Micrel

MICRF211

March 2007

2

M9999-030107

(408) 944-0800

Pin Configuration

MICRF211AYQS

Pin Description

16-Pin

QSOP

Pin

Name

Pin Function

1

RO1

Reference resonator input connection to Colpitts oscillator stage. May also be driven by external reference

signal of 1.5V p-p amplitude maximum.

2

GNDRF

Negative supply connection associated with ANT RF input.

3

ANT

RF signal input from antenna. Internally AC coupled. It is recommended that a matching network with an

inductor -to-RF ground is used to improve ESD protection.

4

GNDRF

Negative supply connection associated with ANT RF input.

5

VDD

Positive supply connection for all chip functions.

6

SQ

Squelch control logic input with an active internal pull-up when not shut down.

7

SEL0

Logic control input with active internal pull-up. Used in conjunction with SEL1 to control the demodulator low

pass filter bandwidth. (See filter table for SEL0 and SEL1 in application section)

8

SHDN

Shutdown logic control input. Active internal pull-up.

9

GND

Negative supply connection for all chip functions except RF input.

10

DO

Demodulated data output.

11

SEL1

Logic control input with active internal pull-up. Used in conjunction with SEL0 to control the demodulator low

pass filter bandwidth. (See filter table for SEL0 and SEL1 in application section)

12

CTH

Demodulation threshold voltage integration capacitor connection. Tie an external capacitor across CTH pin

and GND to set the settling time for the demodulation data slicing level. Values above 1nF are

recommended and should be optimized for data rate and data profile.

13

CAGC

AGC filter capacitor connection. CAGC capacitor, normally greater than 0.47µF, is connected from this pin to

GND

14

RSSI

Received signal strength indication output. Output is from a buffer with 200

Ω typical output impedance.

15

NC

Not Connected (Connect to Ground)

16

RO2

Reference resonator input connection to Colpitts oscillator stage, 7pF, in parallel with low resistance MOS

switch-to-GND, during normal operation. Driven by startup excitation circuit during the internal startup control

sequence.