ds1861 Maxim Integrated Products, Inc., ds1861 Datasheet - Page 19

• Manufacturer Part Number: ds1861
• Description: Ds1861 Full Laser Control With Fault Management
• Manufacturer: Maxim Integrated Products, Inc.

Name of Row
• Name of Byte...<Write Access><Volatility><Power-
Up/Factory Default Value>
Write Access: W is write-only access, R is read-only
access, and R/W is read/write access. A password may
be required for write access on R/W registers. See the
memory map for complete access code descriptions.
Volatility: V is volatile (SRAM), NV is nonvolatile (EEPROM).
Power-Up/Factory Default Value: For SRAM registers,
this value is always the power-up value. For EEPROM
registers, this is the factory default value. These can be
permanently modified by entering the password and
writing the register. N/A is used for hardware-depen-
dent values, such as alarm flags.
Password Entry
• Status <R><V><N/A, depends on power-up condi-
tion>
Detailed Register Description Conventions
0. Name of bit 0.....Bit 0 Description
1. Name of bit 1.....Bit 1 Description
2 to 7. Bit names.....Bit 2 to 7 Descriptions
0. HBIAS Alarm.....High Bias-Current Alarm. This
1. LTXP Alarm.....Low Transmitted Power Alarm.
2. HTXP Alarm....High Transmitted Power Alarm.
3. POA....Analog Power-On Reset Alarm (V
4. HBIAS Shutdown....This flag goes high when a
flag is high when I
Threshold. This flag is updated every 4µs or
16µs depending on the state of the convergence
algorithm. Programming HBIAS threshold byte to
zero disables the HBIAS Alarm.
This flag is high when the I
below the value set by the LTXP threshold. This
flag is updated every 16µs. Programming LTXP
threshold to zero disables this flag. This flag willl
be high when TX-D = 1 unless the alarm has
been disabled.
This flag is high when the I
above the value set by the HTXP threshold. This
flag is updated every 16µs. Programming HTXP
Threshold to zero disables this flag.
Power Good). This flag is set when V
HBIAS safety fault is generated and HBIAS
Enable is high. HBIAS Shutdown goes low with
POA or a falling edge of the TX-D pin, providing
the safety fault is no longer present.
Full Laser Control with Fault Management
BIASSET
BMD
BMD
____________________________________________________________________
≥ HBIAS Alarm
current drops
current rises
CC
< V
POA
CC
.
• PWE High & Low....<R/W><V><FFFFh> Until the cor-
rect 32-bit password is written to PWE, the PWE bytes
are the only locations that can be written. PWE should
be written to a value other than the password once the
device’s configuration has been updated to prevent the
password from being read from PWE. After a power
cycle these locations will each be reset to FFFFh.
APC Config
• APC....<R/W><NV><00h> Sets the desired value of
the feedback current into the I
determine the input GAIN value according to this table:
The remaining 5 LSBs determine the I
point (I
I
If values greater than 10011111b (9Fh) are pro-
grammed into the APC register, the DS1861 will clamp
I
was set to 10011111b.
• ER (N)....<R/W><NV><1Ch> Sets the gain (N) on the
measured excitation current used to generate I
This sets the extinction ratio of the system. Higher N
values increase the excitation ratio. The MSB of this
register (RSEL) is a flag that selects a high (RSEL = 1)
or low (RSEL = 0) range for N. The 7 LSBs of the regis-
ter determine the actual N code. The value of N can be
calculated by the following equation:
BMD
SET
5. LTXP Shutdown....This flag goes high when a
6. HTXP Shutdown....This flag goes high when a
7. Shutdown Flag....This flag is high when any of
to its maximum value, equivalent to if the register
current setpoint with the gain is then given by:
LTXP safety fault is generated and LTXP Enable
is high. LTXP Shutdown goes low with POA or a
falling edge of TX-D, providing the safety fault is
no longer present.
HTXP safety fault is generated and HTXP Enable
is high. HTXP Shutdown goes low with POA or a
falling edge of TX-D, providing the safety fault is
no longer present.
the three latched safety faults are high (HBIAS
Shutdown, LTXP Shutdown, or HTXP Shutdown),
and it remains high after the individual flag’s are
reset until fault reset time has elapsed.
SET
I
SET
APC<7:5>
) assuming a GAIN of 1. The formula for the
000
001
010
011
1xx
= 1.525µA GAIN (APC<4:0> + 32)
BMD
pin. The 3 MSB’s
BMD
GAIN
16
1
2
4
8
current set-
MODSET
19
.