MIC3002_10 Datasheet, PDF (27/65 Pages) Micrel Semiconductor – FOM Management IC with Internal Calibration

Micrel, Inc.
Figure 8. V_MOD Configured as Voltage Output
with Gain
Power ON and Laser Start-Up
When power is applied, then the MIC3002 initializes its
internal registers and state machine. This process takes
tPOR, about 50ms. Following tPOR, analog-to-digital
conversions begin, serial communication is possible, and
the POR bit and data ready bits may be polled. The first
set of analog data will be available tCONV after tPOR.
MIC3002s are shipped from the factory with the output
enable bit, OE, set to zero, off. The MIC3002’s power-up
default state, therefore, is APC off, VBIAS, VMOD, and
SHDN outputs disabled. VBIAS, VMOD, and SHDN will
be floating (high impedance) and the laser diode, if
connected, will be off. Once the device is incorporated
into a transceiver and properly configured, then the
shutdown states of SHDN, VBIAS and VMOD will be
determined by the state of the APC configuration and
OE bits. Tables 13, 14, and 15 illustrate the shutdown
states of the various laser control outputs versus the
control bits.
MIC3002
Configuration Bits
OE
SPOL
0
Don’t Care
1
0
1
1
Shutdown State
SHDN
Hi-Z
≈GND
≈V_DD
Table 13. Shutdown State of SHDN vs.
Configuration Bits
Configuration Bits
OE
INV
BIASREF
0 Don’t Care Don’t Care
1 Don’t Care
0
1 Don’t Care
1
VBIAS Shutdown State
VBIAS
Hi-Z
≈GND
≈V_DD
Table 14. Shutdown State of VBIAS vs.
Configuration Bits
Configuration Bits
OE
MODREF
0
Don’t Care
1
0
1
1
VMOD Shutdown State
VMOD
Hi-Z
≈GND
≈V_DD
Table 15. Shutdown State of VMOD vs.
Configuration Bits
In order to facilitate hot-plugging, the laser diode is not
turned on until t_INIT2 after Power-On. Following t_INIT2,
and assuming TXDISABLE is not asserted, the DACs
will be loaded with their initial values. Since t_CONV is
much less than t_INIT2, the first set of analog data,
including temperature, is available at t_INIT2. Temperature
compensation will be applied to the DAC values if
enabled. APC will begin if OE is asserted. (If the output
enable bit, OE, is not set, the V_MOD, V_BIAS, and SHDN
outputs will float indefinitely.) Figure 9 shows the power-
up timing of the MIC3002. If TXDISABLE is asserted at
power-up, the V_MOD and V_BIAS outputs will stay in their
shutdown states following MIC3002 initialization. A/D
conversions will begin, but the laser will remain off.
July 2007
27
M9999-073107-B
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