Micrel, Inc.

SY88232L/AL

June 2009

4

M9999-063009-A

Pin Description (continued)

Pin Number

Pin Name

Pin Function

12

APCSET

Bias current setting and control. The bias current is set by installing an external resistor from this

pin to ground or using a current source. Connect a 50kΩ resistor to GND for open loop operation.

13

MODSET

Modulation current setting and control. The modulation current is set by installing an external

resistor from this pin to ground or using a current source.

14

BIASMAX

Install a resistor between this pin and GND to set the maximum bias current for the closed loop

operation. The APC loop controls the bias current up to the level of BIASMAX. When the bias

current reaches the maximum value set through this pin, the driver continues to sink a current

equal to this maximum. For open loop operations, this pin sets the bias current.

15

MODMON

Modulation Current Monitor. Provides a current, which represents 1/100 of the modulation

current. Install a resistor between this pin and GND to convert that current to a voltage

proportional to the modulation current.

18

MOD-

Inverted modulation current output. Provides modulation current when input data is negative.

19

MOD+

Non-inverted modulation current output. Provides modulation current when input data is positive.

21

BIAS

Bias current output, sources current when /TXDIS is high. Connect to the cathode of the laser

through a resistor.

22

MD

Input from the laser monitoring photodiode. Connect to the anode of the laser photodiode for APC

operation.

23

BIASMON

Bias Monitor. Provides a current, which represents 1/50 of the bias current. Install a resistor

between this pin and GND to convert that current to a voltage.

24

RSSI

Received Signal Strength Indicator. Install a resistor from this pin to GND to get a voltage

proportional to the received signal.

25

APCFAULT

Indicates APC failure when High. Active High TTL/CMOS. Use a 10kΩ Pull up.

SY88232L: Post amplifier Non-inverting input data. Internally terminated with 50Ω to a reference

voltage.

27

RIN+

SY88232AL: Post amplifier Non-inverting input data. No internal termination.

SY88232L: Driver inverting input data. Internally terminated with 50Ω to a reference voltage.

28

RIN-

SY88232AL: Driver inverting input data. No internal termination.

30

ROUT-

Post Amplifier Complementary CML data output.

31

ROUT+

Post Amplifier true CML data output.

5, 8, 16, 24, 29

GND

Ground. Ground and exposed pad must be connected to the plane of the most negative potential.

17, 20, 32

Supply Voltage. Bypass with a 0.1µF//0.01µF low ESR capacitor as close to VCC pin as possible.