MT88E45

Data Sheet

3

Zarlink Semiconductor Inc.

Figure 2 - Pin Connections

Pin Description

Pin # Name

Description

Voltage Reference (Output). Nominally Vdd/2. It is used to bias the Tip/Ring and Hybrid input op-

amps.

2IN1+

Tip/Ring Op-amp Non-inverting (Input).

3IN1-

Tip/Ring Op-amp Inverting (Input).

4GS1

Tip/Ring Gain Select (Output). This is the output of the Tip/Ring connection op-amp. The op-

amp should be used to connect the MT88E45B to Tip and Ring. The Tip/Ring signal can be

amplified or attenuated at GS1 via selection of the feedback resistor between GS1 and IN1-. FSK

demodulation (which is always on Tip/Ring) or CAS detection (for MEI or BT on-hook CLIP) of the

GS1 signal is enabled via the CB1 and CB2 pins. See Tables 1 and 2.

5

Vss

Power supply ground.

6OSC1 Oscillator (Input). Crystal connection. This pin can also be driven directly from an external clock

source.

7OSC2 Oscillator (Output). Crystal connection. When OSC1 is driven by an external clock, this pin

should be left open.

8CB0

Control Bit 0 (CMOS Input). This pin is used primarily to select the 3-wire FSK data interface

mode. When it is low, interface mode 0 is selected where the FSK bit stream is output directly.

When it is high, interface mode 1 is selected where the FSK byte is stored in a 1 byte buffer which

can be read serially by the application’s microcontroller.

The FSK interface is consisted of the DATA, DCLK and DR/STD pins. See the 3 pin descriptions

to understand how CB0 affects the FSK interface.

When CB0 is high and CB1, CB2 are both low the MT88E45B is put into a power down state

consuming minimal power supply current. See Tables 1 and 2.

9

DCLK 3-wire FSK Interface Data Clock (Schmitt Input/CMOS Output). In mode 0 (when the CB0 pin

is logic low) this is a CMOS output which denotes the nominal mid-point of a FSK data bit.

In mode 1 (when the CB0 pin is logic high) this is a Schmitt trigger input used to shift the FSK data

byte out to the DATA pin.

1

2

3

4

5

6

9

10

20

19

18

17

16

15

14

13

IN1+

IN1-

GS1

Vss

OSC1

DCLK

DATA

IN2+

IN2-

GS2

CB2

CB1

Vdd

CD

ST/GT

MT88E45B

7

OSC2

8

CB0

12

11

EST

DR/STD