Linear LTC3537 Quick Start Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1242A

600MA SYNCHRONOUS BOOST DC/DC CONVERTER AND 100MA LDO REGULATOR

LTC3537

DESCRIPTION

Demonstration circuit 1242A includes a high ef­ficiency synchronous boost converter, a low
dropout linear regulator and a low battery de­tector. With a light load, the boost converter can
startup with an input voltage as low as 680mV
and once started, the input can go as low as
500mV while maintaining a regulated output
voltage. With a 50mA load, the linear regulator
features a dropout voltage of less than 100mV.

Separate input terminals are provided for the
boost and linear regulator, and a jumper that
allows the linear regulator to be powered from
any one of three different sources.

Terminals and jumpers for shutting down or se­quencing each regulators output separately and
individual Power-Good outputs are included.
Jumpers are also provided for selecting a total
of six output voltages, three low battery volt­ages and a jumper to select BURST or PWM

Table 1. Typical Specifications (25°C)

operation. The 3X3 mm QFN thermally en­hanced package with a 2.2MHz switching fre­quency combined with the LDO regulator pro­vide a very tiny multi output solution. The
LTC3537 boost converter also features output
disconnect and the input voltage can be greater
or less than the output voltage.

This demonstration circuit allows the user to
quickly evaluate the LTC3537 performance.
Jumpers make selecting different output volt­ages and low battery thresholds simple while
terminals on the board allow easy hookup to
input supplies and output loads.

Design files for this circuit board are available.
Call the LTC factory.

LTC and Burst Mode are trademarks of Linear Technol­ogy Corporation

Conditions Limits
Input Voltage Range VIN 0.68V to 5.5V
Boost 1.8V V
Boost 3.3V V
Boost 5V V
Output Ripple Voltage (burst mode) VIN = 1.5V, V
Output Ripple Voltage (fixed frequency) VIN = 1.5V, V
Boost Efficiency VIN = 1.8V, V
LDO Regulator 1.5V V
LDO Regulator 3.0V V
LDO Regulator 3.3V V
LDO Regulator Drop Out Voltage V
Low Battery Threshold Voltage (dropping) 0.8V 800mV ± 5%
Low Battery Threshold Voltage (dropping) 1.7V 1.7V ± 5%
Low Battery Threshold Voltage (dropping) 3.0V 3V ± 5%

VIN = 1V, I

OUT

VIN = 1.5V, I

OUT

VIN = 1.5V, I

OUT

VIN = 5V, I

OUT

VIN = 5V, I

OUT

VIN = 5V, I

OUT

OUT

OUT

OUT

OUT

OUT

OUT

OUT

= 3.3V, I

= 100mA 1.8V ± 3.5%

= 200mA 3.3V ± 3.5%
= 200mA 5.0V ± 3.5%

= 3.3V I

OUT

= 3.3V I

OUT

= 3.3V I

OUT

= 50mA 1.5V ± 2.5%
= 50mA 3.0V ± 2.5%
= 50mA 3.3V ± 2.5%

= 50mA,

OUT

= 15mA 30mV p-p

OUT

= 200mA 10mV p-p

OUT

= 100mA 88%

OUT

V

drops 10%

OUT

100mV

1

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1242A

Select VOUT

Select VOUT

600MA SYNCHRONOUS BOOST DC/DC CONVERTER AND 100MA LDO REGULATOR

Figure 1. Demonstration Circuit Test Setup

LDO Input

BOOST Converter Input

A

Input

Power

Supply

+

-

PWRGOOD

STATUS Outputs

LDO & BOOST
ON/OFF Inputs

V

V

or

Select BOOST
ON/OFF/SEQ

Select
PWM
or BURST
Mode

QUICK START PROCEDURE

BOOST Regulator

Select
LDO
ON/OFF
or SEQ

Select
LOW
BAT
threshold

LDO Regulator

Low BAT

STATUS Outputs

V

Resistive
Loads

BOOST

A

V

A

V

LDO

Select
STATUS
power
source

EXT. STATUS
power source input,
select with JP4

Note:
resistors can
be replaced

Select LDO
input supply

with LEDs

The LTC3537 circuit can be evaluated using
the setup shown in Figure 1. Most of the fea­tures can be verified simply by placing jump­ers in various locations. It is recommended
that the LTC3537 data sheet be nearby for a
more complete explanation of the various fea­tures and specifications.

Using jumpers JP5 and JP6, select the de­sired output voltages (with no jumpers in­stalled, the output voltages are set for the
highest voltage). Enable each regulator by
placing jumpers JP7 and JP8 in the ON posi­tion and place the “LDO IN” jumper (JP3) to
the “VINB” (center) position which parallels
the LDO and BOOST supply inputs. Set the
“STATUS PWR” jumper (JP4) to the “VOUTB
position, which connects the open-drain
power good outputs and the low battery out­put pull-up resistors to the output of the boost
regulator. JP4 also allows an external voltage

applied to the STATUS PWR IN terminal to be
used for the pull-up resistors.

Connect voltmeters and ammeters as shown
in the Figure 1 test setup. Connect a power
supply to the VINBOOST and GND terminals
and a suitable load resistor between VOUT
BOOST and GND. Avoid excessive wire
lengths between the input power supply and
the demonstration board. Wire lengths greater
than 18 inches may require additional capaci­tance near the input terminals.

With a light load (1k resistor) at the output,
begin increasing the input power supply volt­age. At approximately 700mV, the output will
rise to the selected regulated voltage. When
the output voltage exceeds the input voltage
by at least 240mV, the converter powers itself
from the output instead of the input. This fea­ture allows the input voltage to drop as low as
500mV (at light loads) and still maintain a

2