Datasheet
18 _____________________________________________________________________________________
MAX3946
1Gbps to 11.3Gbps, SFP+ Laser Driver
with Laser Impedance Mismatch Tolerance
Transmitter Status Register 1 (TXSTAT1)
Bit 7: FST[7]. When the V
CCT
supply voltage is below 2.3V, the POR circuitry reports a fault. Once the V
CCT
supply
voltage is above 2.75V, the POR resets all registers to their default values and the fault is cleared.
Bit 6: FST[6]. When the voltage at BMON is above V
CC
- 0.5V, a SOFT FAULT is reported.
Bit 4: FST[4]. When the voltage at BMAX goes above 1.3V, a HARD FAULT is reported.
Bit 3: FST[3]. When the common-mode voltage at V
TOUTQ
goes below V
CC
- 1.3V, a SOFT FAULT is reported.
Bit 2: FST[2]. When the voltage at V
TOUTQ
goes below V
CC
- 0.8V, a HARD FAULT is reported.
Bit 1: FST[1]. When the BIAS voltage goes below 0.44V, a HARD FAULT is reported.
Bit 0: TX_FAULT. Copy of a FAULT signal in FST[7:6] and FST[4:1]. A POR resets the FST bits to 0.
Transmitter Status Register 2 (TXSTAT2)
Bit 3: IMODERR. Any attempt to modify SET_IMOD[8:1] above IMODMAX[7:0] flags a warning at IMODERR. (See the
Programming Modulation Current section.)
Bit 2: IBIASERR. Any attempt to modify SET_IBIAS[8:1] above IBIASMAX[7:0] flags a warning at IBIASERR. (See the
Programming Bias Current section.)
Bit 1: TXED. This indicates the absence of an AC signal at the transmit input.
Bias Current Setting Register (SET_IBIAS)
Bits 7 to 0: SET_IBIAS[8:1]. The bias current DAC is controlled by a total of 9 bits. The SET_IBIAS[8:1] bits are used
to set the bias current with even denominations from 0 to 510 bits. The LSB (SET_IBIAS[0]) is controlled by the BIASINC
register and is used to set the odd denominations in the SET_IBIAS[8:0]. Any direct write to SET_IBIAS[8:1] resets the
LSB.
Bit #
7
(STICKY)
6
(STICKY)
5
(STICKY)
4
(STICKY)
3
(STICKY)
2
(STICKY)
1
(STICKY)
0
(STICKY)
ADDRESS
Name FST[7] FST[6] X FST[4] FST[3] FST[2] FST[1] TX_FAULT
H0x06
Default Value X X X X X X X X
Bit #
7 6 5 4
3
(STICKY)
2
(STICKY)
1
(STICKY)
0
(STICKY)
ADDRESS
Name X X X X IMODERR IBIASERR TXED X
H0x07
Default Value X X X X X X X X
Bit #
7 6 5 4 3 2 1 0 ADDRESS
Name
SET_IBIAS
[8] (MSB)
SET_IBIAS
[7]
SET_IBIAS
[6]
SET_IBIAS
[5]
SET_IBIAS
[4]
SET_IBIAS
[3]
SET_IBIAS
[2]
SET_IBIAS
[1]
H0x08
Default Value 0 0 0 0 0 0 0 1