Linear Technology 1172A User manual

LT
1965
1
DESCRIPTION
Demonstration circuit 1172A is a low dropout linear
regulator featuring LT®1965, w hich comes in 5-lead
T -220, 5-lead DD-PAK as w ell as the thermally en-
hanced 8-lead M S P and 8-lead 3mmX3mm DFN
packages. The DC1172A has an input voltage range
from 2.3 to 20V, and is capable of delivering up to
1.1A output current. perating quiescent current is
500µA , reducing to less than 1µA in shutdow n. The
DC1172A has a very low output noise, w hich makes it
ideal for logic pow er supplies, post regulator for
sw itching supplies and low noise instruments.
The LT1965 datasheet gives a complete description of
the part, operation and application information. The data-
sheet must be read in conjunction w ith this quick start
guide for demo circuit 1172A.
Design files for this circuit board are available. Call
the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation. ThinS T and
Pow erPath are trademarks of Linear Technology Corporation.
Perform ance Sum m ary ( TA = 2 oC )
PARAM ETER FOR BUCK REGULATOR CONDITION VALUE
M inimum Input Voltage 2.3V
M aximum Input Voltage 20V
utput Voltage Vout V
IN
=2.5V, I
UT
=1.1A
V
IN
=2.5V, I
UT
=1.1A
V
IN
=2.5V, I
UT
=1.1A
V
IN
=3.3V, I
UT
=1.1A
V
IN
=3.3V, I
UT
=1.1A
1.2V +/- 4%
1.5V +/- 4%
1.8V +/- 4%
2.5V +/- 4%
3.3V +/- 4%
M aximum utput Current 1.1A
Q U ICK STA RT PROCEDU RE
Demonstration circuit 1172A is easy to set up to evaluate
the performance of the LT1965. Refer to Figure 1 for
proper measurement equipment setup and follow the
procedure below :
1. Before proceeding to test, insert jumper JP1
into the FF position, and use V UT Select
jumper J1 for the desired output voltage 1.2V,
1.5V, 1.8V, 2.5V, 3.3V. If the output voltage is
different from the above values, use the USER
select option and install a resistor R5.
2. Apply input voltage across Vin to Gnd. Insert
jumper JP1 into the N position. Check for the
proper output voltage .
3. nce the proper output voltage is established,
adjust the load w ithin the operating range and
observe the output voltage regulation.
DEMO
C IR C U IT
1 1 7 2
A
Q U IC K S TAR T G U IDE
L T 1 9 6 5 E
DD
1 .1 A L o w Dro p o u t R e g u a to r

LT
1965
2
Figure 1. Proper M easurem ent Equipm ent Setup
Figure 2. M easuring Input or Output Ripple

LT
1965
3