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LTC1755 Datasheet(PDF) 6 Page - Linear Technology |
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LTC1755 Datasheet(HTML) 6 Page - Linear Technology |
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6 / 16 page  6 LTC1755/LTC1756 TYPICAL PERFOR A CE CHARACTERISTICS DVCC, VIN Supply Current In Shutdown DVCC INPUT VOLTAGE (V) 0 0 3.0 6.0 9.0 1.5 4.5 7.5 DVCC VIN 1 23 4 17556 G10 56 VIN = 3V TA = 25°C VIN Shutdown Current vs Input Voltage INPUT VOLTAGE (V) 0 0 0.2 0.4 0.6 0.8 1.0 1 23 4 17556 G11 56 DVCC = 0 TA = 25°C PI FU CTIO S 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 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. The activation state of the PRES pin can be set by the NC/NO pin so that both normally open (NO) and normally closed (NC) switches are easily recog- nized (see NC/NO pin description). DVCC sets the logic reference level for the PRES pin. PWR (Pin 2): (Input) A low on the PWR pin places the LTC1755/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 communica- tion with the Smart Card is possible. The reset and clock channels are enabled after READY goes low. The three I/ O channels are also enabled only after READY goes low, however they may be disabled separately via the CS pin (CS is not available on the LTC1756). 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. CS (Pin 3, LTC1755 Only): (Input) The CS pin enables the three bidirectional I/O channels of the LTC1755. When the I/O channels are disabled the Smart Card pins (I/O, AUX1, AUX2) are forced to logic one and the controller pins (DATA, AUX2IN, AUX1IN) are high impedance. CS can be brought low along with PWR when the device is first enabled, however communication with the Smart Card is inhibited until VCC reaches its final value as indicated by a low on the READY pin. CS does not affect the charge pump, CLK or RST channels. On the LTC1756, CS is internally connected to the PWR pin. DVCC sets the logic reference level for the CS pin. NC/NO (Pin 4, LTC1755 Only): (Input) This pin controls the activation level of the PRES pin. When it is high (DVCC) the PRES pin is active high. When it is low (GND) the PRES pin is active low. In either case the presence of a Smart Card is indicated by a low on the CARD output. When a ground side normally open (NO) switch is used the NC/NO pin should be grounded. When a ground side normally closed (NC) switch is used the NC/NO pin should be connected to DVCC. The LTC1756 is permanently config- ured to accept a normally open switch. LTC1755/LTC1756 |
Similar Part No. - LTC1755_15 |
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Similar Description - LTC1755_15 |
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