QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 760
BOOST AND INVERTING DC/DC CONVERTERS
1
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
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
Table 1.
Performance Summary (T
A
= 25°C)
PARAMETERS FOR 15V BOOST CIRCUIT CONDITION VALUE
Minimum Input Voltage 2.7v
Maximum Input Voltage 4.2V
Output Voltage V
OUT
V
IN
= 2.7V, I
OUT
= 0mA to 25mA 15V ±5%
Output Voltage V
OUT
V
IN
= 4.2V, I
OUT
= 0mA to 45mA 15V ±5%
Maximum Output Current Vin = 2.7V 25mA
Maximum Output Current Vin = 4.2V 45mA
Typical Output Ripple V
OUT
V
IN
= 3.3V , I
OUT
= 35mA 20mV
P–P
Typical efficiency V
IN
= 4.2V, Vout = 15V@30mA and -8V turned off 82%
PARAMETERS FOR -8V INVERTING CIRCUIT VALUE
Output Voltage V
OUT
V
IN
= 2.7V, I
OUT
= 0mA to 35mA -8V ±5%
Output Voltage V
OUT
V
IN
= 4.2V, I
OUT
= 0mA to 65mA -8V ±5%
Maximum Output Current Vin = 2.7V 35mA
Maximum Output Current Vin = 4.2V 65mA
Typical Output Ripple V
OUT
V
IN
= 3.3V, I
OUT
= 50mA 10mV
P–P
Typical efficiency V
IN
= 4.2V, Vout = 15V@0mA and -8V@30mA 71%
