DC1037A - ANALOG DEVICES - Datasheet.Live

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1037

40V MICROPOWER DFN BUCK REGULATOR WITH INTEGRATED BOOST AND CATCH

DIODES

LT3470

DESCRIPTION

Demonstration circuit 1037 is a 40V micropower DFN

buck regulator featuring the LT®3470. The board is

optimized for 5V output at up to 200mA load current

for a steady state input voltage range of 5.5V to 40V.

With its wide input voltage range, high efficiency in-

ternal power switch, low dropout operation, hyster-

etic current-mode, integrated boost and catch diodes

and tiny SOT-23 package, the LT3470 is a very versa-

tile and powerful IC for DC/DC converters that require

extremely compact space, high efficiency and high

input voltage.

The LT3470 hysteretic control scheme allows all of

the components to be small, surface mount devices

while providing minimum output ripple voltage at all

load currents. The current-mode control topology

creates fast transient response and good loop stabil-

ity with a minimum number of external components.

The low resistance internal power switch achieves

high efficiencies of up to 82% at 12V input. The shut-

down jumper can be used to place the part in micro-

power shutdown, reducing supply current to less

than 1µA by driving the pin low. The internal boost

and catch diodes simplify layout and reduce compo-

nent count, providing the smallest solution possible.

The LT3470 datasheet gives a complete description of

the part, operation and applications information. The

datasheet must be read in conjunction with this Quick

Start Guide for demonstration circuit 1037. In par-

ticular, the datasheet section on ‘Thermal Calcula-

tions’ is important for estimating whether a given ap-

plication’s combination of input voltage, load current,

ambient temperature and frequency will cause the

LT3470 to exceed it’s absolute maximum rated junc-

tion temperature. The LT3470EDDB is assembled in a

small low profile DFN package. Proper board layout is

essential for maximum thermal performance. See the

datasheet section ‘Layout Considerations’.

Design files for this circuit board are available. Call

the LTC factory.

LT is a trademark of Linear Technology Corporation

QUICK START PROCEDURE

Demonstration circuit 1037 is easy to set up to evalu-

ate the performance of the LT3470. Refer to Figure 1

for proper measurement equipment setup and follow

the procedure below:

NOTE:

Make sure that the input voltage does not ex-

ceed 40V.

NOTE:

The shutdown jumper shunt is required to be

placed in the shutdown position or the VOUT ENABLE

position for proper operation.

NOTE:

Do not hot-plug the input voltage terminal VIN.

The absolute maximum voltage on VIN is 40V and

hot-plugging a power supply through wire leads to

the demonstration circuit can cause the voltage on

the extremely low-ESR ceramic input capacitor to ring

to twice its DC value. In order to protect the IC, a

higher ESR Aluminum Electrolytic capacitor is placed

at the input terminals. This may protect against some,

but not all, input transients due to hot-plugging with a

power supply.

See Application Note 88 for more de-

tails.

NOTE:

Connect the power supply (with power off),

load, and meters as shown in Figure 1.

After all connections are made, turn on input power

and verify that the output voltage is 5V.