Micrel, Inc.

MICRF220

August 2010

2

M9999-082610-A

Pin Configuration

MICRF220AYQS

Pin Description

Pin

Number

Pin

Name

Pin Function

1

RO1

Reference resonator connection to the Pierce oscillator. May also be driven by external reference signal of

200mVp-p to 1.5V p-p amplitude maximum. Internal capacitance of 7pF to GND during normal operation.

2

GNDRF

Ground connection for ANT RF input. Connect to PCB ground plane.

3

ANT

Antenna Input: RF Signal Input from Antenna. Internally AC coupled. It is recommended to use a matching

network with an inductor-to-RF ground to improve ESD protection.

4

GNDRF

Ground connection for ANT RF input. Connect to PCB ground plane.

5

VDD

Positive supply connection for all chip functions. Bypass with 0.1μF capacitor located as close to the VDD pin

as possible.

6

SQ

Squelch Control Logic-Level Input. An internal pull-up (5μA typical) pulls the logic-input HIGH when the device

is enabled. A logic LOW on SQ squelches, or reduces, the random activity on DO pin when there is no RF

input signal.

7

SEL0

Demodulator Filter Bandwidth Select Logic-Level Input. This pin has an internal pull-up (3μA typical) when the

chip is on. Use in conjunction with SEL1 to control demodulation bandwidth.

8

SHDN

Shutdown Control Logic-Level Input. A logic-level LOW enables the device. A logic-level HIGH places the

device in low-power shutdown mode. An internal pull-up (5μA typical) pulls the logic input HIGH.

9

GND

Ground connection for all chip functions except for RF input. Connect to PCB ground plane.

10

DO

Data Output. Demodulated data output. A current limited CMOS output during normal operation, 25kΩ pull-

down is present when device is in shutdown.

11

SEL1

Demodulator Filter Bandwidth Select Logic-Level Input. This pin has an internal pull-up (3μA typical) when the

chip is on. Use in conjunction with SEL0 to Demodulation bandwidth.

12

CTH

Demodulation Threshold Voltage Integration Capacitor. Connect a 0.1μF capacitor from CTH pin-to-GND to

provide a stable slicing threshold.

13

CAGC

AGC Filter Capacitor. Connect a capacitor from this pin to GND. Refer to the AGC Loop and CAGC section for

information on the capacitor value.

14

RSSI

Received Signal Strength Indicator. The voltage on this pin is an inversed amplified version of the voltage on

CAGC. Output is from a switched capacitor integrating op amp with 250Ω typical output impedance.

15

NC

No Connect. Leave this pin floating.

16

RO2

Reference resonator connection to the Pierce oscillator. Internal capacitance of 7pF to GND during normal

operation.