LTC1555/LTC1556
SIM Power Supply
and Level Translator
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DESCRIPTION
FEATURES
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The LTC®1555/LTC1556 provide power conversion and
level shifting needed for 3V GSM cellular telephones to
interface with either 3V or 5V Subscriber Identity Modules (SIMs). These parts contain a charge pump DC/DC
converter that delivers a regulated 5V to the SIM card.
Input voltage may range from 2.7V to 10V, allowing
direct connection to the battery. Output voltage may be
programmed to 3V, 5V or direct connection to the VIN pin.
Step-Up/Step-Down Charge Pump Generates 5V
Input Voltage Range: 2.7V to 10V
Output Current: 10mA (VIN ≥ 2.7V)
20mA (VIN ≥ 3V)
3V to 5V Signal Level Translators
> 10kV ESD on All SIM Contact Pins
Short-Circuit and Overtemperature Protected
Very Low Operating Current: 60µA
Very Low Shutdown Current: < 1µA
Soft Start Limits Inrush Current at Turn-On
Programmable 3V or 5V Output Voltage
650kHz Switching Frequency
Auxiliary 4.3V LDO/Power Switch (LTC1556 Only)
Available in a 16- and 20-Pin Narrow SSOP
A soft start feature limits inrush current at turn-on,
mitigating start-up problems that may result when the
input is supplied by another low power DC/DC converter.
The LTC1556 also includes an auxiliary LDO regulator/
power switch that may be used to power the frequency
synthesizer or other low power circuitry.
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APPLICATIONS
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Battery life is maximized by 60µA operating current and
1µA shutdown current. Board area is minimized by miniature 16- and 20-pin narrow SSOP packages and the need
for only three small external capacitors.
SIM Interface in GSM Cellular Telephones
Smart Card Readers
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATION
GSM Cellular Telephone SIM Interface
3V GSM
CONTROLLER
3V
1
2
3
4
VCC
VIN
2.7V TO 10V
LTC1555
5
6
7
8
CIN
CLK
RIN
RST
DATA
I/O
DDRV
VCC
DVCC
VIN
SS
C1 +
M1
M0
SIM
16
CLK
15
RST
14
I/O
13
12
11
10
C1 –
9
GND
10µF
+
0.1µF
VCC
5V ± 5%
IVCC ≤ 10mA
10µF
GND
1555/56 TA01
1
LTC1555/LTC1556
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ABSOLUTE MAXIMUM RATINGS
(Note 1)
VIN, DVCC to GND ..................................... – 0.3V to 12V
VCC to GND ............................................... – 0.3V to 12V
Digital Inputs to GND ................................ – 0.3V to 12V
LDO, CLK, RST, I/O to GND ........ – 0.3V to (VCC + 0.3V)
VCC, LDO Short-Circuit Duration ..................... Indefinite
Storage Temperature Range ................. – 65°C to 150°C
Temperature Range
LTC1555C/LTC1556C .............................. 0°C to 70°C
LTC1555I/LTC1556I ........................... – 40°C to 85°C
Extended Commercial Operating Temperature Range
(Note 2) ............................................. – 40°C to 85°C
Lead Temperature (Soldering, 10 sec).................. 300°C
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PACKAGE/ORDER INFORMATION
ORDER PART
NUMBER
TOP VIEW
CIN
1
16 CLK
RIN
2
15 RST
DATA
3
14 I/O
LTC1555CGN
LTC1555IGN
CIN
1
20 CLK
RIN
2
19 RST
DATA
3
18 I/O
DDRV
4
17 LDO
EN
5
16 VCC
DDRV
4
13 VCC
DVCC
5
12 VIN
FB
6
15 VIN
SS
6
11 C1 +
DVCC
7
14 C1 +
M1
7
10 C1 –
SS
8
13 C1 –
M0
8
9
GND
M1
9
12 GND
M0 10
11 GND
GN PACKAGE
16-LEAD PLASTIC SSOP
ORDER PART
NUMBER
TOP VIEW
LTC1556CGN
LTC1556IGN
GN PACKAGE
20-LEAD PLASTIC SSOP
TJMAX = 150°C, θJA = 95°C/ W
TJMAX = 150°C, θJA = 135°C/ W
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
VIN = 2.7V to 10V, DVCC = 1.8V to 5.5V, controller digital pins tied to DVCC, SIM digital pins floating, EN, FB pins tied to GND
(LTC1556), C1 = 0.1µF, COUT = 10µF unless otherwise specified.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
VIN Operating Voltage
●
2.7
10
V
DVCC Operating Voltage
●
1.8
5.5
V
100
135
µA
µA
1
2
25
µA
µA
µA
20
µA
1
µA
5.25
3.20
VIN
V
V
V
VIN Operating Current
2.7V ≤ VIN ≤ 5V, VCC = 5V, IVCC = 0
5V < VIN ≤ 10V, VCC = 5V, IVCC = 0
●
●
VIN Shutdown Current
M0, M1 = 0V, 2.7V ≤ VIN ≤ 5V
M0, M1 = 0V, 2.7V ≤ VIN ≤ 5V
M0, M1 = 0V, 5V < VIN ≤ 10V
●
DVCC Operating Current
M0, M1 = DVCC, CIN = 1MHz
●
DVCC Shutdown Current
M0, M1 = 0V
●
VCC Output Voltage
0 ≤ IVCC ≤ 10mA, 2.7V ≤ VIN ≤ 10V
0 ≤ IVCC ≤ 20mA, 3V ≤ VIN ≤ 10V
M0, M1 = DVCC
M0 = DVCC, M1 = 0
M0 = 0, M1 = DVCC
●
●
●
VCC Output Ripple
2
VIN = 3.6V, IVCC = 10mA, VCC = 5V
60
75
6
4.75
2.80
VIN – 0.3
5.00
3.00
75
mVP-P
LTC1555/LTC1556
ELECTRICAL CHARACTERISTICS
VIN = 2.7V to 10V, DVCC = 1.8V to 5.5V, controller digital pins tied to DVCC, SIM digital pins floating, EN, FB pins tied to GND
(LTC1556), C1 = 0.1µF, COUT = 10µF unless otherwise specified.
PARAMETER
CONDITIONS
VCC Short-Circuit Current
VCC Shorted to GND
●
MIN
Auxiliary LDO VOUT (VLDO)
EN = High, VCC = 5V, FB = LDO, ILDO = 5mA (LTC1556)
●
Auxiliary Switch Resistance
EN = High, VCC = 5V, FB = GND (LTC1556)
●
FB Input Resistance
(LTC1556)
4.00
TYP
MAX
12.5
40
4.3
4.55
18
30
UNITS
mA
V
Ω
200
Charge Pump fOSC
●
500
650
kΩ
800
kHz
µA
µA
Controller Inputs/Outputs, DVCC = 3V
Input Current (IIH, IIL)
M0, M1, SS, RIN, CIN
DDRV, EN
●
●
–1
–5
1
5
High Level Input Current (IIH)
DATA
●
– 20
20
µA
Low Level Input Current (IIL)
DATA
●
1
mA
High Input Voltage Threshold (VIH)
M0, M1, RIN, CIN, DDRV, EN
DATA
●
●
0.7 × DVCC
DVCC – 0.6
Low Input Voltage Threshold (VIL)
M0, M1, RIN, CIN, DDRV, EN
DATA
●
●
0.2 × DVCC
0.4
High Level Output Voltage (VOH)
DATA Source Current = 20µA, I/O = VCC
●
0.7 × DVCC
Low Level Output Voltage (VOL)
DATA Sink Current = – 200µA, I/O = 0V (Note 3)
●
DATA Pull-up Resistance
Between DATA and DVCC
●
DATA Output Rise/Fall Time
DATA Loaded with 30pF
V
V
V
V
V
0.4
V
20
28
kΩ
●
1.3
2
µs
IIH(MAX) = ±20µA
●
0.5 × VCC
0.7 × VCC
V
I/O Low Input Voltage Threshold (VIL)
IIL(MAX) = 1mA
●
0.4
V
High Level Output Voltage (VOH)
I/O, Source Current = 20µA, DATA or DDRV = DVCC
RST, CLK, Source Current = 20µA
●
●
0.8 × VCC
0.9 × VCC
V
V
Low Level Output Voltage (VOL)
I/O, Sink Current = – 1mA, DATA or DDRV = 0V (Note 3)
RST, CLK, Sink Current = – 200µA
●
●
I/O Pull-Up Resistance
Between I/O and VCC
●
13
SIM Inputs/Outputs, DVCC = 3V, VCC = 3V or 5V
I/O High Input Voltage Threshold (VIH)
6.5
10
0.4
0.4
V
V
14
kΩ
SIM Timing Parameters, DVCC = 3V, VCC = 5V
CLK Rise/Fall Time
CLK Loaded with 30pF
●
18
ns
RST, I/O Rise/Fall Time
RST, I/O Loaded with 30pF
●
1
µs
CLK Frequency
CLK Loaded with 30pF
●
5
MHz
VCC Turn-On Time
SS = DVCC, COUT = 10µF, IVCC = 0
SS = 0V, COUT = 10µF, IVCC = 0
1
6
ms
ms
VCC Discharge Time to 1V
IVCC = 0, VCC = 5V, COUT = 10µF
3
ms
The ● denotes specifications which apply over the specified temperature
range.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: C grade device specifications are guaranteed over the 0°C to 70°C
temperature range. In addition, C grade device specifications are assured
over the – 40°C to 85°C temperature range by design or correlation, but
are not production tested.
Note 3: The DATA and I/O pull-down drivers must also sink current
sourced by the internal pull-up resistors.
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LTC1555/LTC1556
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TYPICAL PERFORMANCE CHARACTERISTICS
Operating Current
vs Input Voltage
Shutdown Current
vs Input Voltage
120
VCC Output Voltage
vs Input Voltage (5V Mode)
5.2
20
IVCC = 10mA
M0 = DVCC
M1 = DVCC
COUT = 10µF
TA = 25°C
100
85°C
80
25°C
– 40°C
60
40
VCC OUTPUT VOLTAGE (V)
SHUTDOWN CURRENT (µA)
OPERATING CURRENT (µA)
NO EXTERNAL LOAD
15
10
85°C
25°C
5
5.1
5.0
4.9
– 40°C
2
6
8
4
VIN INPUT VOLTAGE (V)
10
0
4.8
6
8
4
VIN INPUT VOLTAGE (V)
2
10
1555/56 G01
VCC Output Voltage
vs Input Voltage (3V Mode)
2
6
8
4
VIN INPUT VOLTAGE (V)
10
1555/56 G02
1555/56 G03
VCC Output Voltage Turn-On Time,
SS Enabled
VCC Output Voltage Turn-On Time,
SS Disabled
3.1
1V/DIV
IVCC = 10mA
M0 = DVCC
M1 = 0V
COUT = 10µF
TA = 25°C
1V/DIV
VCC OUTPUT VOLTAGE (V)
3.2
3.0
2.9
VIN = 3V
SS = 0V
2.8
2
6
8
4
VIN INPUT VOLTAGE (V)
1555/56 G05
1ms/DIV
VIN = 3V
SS = DVCC
1ms/DIV
10
1555/56 G04
3V VCC Efficiency vs Input Voltage
5V VCC Efficiency vs Input Voltage
100
100
VCC = 5V
IVCC = 10mA
TA = 25°C
VCC = 3V
IVCC = 10mA
TA = 25°C
80
EFFICIENCY (%)
EFFICIENCY (%)
80
60
40
40
20
20
0
2
6
8
4
VIN INPUT VOLTAGE (V)
10
1555/56 G07
4
60
2
4
8
10
6
VIN INPUT VOLTAGE (V)
12
1555/56 G08
1555/56 G06
LTC1555/LTC1556
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PIN FUNCTIONS
LTC1555/LTC1556
CIN (Pin 1): Clock Input Pin from Controller.
RIN (Pin 2): Reset Input Pin from Controller.
DATA (Pin 3): Controller Side Data Input/Output Pin. Can
be used for single pin bidirectional data transfer between
the controller and the SIM card as long as the controller
data pin is open drain. The controller output must be able
to sink 1mA max when driving the DATA pin low due to
the internal pull-up resistors on the DATA and I/O pins. If
the controller data output is not open drain, then the
DDRV pin should be used for sending data to the SIM
card and the DATA pin used for receiving data from the
SIM card (see Figure 1).
DDRV (Pin 4): Optional Data Input Pin for Sending Data
to the SIM card. When not needed, the DDRV pin should
be left floating or tied to DVCC (an internal 1µA current
source will pull the DDRV pin up to DVCC if left floating).
DVCC (Pins 5/7): Supply Voltage for Controller Side Digital
I/O Pins. May be between 1.8V and 5.5V (typically 3V).
SS (Pins 6/8): Soft Start Enable Pin. A logic low will
enable the charge pump inrush current limiting feature.
A logic high will disable the soft start feature and allow
VCC to be ramped as quickly as possible upon start-up
and coming out of shutdown.
M1 (Pins 7/9): Mode Control Bit 1 (see Truth Table).
M0 (Pins 8/10): Mode Control Bit 0 (see Truth Table).
This table defines the various operating modes that may
be obtained via the M0 and M1 mode control pins.
Truth Table
M0
M1
MODE
0V
0V
Shutdown (VCC = 0V)
0V
DVCC
VCC = VIN
DVCC
0V
VCC = 3V
DVCC
DVCC
VCC = 5V
GND (Pins 9/11, 12): Ground for Both the SIM and the
Controller. Should be connected to the SIM GND contact
as well as to the VIN/Controller GND. Proper grounding
and supply bypassing is required to meet 10kV ESD
specifications.
C1– (Pins 10/12): Charge Pump Flying Capacitor Negative Input.
C1+ (Pins 11/13): Charge Pump Flying Capacitor Positive
Input.
VIN (Pins 12/14): Charge Pump Input Voltage Pin. Input
voltage range is 2.7V to 10V. Connect a 10µF low ESR
input bypass capacitor close to the VIN pin.
VCC (Pins 13/15): SIM Card VCC Output. This pin should
be connected to the SIM VCC contact. The VCC output
voltage is determined by the M0 and M1 pins (see Truth
Table). VCC is discharged to GND during shutdown
(M0, M1 = 0V). A 10µF low ESR output capacitor should
connect close to the VCC pin.
I/O (Pins 14/18): SIM Side I/O Pin. The pin is an open
drain output with a nominal pull-up resistance of 10k 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 when the part is in
shutdown.
RST (Pins 15/19): Level Shifted Reset Output Pin. Should
be connected to the SIM RST contact.
CLK (Pins 16/20): 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.
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LTC1555/LTC1556
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PIN FUNCTIONS
ground, the regulator acts as a ≤ 30Ω switch between VCC
and LDO.
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 1µA current source.
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 VCC is 5V (or greater). It is not
available when VCC = 3V. The LDO output may also be
used as a ≤ 30Ω power switch if the FB pin is grounded
or left floating. When used as a regulator, LDO must be
bypassed to GND with a ≥ 3.3µF capacitor. The LDO
output current will subtract from available VCC current.
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
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BLOCK DIAGRAM
VBATT
+
0.1µF
CIN
10µF
C1+
C1–
VIN
VCC
M1
STEP-UP/
STEP-DOWN
CHARGE PUMP
DC/DC
CONVERTER
M0
3V
VCC
COUT
10µF
SS
DVCC
VCC
RIN
RST
CIN
CLK
RST
CONTROLLER
SIM
20k
CLK
10k
DATA
I/O
I/O
1µA
OPTIONAL
DDRV
GND
GND
EN
1µA
1.23V
FB
153k
–
GND
+
LDO
4.3V
+
61k
LTC1555/LTC1556
LTC1556 ONLY
1555/56 BD
6
CLDO
10µF
FREQUENCY
SYNTHESIZER
POWER
LTC1555/LTC1556
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APPLICATIONS INFORMATION
The LTC1555/LTC1556 perform the two primary functions necessary for 3V controllers (e.g., GSM cellular
telephone controllers, smart card readers, etc.) to communicate with 5V SIMs or smart cards. They produce a
regulated 5V VCC supply for the SIM and provide level
translators for communication between the SIM and the
controller.
VCC Voltage Regulator
The regulator section of the LTC1555/LTC1556 (refer to
the Block Diagram) consists of a step-up/step-down charge
pump DC/DC converter. The charge pump can operate
over a wide input voltage range (2.7V to 10V) while
maintaining a regulated VCC output. The wide VIN range
enables the parts to be powered directly from a battery (if
desired) rather than from a 3V DC/DC converter output.
When VIN is less than the desired VCC the parts operate as
switched capacitor voltage doublers. When VIN is greater
than VCC the parts operate as gated switch step-down
converters. In either case, voltage conversion requires
only one small flying capacitor and output capacitor.
The VCC output can be programmed to either 5V or 3V via
the M0 and M1 mode pins. This feature is useful in
applications where either a 5V or 3V SIM may be used. The
charge pump VCC output may also be connected directly to
VIN if desired. When the charge pump is put into shutdown
(M0, M1 = 0), VCC is pulled to GND via an internal switch
to aid in proper system supply sequencing.
The soft start feature limits inrush currents upon start-up
or coming out of shutdown mode. When the SS pin is tied
to GND, the soft start feature is enabled. This limits the effective inrush current out of VIN to approximately 25mA
(COUT = 10µF). Inrush current limiting is especially useful
when powering the LTC1555/LTC1556 from a 3V DC/DC
output since the unlimited inrush current may approach
200mA and cause voltage transients on the 3V supply. However, in cases where fast turn-on time is desired, the soft
start feature may be overridden by tying the SS pin to DVCC.
Capacitor Selection
For best performance, it is recommended that low ESR
(< 0.5Ω) capacitors be used for both CIN and COUT to reduce
noise and ripple. The CIN and COUT capacitors should be
either ceramic or tantalum and should be 10µF or greater
(ceramic capacitors will produce the smallest output ripple).
If the input source impedance is very low (< 0.5Ω), CIN may
not be needed. Increasing the size of COUT to 22µF or greater
will reduce output voltage ripple—particularly with high VIN
voltages (8V or greater). A ceramic capacitor is recommended for the flying capacitor C1 with a value of 0.1µF or
0.22µF.
Output Ripple
Normal LTC1555/LTC1556 operation produces voltage
ripple on the VCC pin. Output voltage ripple is required for
the parts to regulate. Low frequency ripple exists due to
the hysteresis in the sense comparator and propagation
delays in the charge pump enable/disable circuits. High
frequency ripple is also present mainly from the ESR
(equivalent series resistance) in the output capacitor.
Typical output ripple (VIN < 8V) under maximum load is
75mV peak-to-peak with a low ESR, 10µF output capacitor. For applications requiring VIN to exceed 8V, a 22µF or
larger COUT capacitor is recommended to maintain maximum ripple in the 75mV range.
The magnitude of the ripple voltage depends on several
factors. High input voltages increase the output ripple
since more charge is delivered to COUT per charging cycle.
A large C1 flying capacitor (> 0.22µF) also increases ripple
in step-up mode for the same reason. Large output current
load and/or a small output capacitor (< 10µF) results in
higher ripple due to higher output voltage dV/dt. High ESR
capacitors (ESR > 0.5Ω) on the output pin cause high
frequency voltage spikes on VOUT with every clock cycle.
A 10µF ceramic capacitor on the VCC pin should produce
acceptable levels of output voltage ripple in nearly all
applications. However, there are several ways to further
7
LTC1555/LTC1556
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APPLICATIONS INFORMATION
reduce the ripple. A larger COUT capacitor (22µF or greater)
will reduce both the low and high frequency ripple due to
the lower COUT charging and discharging dV/dt and the
lower ESR typically found with higher value (larger case
size) capacitors. A low ESR ceramic output capacitor will
minimize the high frequency ripple, but will not reduce the
low frequency ripple unless a high capacitance value is
chosen (10µF or greater). A reasonable compromise is to
use a 10µF to 22µF tantalum capacitor in parallel with a 1µF
to 3.3µF ceramic capacitor on VOUT to reduce both the low
and high frequency ripple. An RC filter may also be used
to reduce high frequency voltage spikes (see Figure 1).
hundred milliseconds to completely shut down. To ensure
prompt and proper VCC shutdown, always force the M0
and M1 pins to a logic low state before shutting down the
DVCC supply (see Figure 2). Similarly, bring the DVCC
supply to a valid level before allowing the M0 and M1 pins
to go high when coming out of shutdown. This can be
achieved with pull-down resistors from M0 and M1 to
GND if necessary. (Note: shutting down the DVCC supply
with VIN active is not recommended with early date code
material. Consult factory for valid date code starting point
for shutting down the DVCC supply.)
Level Translators
VCC
+
15µF
TANTALUM
All SIMs and smart cards contain a clock input, reset input
and a bidirectional data input/output. The LTC1555/
LTC1556 provide level translators to allow controllers to
communicate with the SIM (see Figures 3a and 3b). The
CLK and RST inputs to the SIM are level shifted from the
controller supply rails (DVCC and GND) to the SIM supply
rails (VCC and GND). The data input to the SIM may be
provided two different ways. The first method is to use the
DATA pin as a bidirectional level translator. This configuration is only allowed if the controller data output pin is
open drain (all SIM I/O pins are open drain). Internal pullup resistors are provided for both the DATA pin and the
SIM
VCC
1µF
CERAMIC
LTC1555/
LTC1556
VCC
2Ω
10µF
SIM
VCC
10µF
LT1555/56 F01
Figure 1. VCC Output Ripple Reduction Techniques
Shutting Down the DVCC Supply
To conserve power, the DVCC supply may be shut down
while the VIN supply is still active. When the DVCC supply
is brought to 0V, weak internal currents will force the
LTC1555/LTC1556 into shutdown mode regardless of the
voltages present on the M0 and M1 pins. However, if the
M0 and M1 pins are floating or left connected to DVCC as
the supply is shut down, the parts may take several
LTC1555/LTC1556
CLK TO SIM
CIN
CLK
RST TO SIM
RIN
RST
DATA TO/FROM SIM
CONTROLLER
SIDE
DATA
I/O
DDRV
VCC
DVCC
SIM SIDE
1555/56 F3a
DVCC
Figure 3a. Level Translator Connections for
Bidirectional Controller DATA Pin
M0
0V
DVCC
LTC1555/LTC1556
M1
0V
CLK TO SIM
CIN
CLK
DVCC
RST TO SIM
RIN
RST
0V
DATA FROM SIM
DATA
I/O
DATA TO SIM
DDRV
VCC
DVCC
VCC
CONTROLLER
SIDE
VCC
0V
DVCC
SIM SIDE
1555/56 F3b
1555/56 F02
Figure 2. Recommended DVCC Shutdown and Start-Up Timing
8
Figure 3b. Level Translator Connections for
One-Directional Controller Side DATA Flow
LTC1555/LTC1556
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APPLICATIONS INFORMATION
I/O pin on the SIM side. The second method is to use the
DDRV pin to send data to the SIM and use the DATA pin to
receive data from the SIM. When the DDRV pin is not used,
it should either be left floating or tied to DVCC.
Level Translation with DVCC > VCC
It is assumed that most applications for these parts will
use controller supply voltages (DVCC) less than or equal
to VCC. In cases where DVCC is greater than VCC by more
than 0.6V or so, the parts’ operation will be affected in the
following ways: 1) A small DC current (up to 100µA) will
flow from DVCC to VCC through the DATA pull-up resistor,
N-channel pass device and the I/O pull-up resistor
(except when the part is in shutdown at which time DVCC
is disconnected from VCC by turning off the pass device).
If the VCC load current is less than the DVCC current, the
VCC output may be pulled out of regulation until sufficient
load current pulls VCC back into regulation. 2) When the
SIM is sending data back to the controller, a logic high on
the I/O pin will result in the DATA pin being pulled up to
[VCC + 1/3(DVCC – VCC)], not all the way up to DVCC. For
example, if DVCC is 5V and VCC is 3V, the DATA pin will
only swing from ≈ 0.1V to 3.67V when receiving data
from the SIM side.
Optional LDO Output
The LTC1556 also contains an internal LDO regulator for
providing a low noise boosted supply voltage for low power
external circuitry (e.g., frequency synthesizers, etc.) Tying
the FB pin to the LDO pin provides a regulated 4.3V at the
LDO output (see Figure 4). A 3.3µF (minimum) capacitor is
required to ensure output stability. A 10µF low ESR capacitor is recommended, however, to minimize LDO output
noise. The LDO output may also be used as an auxiliary
switch to VCC. If the FB pin is left floating or is tied to GND,
the LDO pin will be internally connected to the VCC output
through the P-channel pass device. The LDO may be disabled at any time by switching the EN pin from DVCC to GND.
The 4.3V LDO output is usable only when VCC is 5V (or
greater). It is not available when VCC = 3V.
EN
OFF
ON
1µA
VREF
FB 153k
61k
–
+
VCC = 5V
LDO
4.3V
+
ILDO
0mA to
10mA
10µF
TANT
1555/56 F04
Figure 4. Auxiliary LDO Connections (LTC1556 Only)
10kV ESD Protection
All pins that connect to the SIM (CLK, RST, I/O, VCC, GND)
withstand over 10kV of human body model (100pF/1.5kΩ)
ESD. In order to ensure proper ESD protection, careful
board layout is required. The GND pins should be tied
directly to a GND plane. The VCC capacitor should be
located very close to the VCC pin and tied immediately to
the GND plane.
9
LTC1555/LTC1556
U
PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
GN Package
16-Lead Plastic SSOP (Narrow 0.150)
(LTC DWG # 05-08-1641)
0.189 – 0.196*
(4.801 – 4.978)
16 15 14 13 12 11 10 9
0.229 – 0.244
(5.817 – 6.198)
0.150 – 0.157**
(3.810 – 3.988)
1
0.015 ± 0.004
× 45°
(0.38 ± 0.10)
0.007 – 0.0098
(0.178 – 0.249)
4
5 6
7
8
0.004 – 0.0098
(0.102 – 0.249)
0° – 8° TYP
0.016 – 0.050
(0.406 – 1.270)
* DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
10
0.053 – 0.068
(1.351 – 1.727)
2 3
0.008 – 0.012
(0.203 – 0.305)
0.025
(0.635)
BSC
GN16 (SSOP) 1197
LTC1555/LTC1556
U
PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
GN Package
20-Lead Plastic SSOP (Narrow 0.150)
(LTC DWG # 05-08-1641)
0.337 – 0.344*
(8.560 – 8.737)
20 19 18 17 16 15 14 13 12 11
0.229 – 0.244
(5.817 – 6.198)
0.150 – 0.157**
(3.810 – 3.988)
1
0.015 ± 0.004
× 45°
(0.38 ± 0.10)
0.007 – 0.0098
(0.178 – 0.249)
2 3
4
5 6
7
8
0.053 – 0.068
(1.351 – 1.727)
9 10
0.004 – 0.0098
(0.102 – 0.249)
0° – 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.008 – 0.012
(0.203 – 0.305)
0.025
(0.635)
BSC
* DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
GN20 (SSOP) 1197
11
LTC1555/LTC1556
U
TYPICAL APPLICATION
SIM Interface with Auxilary Power
+
10µF
3V GSM
CONTROLLER
3V
2
3
4
5
6
VCC
VIN
2.7V TO 10V
LTC1556
1
7
8
9
10
CIN
CLK
RIN
RST
CLK
19
RST
18
I/O
DDRV
LDO
EN
VCC
FB
VIN
DVCC
C1 +
14
SS
C1 –
13
M1
GND
GND
SIM
20
DATA
M0
4.3V
50mA
AUXILIARY LDO/POWER SWITCH
(FREQUENCY SYNTHESIZER)
I/O
17
16
VCC
5V ± 5%
IVCC ≤ 10mA
15
0.1µF
10µF
+
12
11
10µF
GND
1555/56 TA02
RELATED PARTS
PART NUMBER
DESCRIPTION
LTC1514-3.3/LTC1514-5
Regulated Step-Up/Step-Down Charge Pumps with Low Bat Comparator 3.3V and 5V Output Versions
COMMENTS
LTC1515 Series
Regulated Step-Up/Step-Down Charge Pumps with Reset Output
Adjustable, 3V/5V, 3.3V/5V Versions
LTC1516
Micropower, Regulated 5V Charge Pump DC/DC Converter
IOUT = 20mA (VIN ≥ 2V), IOUT = 50mA (VIN ≥ 3V)
LTC1517-5
Micropower, Regulated 5V Charge Pump DC/DC Converter
LTC1522 Without Shutdown and
Packaged in SOT-23
LTC1522
Micropower, Regulated 5V Charge Pump DC/DC Converter
IOUT = 20mA (VIN ≥ 3V), IQ = 6µA
LTC1550-4.1
Low Noise, Charge Pump Voltage Inverter
1mVP-P Ripple at 900kHz
LTC660
100mA Charge Pump DC/DC Converter
5V to – 5V at 100mA
12
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417 ● (408) 432-1900
FAX: (408) 434-0507● TELEX: 499-3977 ● www.linear-tech.com
15556f LT/TP 0398 4K • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 1997
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湘ICP备2023018690号
