ZL10037

Data Sheet

11

Zarlink Semiconductor Inc.

The LEN bit enables the RFBYPASS output. With this bit set, the RF Bypass is active even if ‘software’ or

‘hardware’ power down has been selected.

The RFG bit controls the gain of the second section of RF gain control. With this bit set, the RF gain is reduced by

10dB. This setting would normally used when an external LNA is being used.

2.3

Base Band Registers

There are three registers that control the Base Band:

The bits BF[7:0] control the bandwidth of the baseband filter. An automatic adjustment routine synchronizes the

filter bandwidth to a reference frequency derived from the crystal.

The LF and SF bits disable the baseband filter adjustment. It is recommended that these bits are set after

programming the filter bandwidth to prevent interactions within the circuit. These bits must be reset to enable the

baseband filter bandwidth to be reprogrammed.

The BR[4:0] bits set the crystal reference divide ratio. This effectively determines the resolution setting of the

baseband filters. The baseband filter settings (BF[7:0]) can be calculated from the following equation.

See Section 3 Applications Information, for a typical programming example.

BR[4:0] = 0 is invalid

The BLF bit indicates that the baseband adjustment has completed and locked.

The control bits BG[3:0] define the gain of the Base Band post-filter amplifier. The following table shows the gain -

note this is relative gain. The 1.5 dB gain steps enable the baseband output level to be adjusted and optimise gain

distribution for different symbol rates.

Bit Field

Name

Default

Type

Description

7:0

BF[7:0]

0X3C

R/W

Base Band Filter Cut-Off Frequency

Table 10 - Register 5

Bit Field

Name

Default

Type

Description

7-

0

R/W

Test Mode

6

LF

0

R/W

Baseband Filter Adjust Disable

5

SF

0

R/W

Baseband Filter Adjust Disable

4:0

BR[4:0]

1000

R/W

Base Band Reference Division Ratio

Table 11 - Register 6

Bit Field

Name

Default

Type

Description

7

BLF

-

R

Base Band Lock Flag

6:3

BG[3:0]

0111

R/W

Base Band Gain Select

2:0

-

000

R/W

Test Modes

Table 12 - Register 7

1

(

−

=

(MHz)

Frequency

Crystal

0])

:

BR[4

*

5.088

*

(MHz)

bandwidth

Filter

0]

:

BF[7