Micrel, Inc.

SY88808L

June 2010

4

M9999-063010-A

hbwhelp@micrel.com or (408) 955-1690

Pin Description

Pin Number

Pin Name

Pin Function

1, 28

TXQ, /TXQ

Differential Transmitter Output: This CML output pair is designed to drive 50

Ω signals with

variable output swing.

2, 13, 16, 27

VCC

Positive power supply: Connect to 3.3V power supply. Bypass with 0.1

μF||0.01μF low-ESR

capacitors as close to VCC pins as possible.

3, 19

NC

No connect.

4

TXSW

Programmable Swing Input pin: This input pin allows the user to set variable output swing.

This pin can be programmed via external potentiometer (or a resistor) to output a swing from

5, 10, 11, 12

24, 25

RXEQDC,

RXEQMF,

RXEQHF,

RXEQUHF,

TXEQHF,

TXEQUHF

Programmable EQ: Equalization circuit can recover degraded signals after long traces of FR4

board. Equalization can be programmed via an external potentiometer (or resistor). This

equalization scheme is optimized to recover degraded signal from any length of transmission

line. The receiver of the RX channel can equalize up to 36” FR4 or 10m 26AWG cable. The

receiver of the TX channel can equalize up to 9” FR4 or 3m 26AWG cable. RXEQDC,

RXEQMF, RXEQHF, and RXEQUHF control DC, medium, high, and ultra high components of

input data signals of RX channel respectively. TXEQHF and TXEQUHF control high and ultra

high components of input data signals of TX channel respectively. See “Programmable

Equalization” table for details.

6, 9, 20, 23

GND, Exposed Pad

Ground: Ground pins and exposed pad must be connected to the same ground plane.

7, 8

RXIN, /RXIN

Differential Receiver Input: This input pair is the differential input to the receive channel. It

line. The input signal is fed in to an equalization circuit. The loss-of-signal (LOS) level includes

a small amount of hysteresis to prevent the LOS output from oscillating when no signal is

present.

14, 15

/RXQ, RXQ

50

Ω.

17, 26

/RXEN, /TXEN

Single-Ended Input: TTL/CMOS compatible control input for the output pairs. The disable pins

are internally connected to a 25k

Ω pull-up resistor and will default to a logic HIGH state

(Disable) if left open. When disabled, the Q goes LOW, and /Q goes HIGH. Default threshold

18

LOS

Single-Ended Output: This TTL/CMOS output signal switches LOW when the input signal of

the receiver channel is valid and switches HIGH when the input signal is not valid. LOS is an

open-collector output.

21, 22

TXIN, /TXIN

Differential Transmitter Input: This input pair is the differential input to the transmit channel

and accepts differential AC-coupled signals which are fed in to equalization circuit. Input

swing is recommended to be

≥150mV

outputs.