Output Ripple (VOUT)
20MHz BW, 2A load, VIN = 3V, frequency = 550kHz
30mVP-P
Efficiency
VIN=3V, VOUT=5V IOUT=2A
90%
QUICK START PROCEDURE
Demonstration circuit 989B-A is easy to set up to
evaluate the performance of the LTC3872. Please
refer to Figure 1 for proper measurement equipment setup and follow the procedure below:
2. Connect the input power supply to the VIN
and GND terminals on the right, center of
the board.
NOTE: Do not increase VIN over 5V.
1. Place RUN in ON position for normal operation.
Connect the desired loads between 5V output
terminal and the GND terminal on the board.
3. Vary the input voltage from 3.0V to 4.5V
and adjust the load current from 0 to 2A.
Measure the output voltages. VOUT should
read between 5.0V 0.1V within specified
maximum load current.
4. Measure the output ripple voltage at maximum output current level and minimum in-
NOTE:
The maximum load is 2A.
1
QUICK START GUIDE FOR DC989B-A
TINY NO RSENSE BOOST CONVERTER
put voltage; it usually will measure less
than 30mV.
A
Figure 1. Proper Measurement Equipment Setup
Figure 2. Scope Probe Placements for Measuring Input or Output Ripple.
2
QUICK START GUIDE FOR DC989B-A
TINY NO RSENSE BOOST CONVERTER
Figure 3. Typical Switch Node and Output Ripple Waveform
VIN=3.0V, VOUT=5V, IOUT=2A
Vout
200mV/DiV
Iout
1A/DiV
Figure 4. Load Step Response
VIN = 3.3V, VOUT = 5V & 1.6A Load Step
2
3
OFF
J1
2
ON
1
RUN/SS
R6
OPT
VIN
RUN/SS
47pF
C7
C6
1800pF
R3
17.4K 1%
R5
OPT
C4
(opt)
R1
11K 1%
3
2
1
R4
5.11 K 1%
VFB
ITH
IPRG
U1
[1]
6
RUN
SW
5
C5
OPT
C9
0.1uF
RUN/SS
7
8
R2
34.8K 1%
NGATE
V IN
G ND
4
4
Q3
Si4116DY
OPT
Q1
Si3460DDV
3
2
L1
1.0uH
FDV0630-1R0
1
2
5
6
4
C10
10uF
10V
D1
B320
5
6
7
8
1
2
3
1
C1
100uF
10V
[1]
C2
100uF
10V
Vout
IC
LTC3872ETS8
LTC3872-1ETS8
-B
C13
OPT
-A
C3
OPT
+
VERSION
C11
OPT
C8
470uF
Sanyo TPE
For Demo Board
Test Only
Vin
E4
E3
E2
E1
GND
[email protected]
VOUT
GND
3V-4.5V
VIN
QUICK START GUIDE FOR DC989B-A
TINY NO RSENSE BOOST CONVERTER
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QUICK START GUIDE FOR DC989B-A
TINY NO RSENSE BOOST CONVERTER
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