Rainbow Electronics MAX3795 - Manual (Page 8)

MAX3795
1Gbps to 4.25Gbps Multirate VCSEL Driver
with Diagnostic Monitors
8 _______________________________________________________________________________________
Pin Description
PIN NAME FUNCTION
1, 10, 13 GND Ground
2 TX_DISABLE
Transmit Disable. Driver output is disabled when TX_DISABLE is high or left unconnected. The
driver output is enabled when the pin is asserted low.
3 IN+ Noninverted Data Input
4 IN- Inverted Data Input
5 FAULT
Fault Indicator. Open-drain output with ESD protection. FAULT is asserted high during a
fault condition.
6 SQUELCH
Squelch Enable. Squelch is enabled when the pin is set high. Squelch is disabled when the pin is
set low or left open.
7, 16, 20 V CC +3.3V Supply Voltage
8 TC1
Temperature Compensation Set Pin 1. A resistor placed between TC1 and TC2 (R TC ) programs the
temperature coefficient of the laser modulation current.
9 TC2
Temperature Compensation Set Pin 2. A resistor placed between TC1 and TC2 (R TC ) programs the
temperature coefficient of the laser modulation current.
11 MODSET
Modulation Set. A resistor connected from MODSET to ground (R MODSET ) programs the desired
modulation current amplitude.
12 PEAKSET
Peaking Current Set. A resistor connected between PEAKSET and ground (R PEAKSET ) programs the
peaking current amplitude. To disable peaking, leave PEAKSET open.
14 OUT- Inverted Modulation Current Output
15 OUT+ Noninverted Modulation Current Output
17 BIASSET
Bias-Current Set. When a closed-loop configuration is used, connect a 1.7k Ω resistor between
ground and BIASSET to program the maximum bias current. When an open configuration is used,
connect a resistor between BIASSET and ground (R
BIASSET ) to program the VCSEL bias current.
18 BIAS Bias-Current Output
19 BIASMON
Bias-Current Monitor. The output of BIASMON is a sourced current proportional to the bias current.
A resistor connected between BIASMON and ground (R
BIASMON ) can be used to form a ground-
referenced bias monitor.
21 COMP
Compensation Pin. A capacitor between COMP and MD compensates the APC. A typical value of
0.047µF is recommended. For open-loop configuration, short the COMP pin to GND to deactivate
the APC circuit.
22 MD Monitor Diode Connection
23 REF
Refer ence P i n. Refer ence m oni tor used for AP C . A r esi stor b etw een RE F and M D ( R P WRS E T ) p r og r am s
the p hotom oni tor cur r ent w hen the AP C l oop i s cl osed .
24 PWRMON
Average Power Monitor. The pin is used to monitor the transmit optical power. For open-loop
configuration, connect PWRMON to GND.
EP Exposed Pad
Ground. Must be soldered to the circuit board ground for proper thermal and electrical
performance. See the Layout Considerations section.