M02061_17 Datasheet, PDF (37/45 Pages) M/A-COM Technology Solutions, Inc. – 3.3 or 5 Volt Laser Driver

M02061-12/-21
3.3 or 5 Volt Laser Driver
Rev V6
an external switch controlled by SHDWN_OUT) will immediately go open circuit and prevent any current from
passing through the laser.
Fault conditions checked by the M02061 include shorts to ground or V_CC of all pins which can increase the laser
modulation or bias current.
For an initialization sequence to be successful, all the fault detection monitors must signal that the chip is “healthy”.
When DIS goes low, pins are checked for shorts to ground or V_CC and a FAIL condition is latched if there is a fault.
If the state of the pins is OK, a one-shot at the reset pin begins a countdown which will latch a FAIL condition if the
bias current has not stabilized to an acceptable level during the one-shot time. The one-shot can be extended with
an external capacitor connected from the RESET pin to ground.
The one-shot¹ width is approximately:
T_ONE-SHOT = 3 ms + (0.3 ms/pF) x (external capacitance).
Figure 3-8. Safety Circuit Block Diagram, for SCB Pin Low
DIS
If chip is ‘healthy’, then Enable the
outputs and Start 3msec Reset
AND
AND
Pulse(one-shot)
AND
VccOK Detection:
5v Mode:
AND
Latch for
CrudeFaults
SRlatch
R: eset
Q
Vcc Pin
5v Hi/Lo Limits
Set
_
Vcc3 Pin
AND
3.3v Hi/Lo Limits
Latch for
Bias_OK
VCC_OK
ONE-SHOT:
Start
OR
SRlatch
3.3v Mode:
t=0
3ms + Tcap ^PULSE
R: eset
Q
Vcc Pin
5v Hi/Lo Limits
Vcc3 Pin
‘1’
AND
RESET
NOTE: Pulse stays high
if Reset pin is GNDed.
Set
_
optional cap for longer T_init
3.3v Hi/Lo Limits
CrudeFaults Detection:
OutP
Capc
MODset
IBout
> 300mV
> 300mV
> 300mV
> 300mV
CrudeFaults_OK
BiasOK Detection:
Window Compare:
HI Limit
MPCset
LOW Limit
OR
BIAS_OK
OUTPUT_ENABLE
FAILout
(open-collector)
37
1.The one-shot is actually comprised of an oscillator and 10-bit counter.
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