Micrel, Inc.

SY58621L

January 2006

4

M9999-012006-B

Pin Description

Inputs

Pin Number

Pin Name

Pin Description

23

LOOPBACK

LOOPBACK Mode Control. TTL/CMOS control input. LOOPBACK is an active HIGH signal

used to control the LOOPBACK MUX. LOOPBACK is internally connected to a 25k

W pull-

20

/RXEN

Receiver Output Control. TTL/CMOS control input. /RXEN is an active LOW signal used to

enable the receiver outputs. /RXEN is internally connected to a 25k

W pull-down resistor and will

1, 2

RXIN, /RXIN

W. Input

will default to an indeterminate state if left open. See figure 6b.

7

/TXEN

Transmitter Output Control. TTL/CMOS control input. /TXEN is an active LOW signal used to

enable the transmitter output. /TXEN is internally connected to a 25k

W pull-down resistor and

14, 13

TXIN, /TXIN

Transmitter Differential Input. Input accepts AC- or DC-coupled differential signals as small as

W. Note that this input will

default to an indeterminate state if left open. See figure 6a.

9

TXVCTRL

Transmitter Output Swing Control. Input that controls the output amplitude of the transmitter.

to min swing. Refer to the “Interface Applications” and “Output Stage” sections for more

details.

11

TXVT

Input Termination Center-Tap. Each side of the transmitter differential input pair terminates to

the TXVT pin. The TXVT pin provides a center-tap to a termination network for maximum

interface flexibility. Refer to the “Input Stage” section for more details.