Linear Technology LTC3526 User manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT
1053A-A through 1053A-D
SYNCHRONOUS BOOST DC/DC CONVERTER
1
LTC3526/3526B/3526-2/3526B-2
DESCRIPTION
Demonstration circuits 1053A-A through 1053A-
D are high efficiency synchronous boost con-
verters capable of operating with an input volt-
age range from 0.9V to 5.5V. The 2X2 mm DFN
thermally enhanced package with a 1MHz
switching frequency (2MHz for LTC3526-2) and
the 500mA internal switches provide a very tiny
solution. The LTC3526 also features output dis-
connect and the input voltage can be greater or
less than the output voltage.
This demonstration circuit allows the user to
quickly evaluate the LTC3526 performance. In-
dividual jumpers are provided for selecting sev-
eral regulated output voltages and a low quies-
cent current shutdown. Terminals on the board
allow easy hookup to an input supply and out-
put load.
Design files for this circuit board are available.
Call the LTC factory.
LTC and Burst Mode are trademarks of Linear Technol-
ogy Corporation
Table 1. Typical Specifications (25°C)
Input Voltage Range V
IN
1V to 5V
1.8V V
OUT
V
IN
= 1V, I
OUT
= 100mA 1.8V ± 2.5%
3.3V V
OUT
V
IN
= 1.5V, I
OUT
= 100mA 3.3V ± 2.5%
5V V
OUT
V
IN
= 1.5V, I
OUT
= 100mA 5.0V ± 2.5%
Output Ripple Voltage (burst mode) V
IN
= 1.2V, V
OUT
= 1.8V I
OUT
= 1mA 45mV p-p
Output Ripple Voltage (fixed frequency) V
IN
= 1.2V, V
OUT
= 1.8V I
OUT
= 100mA 10mV p-p
Efficiency V
IN
= 1.2V, V
OUT
= 1.8V I
OUT
= 50mA 85%
Efficiency V
IN
= 2.5V, V
OUT
= 3.3V I
OUT
= 50mA 92%
V
Input
Power
Supply
A+
-V
A
Resistive
Load
Figure 1. Demonstration Circuit Test Setup

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT
1053A-A through 1053A-D
SYNCHRONOUS BOOST DC/DC CONVERTER
2
Table 2. Demonstration Circuit Board Information
1053A-A LTC3526EDC LCHW 1MHz Burst
1053A-B LTC3526BEDC LCNN 1MHz No Burst
1053A-C LTC3526-2EDC LCNM 2MHz Burst
1053A-D LTC3526B-2EDC LCNP 2MHz No Burst
Board
Number LTC Part Part Marking Frequency Mode
QUICK START PROCEDURE
There is one demonstration circuit board for
all four LTC3526 versions. The boards are
identified by the handwritten information on
the top of the pc board.
The boost converter can be evaluated using
the setup shown in Figure 1. Select one of the
three output voltages using jumpers JP1
through JP3. (With no jumpers installed, the
output voltage is 5V.) Set jumper JP4 in the
ON position and connect voltmeters and am-
meters as shown on the test setup. Connect a
power supply to the VIN and GND terminals
and a suitable load resistor between VOUT
and GND.
With a light load (1k resistor) at the output,
begin increasing the input power supply volt-
age. At approximately 850mV, the output will
rise to the selected regulated voltage. In-
crease the input voltage to approximately
1.5V and increase the load current.
Note the excellent load regulation when going
from a light load current to a heavier load, but
it is important to monitor the input voltage di-
rectly at the input terminals of the circuit
board. At very low input voltages, voltage
drops in the power supply wire, connections
and Ammeter will result in the input voltage at
the input terminals dropping below the mini-
mum voltage required for operation.
Additional pc board pads are provided for an
optional input bypass capacitor (C1). It may
be necessary when using long wires between
the power supply and circuit board, or for add-
ing a tantalum capacitor to minimize input
voltage transients that may occur when the
input is hot-switched. Also, pads on the board
backside are provided for adding a small
Schottky diode (D1) which can increase the
efficiency slightly under some conditions. But
adding a diode defeats the output disconnect
and short circuit protection features.
When verifying output ripple, it is important to
use the scope probe connection as shown in
Figure 3.
In Burst mode with light load current, the out-
put ripple voltage is higher than in non-burst
mode.
See LTC3526 Data Sheet for additional information
V
OUT
GND
Figure 3. Scope Probe Placement for
Measuring Output Ripple Voltage

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1053A-A
THROUGH D
SYNCHRONOUS BOOST DC/DC CONVERTER
3