QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 760
BOOST AND INVERTING DC/DC CONVERTERS
LT3472EDD
DESCRIPTION
Demonstration circuit 760 is a Dual, 1.1MHz
Boost/Inverter in 3mmx 3mm DFN featuring the
LT3472EDD. The demo circuit demonstrates small
size and low component count in a Boost Circuit and
an Inverting Circuit. The Boost Converter is designed
to convert a 2.7V-4.2V input to 15V output at 25mA-
45mA load. The Inverting Circuit generates a -8V out-
put at 35mA-65mA from the same input. Since the
maximum Vin of the LT3472DD is 16V, this demo cir-
cuit will work well at higher inputs. The only limitation
is the 10V rating of the input capacitor. The LT3472
features integrated Schottky diodes for both outputs
and requires only one resistor (per output) to set the
Table 1. Performance Summary (T
A
= 25°C)
PARAMETERS FOR 15V BOOST CIRCUIT
Minimum Input Voltage
Maximum Input Voltage
Output Voltage V
OUT
Output Voltage V
OUT
Maximum Output Current
Maximum Output Current
Typical Output Ripple V
OUT
Typical efficiency
PARAMETERS FOR -8V INVERTING CIRCUIT
Output Voltage V
OUT
Output Voltage V
OUT
Maximum Output Current
Maximum Output Current
Typical Output Ripple V
OUT
Typical efficiency
V
IN
= 2.7V, I
OUT
= 0mA to 35mA
V
IN
= 4.2V, I
OUT
= 0mA to 65mA
Vin = 2.7V
Vin = 4.2V
V
IN
= 3.3V, I
OUT
= 50mA
V
IN
= 4.2V, Vout = 15V@0mA and -8V@30mA
V
IN
= 2.7V, I
OUT
= 0mA to 25mA
V
IN
= 4.2V, I
OUT
= 0mA to 45mA
Vin = 2.7V
Vin = 4.2V
V
IN
= 3.3V , I
OUT
= 35mA
V
IN
= 4.2V, Vout = 15V@30mA and -8V turned off
CONDITION
VALUE
2.7v
4.2V
15V ±5%
15V ±5%
25mA
45mA
20mV
P–P
82%
VALUE
-8V ±5%
-8V ±5%
35mA
65mA
10mV
P–P
71%
output voltage. Both circuits are designed to demon-
strate the capacitor programmable Soft-Start feature,
advantages of the 1.1MHz constant switching fre-
quency and the internal 36V switches. Both outputs
on this demo circuit can be modified for higher volt-
ages. These circuits are intended for space-conscious
applications such as CCD Bias, TFT LCD Bias, OLED
Bias and +/- Rail Generation for Op Amps.
Design files for this circuit board are available. Call
the LTC factory.
LT is a trademark of Linear Technology Corporation
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 760
BOOST AND INVERTING DC/DC CONVERTERS
QUICK START PROCEDURE
Demonstration circuit 760A is easy to set up to evalu-
ate the performance of the LT3472EDD. 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.
4.
Check for the proper output voltages.
NOTE:
If there is no output, temporarily disconnect
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:
the load to make sure that the load is not set too
high.
5.
Once the proper output voltages are established,
JP1
On
adjust the loads within the operating range and ob-
serve the output voltage regulation, ripple voltage,
efficiency and other parameters.
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Ripple
VIN
GND
2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 760
BOOST AND INVERTING DC/DC CONVERTERS
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