Datasheet
LTC1555L-1.8
5
V
IN
(Pin 12): Charge Pump Input Pin. May be between 2.6V
and 6V. There is no power-up sequencing requirement for
V
IN
with respect to DV
CC
.
V
CC
(Pin 13): SIM Card V
CC
Output. Should be connected
to the SIM V
CC
contact. The V
CC
output voltage is deter-
mined by the M0-M2 pins (see Table 1). V
CC
is discharged
to GND during shutdown (M0, M1 = 0V). A 2.2µF low ESR
ouptut capacitor should connect close to the V
CC
pin.
I/O (Pin 14): SIM Side I/O Pin. The pin is an open drain
output with a nominal pull-up resistance of 10kΩ and
should be connected to the SIM I/O contact. The SIM card
must sink up to 1mA max when driving the I/O pin low due
to the internal pull-up resistors on the I/O and DATA pins.
The I/O pin is held active low during shutdown.
RST (Pin 15): Level Shifted Reset Output Pin. Should be
connected to the SIM RST contact.
CLK (Pin 16): Level Shifted Clock Output Pin. Should be
connected to the SIM CLK contact. Careful trace routing is
recommended due to fast rise and fall edge speeds.
M0 M1 M2 OPERATING MODE
0V 0V 0V or DV
CC
Shutdown (V
CC
= 0V)
0V DV
CC
0V or DV
CC
V
CC
= V
IN
DV
CC
0V 0V V
CC
= 3V
DV
CC
0V DV
CC
V
CC
= 1.8V
DV
CC
DV
CC
0V or DV
CC
V
CC
= 5V
Table 1. Truth Table
PIN FUNCTIONS
UUU
M2 (Pin 6): Mode Control Bit 2 (see Table 1). (Pin 6 was
previously used for soft-start control on the LTC1555.)
M1 (Pin 7): Mode Control Bit 1 (see Table 1).
M0 (Pin 8): Mode Control Bit 0 (see Table 1).
GND (Pin 9): Ground for Both the SIM and the Controller.
Should be connected to the SIM GND contact as well as to
the V
IN
/controller GND. Proper grounding and supply
bypassing is required to meet 10kV ESD specifications.
C1
–
(Pin 10): Charge Pump Flying Capacitor Negative␣ Input.
C1
+
(Pin 11): Charge Pump Flying Capacitor Positive␣ Input.
BLOCK DIAGRA
W
DDRVOPTIONAL
1µA
I/O
DATA
20k 10k
CLK
CIN
RST
DV
CC
M2
1.8V
RIN
GND
M1
M0
V
IN
V
BATT
C
IN
1µF
V
CC
I/O
CLK
RST
GND
V
CC
C1
+
0.1µF
C1
–
STEP-UP/
STEP-DOWN
CHARGE PUMP
DC/DC
CONVERTER
SIMCONTROLLER
V
CC
C
OUT
2.2µF
UVLO
LTC1555L-1.8
1555L BD