STW82101B datasheet(33/68 Pages) STMICROELECTRONICS

33 / 68 page

STW82101B

General description

Doc ID 018503 Rev 3

33/68

IF amplifier

The integrated IF stage permits a 200-ohm load to be driven (typically a SAW filter) ensuring

high linearity.

It is an open collector stage (pin 31, 32) and should be biased to 5 V with choke inductors.

The typical output impedance is 200 ohms. The linearity performances are controlled by the

bits IFAMP[1:0]. In low current mode the configuration IFAMP[1:0]=’00’ (minimum linearity)

should be selected and the open collector stage can be biased to 3.3 V with choke

inductors.

8.1.13

Dual output current DAC

The STW82101B embeds a 10-bit Dual Output steering current DAC especially suited to

drive an external PIN diode attenuator. This provides power level calibration capability at the

RF input for the TX observation path applications.

The current sourced by the DAC is related to the REXT_DAC resistor according to the

following formulae (where VREXT_DAC is approximately 1.19 V):

With a 10 k

Ω REXT_DAC the FS current is approximately 2.8 mA.

Table 13.

Linearity performance against IFAMP[1:0] configuration (typical

condition)

IFAMP[1:0]

Linearity performance

18.5 dB

20.5 dB

22.5dB

24.5dB

IDAC

LSB

---

3VR

EXT_DAC

----------------------------------------

------

LSB DAC current

IDAC

---

3VR

EXT_DAC

----------------------------------------

1023

-------------

Full scale current

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