LTC1555 Linear Technology, LTC1555 Datasheet - Page 6

• Manufacturer Part Number: LTC1555
• Description: SIM Power Supply and Level Translator
• Manufacturer: Linear Technology

BLOCK
PIN
LTC1555/LTC1556
LTC1556 Only
EN (Pin 5): Auxiliary LDO/Power Switch Enable Pin. A
logic high on this pin from the controller will enable the
auxiliary LDO output. When the LDO is disabled, the LDO
output will float or be pulled to ground by the load. If left
floating, the EN pin will be pulled down to GND by an
internal 1 A current source.
FB (Pin 6): Auxiliary LDO Feedback Pin. When FB is
connected to the LDO pin (Pin 17), the LDO output is
regulated to 4.3V (typ). If the FB pin is left open or tied to
6
U
FUNCTIONS
U
DIAGRAM
CONTROLLER
LTC1555/LTC1556
LTC1556 ONLY
U
V
CC
W
V
OPTIONAL
BATT
3V
+
C
10 F
IN
V
M1
M0
SS
DV
RIN
CIN
DATA
DDRV
EN
FB
IN
CC
153k
1 A
61k
1.23V
20k
1 A
CHARGE PUMP
–
+
STEP-DOWN
CONVERTER
STEP-UP/
DC/DC
C1
0.1 F
+
ground, the regulator acts as a 30 switch between V
and LDO.
LDO (Pin 17): LDO Output Pin. This pin should be tied to
the FB pin for 4.3V LDO operation. The 4.3V LDO output
is usable only when V
available when V
used as a 30 power switch if the FB pin is grounded
or left floating. When used as a regulator, LDO must be
bypassed to GND with a
output current will subtract from available V
C1
–
10k
GND
GND
RST
LDO
V
CLK
I/O
CC
CC
= 3V. The LDO output may also be
4.3V
1555/56 BD
CC
+
C
10 F
OUT
is 5V (or greater). It is not
C
10 F
LDO
3.3 F capacitor. The LDO
V
RST
CLK
I/O
GND
CC
FREQUENCY
SYNTHESIZER
POWER
SIM
CC
current.
CC