bd8918fv ROHM Co. Ltd., bd8918fv Datasheet - Page 8

• Manufacturer Part Number: bd8918fv
• Description: Ic Card Interface Ics With Built-in Low Noise Ldo Regulator
• Manufacturer: ROHM Co. Ltd.

●Function
© 2009 ROHM Co., Ltd. All rights reserved.
BD8918F,BD8918FV,BD8919F,BD8919FV
www.rohm.com
1) Power supply
2) Input voltage detector
3) Operation sequence
3-1) Wait mode
3-2) Card presence
Power supply pins are VDD and VDDP. Set VDD at the same voltage as the signal from the system controller side.
VDDP and CGND are for the 5V power source and GND, respectively, on the card side.
The IC remains in wait mode until the power on reset is released after the VDD supply voltage is increased over Vthd and
the VDDP supply voltage is increased over Vthp, making the CMDVCCB signal turn from H to L.
In this mode, the VDD and VDDP supply voltage detector (VDET), thermal shutdown circuit (TSD), reference circuit
(VREF) and crystal oscillation circuit (XT OSC) are activated.
IO_U is pulled up to VDD with an 11k resistor and all the card contact pins are at Lo level.
Card presence is detected by PRES pin. When the PRES pin is active, a card is assumed to be present.
When a card is present in wait mode, the card insertion identification pin, PRES (“H” active) becomes active and OFFB
becomes “H” after approx. 8ms (debounce time).
If a card is present before the VDD and VDDP power sources are applied and the internal reset is released, it is internally
reset and OFFB becomes “H” after the debounce time.
The PRES pin is pulled up to VDD with a 50k resistor.
The IC remains in wait mode until the power on reset is released 16ms after the VDD supply voltage is increased over
Vthd and the VDDP supply voltage is increased over Vthp, making the CMDVCCB signal turn from H to L.
Vthd=1.7V(typ)
Descriptions of transition times (example. Debounce time: 8msec) for the operation
sequences are adapted in the conditions of the following input frequency.
Table 1
Vthp=2.25V(typ)
PRES
8MHz (BD8918F/ FV), 16MHz (BD8919F/ FV)
“High” active
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Technical Note
2010.4 - Rev.D