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Final Electrical Specifications
LTC1756 Smart Card Interface
February 2000
FEATURES
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DESCRIPTION
The LTC(R)1756 universal Smart Card interface is fully compliant with ISO 7816-3 and EMV specifications. It provides the smallest and simplest interface circuit between a host microcontroller and general purpose Smart Cards. An internal charge pump DC/DC converter delivers regulated 3V or 5V to the Smart Card, while an on-chip level shifter allows a connection to a low voltage controller. All Smart Card contacts are rated for 10kV ESD, eliminating the need for external ESD protection devices. Input voltage may range from 2.7V to 5.5V, allowing direct connection to a battery. Automatic DC/DC converter soft start mitigates start-up problems that may result when the input power is provided by another regulator. Battery life is maximized by 75A operating current and 2A shutdown current. The 16-pin SSOP package minimizes PCB area for compact portable systems.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Fully ISO 7816-3 and EMV Compliant Buck-Boost Charge Pump Generates 3V or 5V 2.7V to 5.5V Input Voltage Range 3V 5V Signal Level Translator > 10kV ESD on All Smart Card Pins Dynamic Pull-Ups Deliver Fast Signal Rise Times Soft Start Limits Inrush Current at Turn On Very Low Operating Current: 75A Shutdown Current: < 2.5A Short-Circuit and Overtemperature Protected Available in 16-Pin SSOP Package
APPLICATIONS
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Handheld Payment Terminals Pay Telephones ATMs Key Chain Readers Smart Card Readers
TYPICAL APPLICATION
3.3V
SMART CARD PRESENT SWITCH
1 2 3 C3 10F C2 10F 4 5 6 7 8
PRES PWR GND VIN
5V/3V CARD READY C-
16 15 14 13 12 11 10 9
1756 TA01
N.O.
GND
LTC1756 VCC I/O RST CLK C+ DATA RIN CIN
VCC I/O
SMART CARD RST CLK
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.
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C1 0.68F
CONTROLLER
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LTC1756 ABSOLUTE MAXIMUM RATINGS
(Note 1)
PACKAGE/ORDER I FOR ATIO
TOP VIEW PRES PWR GND VIN VCC I/O RST CLK 1 2 3 4 5 6 7 8 16 5V/3V 15 CARD 14 READY 13 C - 12 C + 11 DATA 10 RIN 9 CIN
VIN to GND ............................................... - 0.3V to 6.0V VCC to GND .............................................. - 0.3V to 5.5V Digital Inputs to GND ..................... - 0.3V to VIN + 0.3V CLK, RST, I/O to GND ..................... - 0.3V to VCC + 0.3V VCC Short-Circuit Duration ............................... Indefinite Operating Temperature Range (Note 2) .. - 40C to 85C Storage Temperature Range ................ - 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C
ORDER PART NUMBER LTC1756EGN
GN PACKAGE 16-LEAD NARROW PLASTIC SSOP
TJMAX = 125C, JA = 135C/W
Consult factory for Industrial and Military grade parts.
The q denotes specifications which apply over the full specified temperature range, otherwise specificatons are at TA = 25C. VIN = 2.7V to 5.5V, unless otherwise noted.
PARAMETER Power Supply VIN Operating Voltage IVIN Operating Current IVIN Shutdown Current VCC Output Voltage IVCC Output Current ACTIVE State, IVCC = 0 IDLE State, VIN 3.6V IDLE State, 3.6V VIN 5.5V 5V/3V = VIN 5V/3V = 0V 5V/3V = 0V 5V/3V = VIN 5V/3V = 0V 5V/3V = VIN VCC Turn-On Time VCC Discharge Time to 0.4V Controller Input/Output DATA High Input Voltage Threshold (VIH) Low Input Voltage Threshold (VIL) High Level Output Voltage (VOH) Low Level Output Voltage (VOL) Output Rise/Fall Time Input Current (IIH/IIL) Source Current = 20A Sink Current = - 500A (Note 3) Loaded with 30pF, 10% to 90% PWR = VIN
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ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN 2.7
TYP
MAX 5.5
UNITS V A A A V V mA mA mA mA
75
150 2.5 10
4.75 2.80 55 65 55 40
5.00 3.00
5.25 3.20
3V VIN 5.5V 3V VIN 5.5V 2.7V VIN 5.5V 2.7V VIN 5.5V PWR to READY
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COUT = 10F,
2.7 100 VIN - 0.6 0.7 * VIN 0.5 * VIN 0.5 * VIN
12 250
IVCC = 0mA, VCC = 5V, COUT = 10F
0.3 0.3 0.5
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ms s V V V V s A
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LTC1756
The q denotes specifications which apply over the full specified temperature range, otherwise specificatons are at TA = 25C. VIN = 2.7V to 5.5V, unless otherwise noted.
PARAMETER RIN, CIN, PWR, 5V/3V High Input Voltage Threshold (VIH) Low Input Voltage Threshold (VIL) Input Current (IIH/IIL) READY, CARD Pull-Up Current (IOH) Low Level Output Voltage (VOL) Smart Card Input/Output I/O, VCC = 3V or 5V High Input Voltage Threshold (VIH) Low Input Voltage Threshold (VIL) High Level Output Voltage (VOH) Low Level Output Voltage (VOL) Rise/ Fall Time Short-Circuit Current CLK High Level Output Voltage (VOH) Low Level Output Voltage (VOL) CLK Rise/Fall Time CLK Frequency RST High Level Output Voltage (VOH) Low Level Output Voltage (VOL) RST Rise/Fall Time PRES High Input Voltage Threshold (VIH) Low Input Voltage Threshold (VIL) PRES Pull-Up Current PRES Debounce Time VPRES = 0V Proportional to the 0.68F Charge Pump Capacitor
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ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN 0.7 * VIN -1 250
TYP 0.5 * VIN 0.5 * VIN
MAX
UNITS V
0.2 * VIN 1
V A nA
Sink Current = - 20A IIH(MAX) = 20A IIL(MAX) = 1mA Source Current = 20A, DATA = VIN Sink Current = - 1mA, DATA = 0V (Note 3) Loaded with 30pF, 10% to 90% Shorted to VCC Source Current = 100A Sink Current = - 200A CLK Loaded with 30pF CLK Loaded with 30pF Source Current = 200A Sink Current = - 200A Loaded with 30pF
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0.3 0.6 * VCC 0.8 * VCC 0.3 0.5 3.5 VCC - 0.5 0.3 16 5 0.8 * VCC 0.3 0.5 0.7 * VIN 0.5 40 0.5 * VIN 0.5 * VIN 1 80 0.2 * VIN 5 0.5 * VCC 0.5 * VCC 0.8
V V V V V s mA V V ns MHz V V s V V A ms
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Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LTC1756 is guaranteed to meet performance specifications from 0C to 70C. Specifications over the - 40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls.
Note 3: The DATA and I/O pull-down drivers must sink up to 250A sourced by the internal current sources.
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LTC1756
PIN FUNCTIONS
PRES (Pin 1): (Input) Connects to the Smart Card acceptor's PRESENT indicator switch to detect if a card is inserted. This pin has a pull-up current source so that a normally open grounded switch can be detected with no external components. The pull-up current source is nonlinear, delivering higher current when the PRES pin is above 1V but very little current below 1V. This helps resist false card indications due to leakage current. PWR (Pin 2): (Input) A low on the PWR pin places the LTC1756 in the ACTIVE state enabling the charge pump. The READY pin indicates when the card supply voltage (VCC) has reached its final value and communication with the Smart Card is possible. The reset and clock channels are enabled after READY goes low. The I/O channel is also enabled only after READY goes low. The falling edge of PWR latches the state of the 5V/3V pin. After PWR is low, changes on the 5V/3V pin are ignored. GND (Pin 3): Ground Reference for the IC. This pin should be connected to a low impedance ground plane. Bypass capacitors for VIN and VCC should be in close proximity to the GND pin. VIN (Pin 4): Supply Voltage. May be between 2.7V and 5.5V. A 10F low ESR ceramic bypass capacitor is required on this pin for optimum performance. VCC (Pin 5): Regulated Smart Card Supply Voltage. This pin should be connected to the Smart Card VCC contact. The 5V/3V pin determines the VCC output voltage. The VCC pin is protected against short circuits by comparing the actual output voltage with an internal reference voltage. If VCC is below its correct level (for as little as 5s) the LTC1756 switches to the Alarm state (see the State Diagram). The VCC pin requires a 10F charge storage capacitor to ground. For optimum performance a low ESR ceramic capacitor should be used. During the Idle and Alarm states the VCC pin is rapidly discharged to ground to comply with the deactivation requirements of the EMV and ISO-7816 specifications. I/O (Pin 6): (Input/Output) Smart Card Side Data I/O Pin. This pin is used for bidirectional data transfer between the microcontroller and the Smart Card. It should be connected to the Smart Card I/O contact. The Smart Card I/O pin must be able to sink up to 250A when driving the I/O pin low due to the pull-up current source. The I/O pin becomes a low impedance to ground during the Idle state. It does not become active until READY goes low indicating that VCC is stable. Once READY is low, the I/O pin is protected against short circuits to VCC by current limiting to 5mA maximum. The DATA-I/O channel is bidirectional for half-duplex transmissions. Its idle state is H-H. Once an L is detected on one side of the channel the direction of transmission is established. Specifically, the side which received an L first is now the input, and the opposite side is the output. Transmission from the output side back to the input side is inhibited, thereby preventing a latch condition. Once the input side releases its L, both sides return to H, and the channel is now ready for a new L to be transmitted in either direction. If an L is forced externally on the output side, and it persists until after the L on the input side is released, this illegal input will not be transmitted to the input side because the transmission direction will not have changed. The direction of transmission can only be established from the idle (H-H) state and is determined by the first receipt of an L on either side. RST (Pin 7): (Output) Level-Shifted Reset Output Pin. This pin should be connected to the Smart Card RST contact. The RST pin becomes a low impedance to ground during the Idle state (see the State Diagram). The reset channel does not become active until the READY signal goes low indicating that VCC is stable. Short-circuit protection is provided on the RST pin by comparing RST with RIN. If these signals differ for several microseconds then the LTC1756 switches to the Alarm state. This fault checking is only performed after the VCC pin has reached its final value (as indicated by the READY pin). CLK (Pin 8): (Output) Level-Shifted Clock Output Pin. This pin should be connected to the Smart Card CLK contact. The CLK pin becomes a low impedance to ground during the Idle state (see the State Diagram). The clock channel does not become active until the READY signal goes low indicating that VCC is stable.
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LTC1756
PIN FUNCTIONS
Short-circuit protection is provided on the CLK pin by comparing CLK with CIN. If these signals differ for several microseconds then the LTC1756 switches to the Alarm state. This fault checking is only performed after the VCC pin has reached its final value (as indicated by the READY pin). The clock channel is optimized for signal integrity in order to meet the stringent duty cycle requirements of the EMV specification. Therefore, to reduce power in low power applications, clock stop mode is recommended when data is not being exchanged. CIN (Pin 9): (Input) Clock Input Pin from the Microcontroller. During the Active state this signal appears on the CLK pin after being level-shifted and buffered. RIN (Pin 10): (Input) Reset Input Pin from the Microcontroller. During the Active state this signal appears on the RST pin after being level-shifted and buffered. DATA (Pin 11): (Input/Output) Microcontroller Side Data I/O Pin. This pin is used for bidirectional data transfer between the microcontroller and the Smart Card. The microcontroller data pin must be open drain and must be able to sink up to 250A when driving the DATA pin low due to the pull-up current source. The DATA pin becomes high impedance during the Idle state (see the State Diagram). It does not become active until the READY signal goes low indicating that VCC is stable. C +, C - (Pins 12, 13): Charge Pump Flying Capacitor Terminals. Optimum values for the flying capacitor range from 0.68F to 1F. Best performance is achieved with a low ESR X7R ceramic capacitor. READY (Pin 14): (Output) Readiness Indicator of the Smart Card Supply Voltage (VCC). When the LTC1756 is placed in the Active state the soft start feature slowly ramps the VCC voltage. A low on the READY pin indicates that VCC has reached its final value. The READY pin is configured as an open-drain pull-down with a weak pull-up current source. The READY pin also indicates if the LTC1756 is in Alarm mode. The LTC1756 detects faults such as VCC underrange for at least 5s, overtemperature shutdown, CLK or RST invalid output levels and card removal during Active state. CLK or RST invalid and overtemperature faults are detected only after VCC has reached its final value. VCC underrange and card removal during Active faults are detected at any time during the Active period (i.e., once PWR = 0V). If the LTC1756 has been activated normally and VCC, the card voltage, has reached its final value then READY will go low indicating normal operation. If, following this, a fault occurs and the LTC1756 enters the Alarm state, the READY pin will return high. In the event that a fault precedes the activation of VCC, such as a direct short circuit from VCC to GND, the LTC1756 will attempt to operate until the fault is detected and then automatically shut down and enter the Alarm state. In this case the READY pin will never go low after the command to start the smart card is given (i.e., PWR = 0V). If the LTC1756 enters the Alarm state it can only be cleared by returning the PWR pin high. CARD (Pin 15): (Output) Level-Shifted and Debounced PRES Signal from the Smart Card Acceptor Switch. When a valid card indication appears, this pin communicates the presence of the Smart Card to the microcontroller. The CARD pin has an open-drain active pull-down with a weak pull-up current source. The debounce circuit ensures that a card has been present for a continuous period of at least 40ms before asserting CARD low. The CARD pin returns high within 50s of card removal. 5V/3V (Pin 16): (Input) Controls the output voltage (VCC) of the DC/DC converter during the Active state. A valid high sets VCC to 5V. A valid low sets VCC to 3V. The 5V/3V pin is latched on the falling edge of the PWR pin. When PWR is low, changes on the 5V/3V pin are ignored. To change the voltage on VCC the LTC1756 must first be returned to the Idle state by bringing the PWR pin high.
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LTC1756
BLOCK DIAGRA
PRES 1
PWR 2
GND 3 DC/DC CONVERTER AND CONTROL LOGIC
VIN 4
VCC 5
I/O 6
RST 7
CLK 8
*DYNAMIC PULL-UP CURRENT SOURCE
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VIN
16 5V/3V
15 CARD
14 READY
13 C -
12 C +
*
*
11 DATA
10 RIN
9 CIN
1756 BD
LTC1756
APPLICATIONS INFORMATION
10kV ESD Protection All Smart Card pins (CLK, RST, I/O, VCC and GND) can withstand over 10kV of human body model ESD in situ. In order to ensure proper ESD protection, careful board layout is required. The GND pin should be tied directly to a ground plane. The VCC capacitor should be located very close to the VCC pin and tied immediately to the ground plane. Capacitor Selection The style and value of capacitors used with the LTC1756 determine several parameters such as output ripple voltage, charge pump strength, Smart Card switch debounce time and VCC discharge rate. Due to the switching nature of a capacitive charge pump, low equivalent series resistance (ESR) capacitors are recommended for the capacitors at VIN and VCC. Whenever the flying capacitor is switched to the VCC charge storage capacitor, considerable current flows. The product of this high current and the ESR of the output capacitor can generate substantial voltage spikes on the VCC output. These spikes may cause problems with the Smart Card or may interfere with the regulation loop of the LTC1756. Therefore, ceramic or tantalum capacitors are recommended rather than higher ESR aluminum capacitors. Between ceramic and tantalum, ceramic capacitors generally have the lowest ESR. Some manufacturers have developed low ESR tantalum capacitors but they can be expensive and may still have higher ESR than ceramic types. Thus, while they cannot be avoided, ESR spikes will typically be lowest when using ceramic capacitors. For ceramic capacitors there are several different materials available to choose from. The choice of ceramic material is generally based on factors such as available capacitance, case size, voltage rating, electrical performance and cost. For example, capacitors made of Y5V material have high packing density, which provides high capacitance for a given case size. However, Y5V capacitors tend to lose considerable capacitance over the - 40C to 85C temperature range. X7R ceramic capacitors are more stable over temperature but don't provide the high packing density. Therefore, large capacitance values are generally not available in X7R ceramic. The value and style of the flying capacitor are important not only for the charge pump but also because they provide the large debounce time for the Smart Card detection channel. A 0.68F X7R capacitor is a good choice for the flying capacitor because it provides fairly constant capacitance over temperature and its value is not prohibitively large. The charge storage capacitor on the VCC pin determines the ripple voltage magnitude and the discharge time of the Smart Card voltage. To minimize ripple, generally, a large value is needed. However, to meet the VCC discharge rate specification, the value should not exceed 20F. A 10F capacitor can be used but the ripple magnitude will be higher leading to worse apparent DC load regulation. Typically a 15F to 18F Y5V ceramic capacitor is the best choice for the VCC charge storage capacitor. For best performance, this capacitor should be connected as close as possible to the VCC and GND pins. Note that most of the electrostatic discharge (ESD) current on the Smart Card pins is absorbed by this capacitor.
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LTC1756
APPLICATIONS INFORMATION
The bypass capacitor at VIN is also important. Large dips on the input supply due to ESR may cause problems with the internal circuitry of the LTC1756. A good choice for the input bypass capacitor is a 10F Y5V style ceramic Dynamic Pull-Up Current Sources The current sources on the bidirectional pins (DATA and I/O) are dynamically activated to achieve a fast rise time with a relatively small static current (Figure 1). Once a bidirectional pin is relinquished, a small start-up current begins to charge the node. An edge rate detector determines if the pin is released by comparing its slew rate with an internal reference value. If a valid transition is detected, a large pull-up current enhances the edge rate on the node. The higher slew rate corroborates the decision to charge the node thereby effecting a dynamic form of hysteresis. Once the node has reached the power supply voltage the internal comparator requires several hundred nanoseconds to reset. Pulling down on the pin before the reset delay expires will result in a momentary contention and a higher current flow. Therefore, the comparator delay sets the upper limit on the maximum data rate of the bidirectional channels to about 500kHz.
VCC OR VIN
ISTART
BIDIRECTIONAL PIN
Figure 1. Dynamic Pull-Up Current Sources
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Low Power Operation The LTC1756 is inherently a low power device. When there is no Smart Card present the supply current is less than 2.5A. When a Smart Card is present the LTC1756 operates with a quiescent current of only 75A, thus the majority of power is consumed by charge pump losses and the card itself. If the card can be made to consume less power during idle times a significant power savings will be achieved. Whenever possible Clock Stop Mode should be used (or alternatively a very low "idling" clock speed). Furthermore, in the Active state, the bidirectional pins should all be relinquished whenever possible since there is some static current flow when a bidirectional pin is pulled down. Overtemperature Fault Protection An overtemperature circuit disables the chip and places the LTC1765 in the Alarm state if the IC's junction temperature exceeds 150C.
+ -
V t
1756 F01
VREF
LTC1756
APPLICATIONS INFORMATION
Self-Start Mode By connecting the CARD pin to the PWR pin the LTC1756 can be made to start up automatically when a Smart Card is detected (Figure 2). In this mode, the READY pin becomes an interrupt signal indicating to the microcontroller that a Smart Card is present and that VCC, the charge pump voltage, is at its final value. The Smart Card remains powered as long as it is detected by the PRES pin. When the Smart Card is removed the LTC1756 will automatically be deactivated by the fault detection circuitry. Deactivation Sequence For maximum flexibility the Smart Card can be deactivated either manually or automatically. In manual mode the deactivation is controlled by explicitly manipulating the LTC1756 input and control pins (DATA, RIN and CIN followed by PWR). In automatic mode the PWR pin is used to perform the built-in deactivation sequence. Once PWR is brought high the built-in deactivation sequence occurs as follows:
DEACTIVATION DIRECTIVE
CARD
PWR READY TO MICROCONTROLLER
1756 F02
Figure 2. Self-Start Mode
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VCC
RST
RST = RIN
CLK
CLK = CIN
I/O
I/O = DATA
1755 F03
Figure 3. Deactivation Sequence
In the event of a fault, the LTC1756 automatically implements the built-in deactivation sequence.
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LTC1756
APPLICATIONS INFORMATION
IDLE DEACTIVATION PWR = 0V PWR = VIN ACTIVE
POWER OFF
PWR = VIN
Figure 4. LTC1756 State Diagram
State Definitions IDLE/DEACTIVATION VCC, RST, CLK, I/O = L READY, DATA = Z CARD = PRES Once the LTC1756 enters the Idle/Deactivation state the deactivation sequence begins. The deactivation sequence will continue until VCC is discharged to approximately 1V. An activation command (PWR = 0V) will only be acknowledged once this occurs. ALARM/DEACTIVATION The only possible next state is Idle/Deactivation which is achieved by disabling the LTC1756 via the PWR pin (i.e., PWR = VIN). The alarm indication can be cleared by rapidly cycling the PWR pin. However, a new activation cycle will not begin until VCC is or has dropped below approximately 1V. ACTIVE VCC = 3V or 5V (as determined by the 5V/3V pin) RST = RIN, CLK = CIN I/O, DATA = Ready for data (after READY becomes low) CARD = PRES FAULT TIMEOUT Same as Active except: The duration of a fault is being measured. If the fault duration exceeds 5s then the Alarm/Deactivation state follows. If the fault duration is less than 5s, then the device is returned to the Active state.
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PRES "0"
NO FAULT
FAULT
ALARM DEACTIVATION FAULT > 5s or PRES "0"
FAULT TIMEOUT
1756 F04
LTC1756
PACKAGE DESCRIPTION
0.007 - 0.0098 (0.178 - 0.249) 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
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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
0.009 (0.229) REF
0.229 - 0.244 (5.817 - 6.198)
0.150 - 0.157** (3.810 - 3.988)
1 0.015 0.004 x 45 (0.38 0.10) 0 - 8 TYP 0.053 - 0.068 (1.351 - 1.727)
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8 0.004 - 0.0098 (0.102 - 0.249)
0.008 - 0.012 (0.203 - 0.305)
0.0250 (0.635) BSC
GN16 (SSOP) 1098
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LTC1756 RELATED PARTS
PART NUMBER LTC1514/LTC1515 LTC1516 LTC1555/LTC1556 LTC1754-5 LTC1755 LTC1986 DESCRIPTION Micropower Step-Up/Step-Down Inductorless DC/DC Converters Micropower Regulated 5V Charge Pump SIM Power Supply and Level Translator 5V Charge Pump with Shutdown in SOT-23 Smart Card Interface with C4, C8 Pins 3V/5V SIM Power Supply in SOT-23 COMMENTS Regulated Output Up to 50mA, VIN from 2V to 10V, SO-8 Package 5V/50mA Output from 2V to 5V Input, S0-8 Package Step-Up/Step-Down Charge Pump + SIM Level Translators, >10kV ESD VIN from 2.7V to 5.5V, 50mA Output with VIN 3V VIN from 2.7V to 6V, 10kV ESD On All Smart Card Pins, 60A Operating Current VIN from 2.6V to 4.4V, 3V/5V Output at 10mA
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com
1756i LT/TP 0200 4K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 2000

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