Linear Technology DC2041A Manual

Description
Demonstration circuit 2041A is a switched-capacitor
step-down power supply featuring the
LTC3255 has the ability to step down voltage 2:1 to ef-
ficiently regulate output voltages less than half the V
voltage reducing the input current needed. As V
below twice V , the LTC3255 will automatically switch
OUT
to 1:1 mode.
The LTC3255 also has an integrated shunt regulator al-
lowing it to provide a regulated output from a 4mA to
20mA current loop.
performance summary
PARAMETER
Input Supply Range
V
OUT
I
OUT
7.4mA DC Supply from 4mA to 20mA Current Loop
+
4mA TO 20mA INPUT
1µF
>10V COMPLIANCE
–
Wide V
50mA Step-Down Charge Pump
LTC 3255. The
®
reduces
IN
Specifications are at T
CONDITIONS
Shunt Jumper = OFF (SHUNT = GND)
Shunt Jumper = ON (SHUNT = BIAS) I
1µF
+ –
C C
V V
IN OUT
EN LTC3255 220k
PGOOD PGOOD
SHUNT
BIAS GND FB
0.1µF
DEMO MANUAL DC2041A
Range Fault Protected
IN
The LTC3255 is a robust device that can survive reverse-
polarity input supplies with current limit and overtem-
perature protection.
IN
Refer to the LTC3255 data sheet for more details on the
electrical and timing specifications.
Design files for this circuit board are available at
http://www.linear.com/demo
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
= 25°C
A
= 4mA
IN
OUTPUT
3.3V
7.4mA
10µF
2.15M
1.21M
DC2041A F01
LTC3255EMSE
MIN TYP MAX
4 48
2.4 12.5
50
7.4 7.8
Available Output Current
vs Input Current
40
37
34
31
28
AVAILABLE
25
INCREASED
I
OUT
I CAPABILITY
22
OUT
19
16
13
INPUT
10
CURRENT
7
4
4 6 8 10 12 14 16
INPUT CURRENT (mA)
UNITS
V
V
mA
mA
18 20
DC2041A F02
dc2041af
1