MIC3001GML Micrel Inc, MIC3001GML Datasheet - Page 22

• Manufacturer Part Number: MIC3001GML
• Description: IC FOM MANAGEMENT W/CALIBR 24MLF
• Manufacturer: Micrel Inc
• Type: Transceiverr

Specifications of MIC3001GML

• Protocol: SDHj Sonet
• Voltage - Supply: 3 V ~ 3.6 V
• Mounting Type: Surface Mount
• Package / Case: 24-MLF®, QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Number Of Drivers/receivers: -
• Other names: 576-1753-5; MIC3001GML

Micrel, Inc.
C/ ADC Result Registers Reading
In the present revision of MIC3001, the ADC result
registers should be read as 16 bit registers under internal
calibration while under external calibration they should be
read as 8 bit registers at the MSB address. For example,
TX power should be read under internal calibration as 16
bits at address A2 h : 66–67 and under external calibration
as 8 bits at address A2 h : 66 h .
RXPOT
A
potentiometer is provided for adjusting the gain of the
receive power measurement signal chain in the analog
domain. Five bits in the RXPOT register are used to set
and adjust the position of potentiometer. RXPOT
functions as a programmable divider or attenuator. It is
adjustable in steps from 1:1 (no divider action) down to
1/32 in steps of 1/32. If RXPOT is set to zero, the divider
is bypassed completely. There will be no scaling of the
input signal, and the resistor network will be disconnected
from the VRX pin. At all other settings of RXPOT, there
will be a 32kΩ (typical) load seen on VRX.
Laser Diode Bias Control
The MIC3001 can be configured to generate a constant
bias current using electrical feedback, or regulate average
transmitted optical power using a feedback signal from a
monitor photodiode, see Figure 4. An operational
amplifier is used to control laser bias current via the V
output. The VBIAS pin can drive a maximum of ±10mA.
An external bipolar transistor provides current gain. The
polarity of the op amp’s output is programmable
BIASREF in OEMCFG1 in order to accommodate either
NPN or PNP transistors that drive common anode and
common cathode laser, respectively. Additionally, the
polarity of the feedback signal is programmable for use
with either common-emitter or emitter-follower transistor
circuits.
August 2004
programmable,
Figure 3. RXPOT Block Diagram
non-volatile
digitally
controlled
BIAS
Furthermore, the reference level for the APC circuit is
selectable to accommodate electrical, i.e., current feedback,
or optical feedback via a monitor photodiode. Finally, any
one of seven different internal feedback resistors can be
selected. This internal resistor can be used alone or in
parallel with an external resistor. This wide range of
adjustability (50:1) accommodates a wide range of
photodiode current, i.e, wide range of transmitter output
power. The APC operating point can be kept near the mid-
scale value of the APC DAC, insuring maximum SNR,
maximum effective resolution for digital diagnostics, and the
widest possible DAC adjustment range for temperature
compensation, etc. See Figure 5.
The APCCAL bit in OEMCAL0 is used to turn the APC
function on and off. It will be turned off in the MIC3001’s
default state as shipped from the factory. When APC is on,
the value in the selected APCSETx register is added to the
signed value taken from the APC look-up table and loaded
into the V
be written directly via the V
up table entirely. This provides direct control of the laser
diode bias during setup and calibration. In either case, the
V
APCCFG bits determine the DACs response to higher or
lower numeric values.
22
BIAS
Figure 4. MIC3001 APC and Modulation Control
DAC setting is reported in the APCDAC register. The
Figure 5. Programmable Feedback Resistor
BIAS
DAC. When APC is off, the V
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Block Diagram
BIAS
register, bypassing the look-
or [phone]
M9999-082404-A
BIAS
MIC3001
DAC may