4

4867D–AUDR–01/08

ATR4256

4.

Input/Output Interface Circuits

4.1

PDO (Pin 1)

PDO is the buffer amplifier output of the PLL. The bipolar output stage is a rail-to-rail amplifier.

4.2

PD (Pin 2)

PD is the current charge pump output of the PLL. The current can be controlled by setting the

appropriate bits. The loop filter has to be designed corresponding to the chosen pump current

and the internal reference frequency. A recommendation can be found in the application circuit.

The charge-pump current can be chosen by setting Bit 71 and B

Figure 4-1.

Internal Components at PDO Connection

Table 4-1.

Current Charge-pump Output

IPD (µA)

B71

B70

25

0

0

100

0

1

500

1

0

2000

1

1

PD

VS

PDO

VS

VS