AS3909 datasheet(64/77 Pages) AMSCO

64 / 77 page

AS3909/AS3910 – 64

ams Datasheet, Confidential: 2013-Oct [3-02]

A p pl i c at io n I n f o r m at i o n

Calibrate Antenna Resonance3

In order to implement the antenna LC tank calibration binary

weighted trimming capacitors have to be connected between

the two coil terminals to the pads TRIM1_3 to TRIM1_0 and

TRIM2_3 to TRIM2_0. In case single driver is used only the pads

TRIM1_3 to TRIM1_0 are used, pads TRIM2_3 to TRIM2_0 are left

open.

Figure 51 depicts connection of the trim capacitors for both,

single and differential driving. The TRIM pads contain the

HVNMOS switch transistors to VSS. During trimming procedure

the resonance frequency is adjusted by connecting some of the

trimming capacitors to VSS and leaving others floating.

The switches of the same binary weight are driven from the

same source and are both on or off (the switches TRIM1_2 and

TRIM2_2 are for example both either on of off ).

The breakdown voltage of the HVNMNOS switch transistors is

30V, which limits the maximum peak to peak voltage on LC tank

in case trimming is used. The on resistance of TRIM1_0 and

TRIM2_0 switch transistors which are meant to be connected

to LSB trimming capacitor is typ 50

Ω at 3V VSP, the on resistance

of other pads is binary weighted (the on resistance of TRIM1_3

and TRIM2_3 is 6.25

Ω).

Figure 51:

Connection of Trimming Capacitors to the Antenna LC Tank in case of Single (left) and Differential

Driving (right)

3. Only available in AS3910.

TRIM 1_0

TRIM 1_1

TRIM 1_2

TRIM 1_3

RF01

RF02

RFI 1

RFI 2

Antenna

TRIM 2_3

TRIM 2_2

TRIM 2_1

TRIM 2_0

TRIM 1_0

TRIM 1_1

TRIM 1_2

TRIM 1_3

RF01

RF02

RFI 1

RFI 2

½ Antenna

TRIM 2_3

TRIM 2_2

TRIM 2_1

TRIM 2_0

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