FOA2322A Datasheet, PDF (17/37 Pages) Infineon Technologies AG – 3.2 Gbi t /s Laser Driver IC for Telecom and Datacom Applications

FOA2322A
Electrical Characteristics
14) _{If data input duty cycle falls below lower limit or exceeds upper limit the laser will be disabled by ISM circuit.}
On the other hand, the laser will be enabled whenever the data input duty cycle goes back to the allowed range.
Data input duty cycle refers to the quotient given by number of ones divided by number of zeros within serial
data stream. The ISM-circuit evaluates the mean value of the duty cycle (integrator). The cutoff frequency of
ISM f_ISM is defined for data pattern 1010 …. In case of data frequency is to small the ISM circuit will disable
the laser because of long High- or Low-series. The ISM-circuit can be deactivated by a 25 kΩ resistor from
CISM to V_EE. The ILM-circuit additionally is used for ac-coupled data inputs. It works as a peak detector. The
laser will be disabled if data are set to a static state. The cutoff frequency of ILM fILM is defined for data pattern
1010 …. (Specified value is for data input voltage swing of 400 mV).The ILM-circuit is direct AC-coupled to the
data input. So the cutoff frequency depends on data input swing. The ILM-circuit can be deactivated by a short
from CILM to V_CC.
15) _{A capacitor within this range programs the time (or frequency).}
16) _{Open collector output for pulling up a resistor to monitor the current.}
17) _{Difference and temperature drift of passive IC component parameters match to passive IC component}
parameters in other circuit parts.
18) _{The supervisor circuit will detect a failure condition if MD voltage exceeds VMDnom ± 2 dB range. VMDnom is}
given by nominal voltage level at MD which is set by V_MDR. The deviation is calculated with 20lg(V_MD/V_MDnom).
The deviation of optical power is calculated with 10lg(V_MD/V_MDnom).
19) _{The supervisor circuit will detect no failure condition if MD input voltage ranges from VMDnom - 1.2 dB to}
V_MDnom + 1.2 dB. V_MDnom is given by nominal voltage level at MD which is set by V_MDR. The deviation is
calculated with 20lg(V_MD/V_MDnom). The deviation of optical power is calculated with 10lg(V_MD/V_MDnom).
20) _{A failure condition will be reported by LF = H if this condition lasts for tFDEL. Minimal capacitor on CFDEL has}
to be chosen that the failure recognition time is longer than the setting time of the bias controller.
21) _{Time between LF high (or LEN high) and LDOFF high.}
22) _{At supply voltages below VCC threshold the laser diode bias and modulation current will be held disabled and}
LDOFF will be held high. Above the laser diode will be enabled after the Power On Delay.
23) _{The Power On Delay is the Reset time after VCC voltage has risen above the VCC reset threshold. During the}
Power On Delay the Laser diode bias and modulation current will be held disabled and LDOFF will be held
high.
24) _{Temperature and voltage drift are included.}
25) _{The minimal enable pulse width time for RST = L or RSTN = H or LEN = L has to be longer then tFDEL.}
26) _{Out of amPILOT and abPILOT a factor K = abPILOT/amPILOT can be defined, which is an important factor for the}
pilot control (for definition of am_PILOT and ab_PILOT see Figure 8). For most laser diodes the optimum value of
K is 1.44 (default value). If K is set close to factor 2 the modulation current and jitter may increase. If K is set
close to factor 1 the modulation current may decrease. In both cases a malfunction of laser control is possible.
A resistor between V_CC and RMRIP can be used for decreasing am_PILOT. Further a resistor between V_CC and
RBRIP can be used for decreasing ab_PILOT. So the factor K can be adjusted. For default factor K let RBRIP
and RMRIP connected to V_CC (= V_CCA).
Preliminary Data Sheet
13
2001-05