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BD8918FV-E2 Datasheet(PDF) 11 Page - Rohm |
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BD8918FV-E2 Datasheet(HTML) 11 Page - Rohm |
11 / 16 page Technical Note 11/15 BD8918F,BD8918FV,BD8919F,BD8919FV www.rohm.com 2010.4 - Rev.D © 2009 ROHM Co., Ltd. All rights reserved. 6) Card clock supply Card clock is supplied from the CLK pin dividing the input frequency of XTAL1 pin with the CLKSEL pin setting. The clock division switching time is within the 8 clocks of the XTAL1 signal. The input signal to the XTAL1 pin is made by a crystal oscillator (BD8918F/FV:8Hz, BD8919F/FV:16MHz) between the XTAL1 pin and XTAL2 pin or external pulse signal. When a crystal oscillator is used, the voltage between XTAL1 and XTAL2 may decrease to become close to “-1V”, which is not a problem. When an external pulse signal is applied to the XTAL1 pin (except for signal input by crystal oscillation), the duty of the XTAL1 pin should be 48% - 52% and the transition time of the XTAL1 pin should be within 5% of the signal cycle to ensure the duty factor of 45% - 55% at the CLK pin. Table 2 Clock frequency selection (fXTAL: Frequency at XTAL1) 7) RSTIN input, RST output The RSTIN input becomes effective after the CMDVCCB signal input turns to L from H, activation sequence is initiated and approximately 48 s after I/O TRANS turns ON. The RST output is released in approximately 472sec (max. 481 sec) after the CMDVCCB signal turns from H to L to output a signal based on the RSTIN input. 8) Fault detection When the following fault state is detected, the circuit enters the wait mode after it generates an internal alarm signal and is deactivated. If a card is not present, it remains in the wait mode. • When the VCC pin becomes less than 1.6V, or is loaded high current (TYP: 140mA) • When VDDP voltage is less than the threshold voltage (detected by supply voltage detector) • When a high temperature is detected by the thermal shutdown circuit • When the card is removed during operation or the card is not present from the beginning (PRES=L) 9) OFFB output The OFFB output pin indicates the IC is ready to operate. It is pulled up to VDD with a 20k resistor. When the IC is in the ready state, OFFB is High. After activation, the OFFB outputs OFF state (Lo) when a fault state is detected. When a card is present and CMDVCCB becomes High, the internal alarm is released and the OFFB output becomes High. Fig. 6 OFFB, CMDVCCB, PRES, VCC operation BD8918F/FV CLKSEL f clk BD8919F/FV CLKSEL f clk 1 XTAL f 1 2 XTAL f 0 2 XTAL f 0 4 XTAL f 端子ショート等による停止動作 カード取り外しによる停止動作 t debounce t debounce PRES OFFB VCC t debounce = typ 8ms CMDVCCB Shutdown by card removal Shutdown by short-circuiting of pins |
Similar Part No. - BD8918FV-E2 |
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Similar Description - BD8918FV-E2 |
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