UBA1707TS datasheet(16/36 Pages) PHILIPS

16 / 36 page

1999 Feb 17

Philips Semiconductors

Product speciﬁcation

Cordless telephone, answering machine

line interface

UBA1707

General purpose switches (pins SWI1, SWI2 and

SWI3; bits SWC1, SWC2 and SWC3)

The UBA1707 is equipped with 3 general purpose

open-collector switches which short the pins SWI1, SWI2

and SWI3 to ground. They are respectively controlled by

bits SWC1, SWC2 and SWC3 and have an operating

voltage limited to 12 V. The outputs have to be current

biased.

For a bias current between 2 and 20 mA, the AC

impedance is 30

Ω maximum.

Serial interface (pins DATA, CLK and EN)

A simple 3-wire unidirectional serial bus is used to program

the circuit. The 3 wires of the bus are EN, CLK and DATA.

The data sent to the device is loaded in bursts framed by

EN. Programming clock edges (falling edges) and their

appropriate data bits are ignored until EN goes active

HIGH. The programmed information is loaded into the

addressed register when EN returns inactive (LOW) or left

open-circuit.

During normal operation, EN should be kept LOW. Only

the last 8 bits serially clocked into the device are retained

within the programming register. Additional leading bits

are ignored and no check is made on the number of clock

pulses. It can always capture new programming data even

during global power-down (bit PD at logic 1).

Data is entered with the most significant bit first.

The leading 6 bits make up the data field (bits D0 to D5)

while the trailing 2 bits are the address field

(bits ADO and AD1). The first bit entered is D5, the last

bit AD0. This organisation allows to send only the number

of bits of the addressed register.

Figure 16 shows the serial timing diagram. Table 1 gives

the list of registers.

When the supply voltage VCC drops below 2.5 V, all

by the power-up reset. At start-up, the circuit is in

power-down mode.

In the event that the IC is used in a noisy environment, it is

advised to periodically refresh the content of registers.

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