ds1863 Maxim Integrated Products, Inc., ds1863 Datasheet - Page 11

• Manufacturer Part Number: ds1863
• Description: Ds1863 Burst-mode Pon Controller With Integrated Monitoring
• Manufacturer: Maxim Integrated Products, Inc.

Monitoring functions on the DS1863 include four quick-
trip comparators and five ADC channels
This monitoring combined with the interrupt masks
determines when/if the DS1863 shuts down its outputs
and triggers the TX-F and FETG outputs. All of the mon-
itoring levels and interrupt masks are user programma-
ble with the exception of POA, which trips at a fixed
range and is non-maskable for safety reasons.
Four quick-trip monitors are provided to detect potential
laser safety issues. These monitor
1) High Bias Current (HBIAS)
2) Low Transmit Power (LTXP)
3) High Transmit Power (HTXP)
4) Max Output Current (MAX IBIAS)
The high and low transmit power quick-trip registers
(HTXP and LTXP) set the thresholds used to compare
against the BMD voltage to determine if the transmit
power is within specification. The HBIAS quick-trip
compares the MON1 input (generally from the
MAX3643 bias monitor output) against its threshold set-
ting to determine if the present bias current is above
specification. The Max Bias quick-trip is a digital com-
parison that determines if the Bias Output code indi-
cates the bias current is above specification. The bias
current will not be allowed to exceed the value set in
this register. When the DS1863 detects the bias is at
the limit it will set the BIAS MAX status bit and hold the
bias current at the MAX IBIAS level. The quick-trips are
routed to the TX-F and FETG outputs via interrupt
masks to allow combinations of these alarms to be
used to trigger these outputs. Any time FETG is trig-
gered the DS1863 will also disable its outputs. All the
Figure 3. APC/Quick-Trip Alarm Sample Timing.
APC LOOP/QUICK TRIP SAMPLE TIMING
SAMPLE TIMES
QUICK-TRIP
BIAS DAC
Four Quick-Trip Monitors And Alarms
CODE
BEN
Monitors And Fault Detection
LAST BURST'S
BIAS SAMPLE
t
FIRST
SAMPLE
BIAS
t
REP
____________________________________________________________________
SAMPLE
BIAS
Monitors
Burst-Mode PON Controller
With Integrated Monitoring
SAMPLE
BIAS
SAMPLE
BIAS
quick-trip alarm levels and masks are programmable
through the I
The ADC monitors five channels that measure tempera-
ture (internal temp sensor), V
MON3 using an analog multiplexer to measure them
round robin with a single ADC. Each channel has a
customer programmable full scale range and offset
value that will be factory programmed to default value
(see below). Additionally, MON1, MON2, and MON3
have the ability to right shift results by up to 7 bits
before the results are compared to alarm thresholds or
read over the I
ified ADC ranges to calibrate the ADC full scale to a
factor of 1/2
signals. The DS1863 can then right shift the results by n
bits to maintain the bit weight of their specification.
The ADC results (after right shifting, if used) are com-
pared to high alarm thresholds (to check if the results
exceeded this threshold), the low alarm thresholds (to
check if the ADC results are below this threshold) and
the warning threshold after each conversion (20 com-
parisons total), and the corresponding alarms are set
which can be used to trigger the TX-F or FETG outputs.
These ADC thresholds are user programmable via the
I
ADC Default Monitor Full Scale Ranges
2
Temperature (
V
MON1, MON2,
MON3 (V)
SIGNAL (UNITS)
C interface, as are the masking registers that can be
CC
(V)
SAMPLE
BIAS
n
2
C interface.
o
of their specified range to measure small
C)
2
C bus. This allows customers with spec-
SIGNAL
127.996
6.5528
2.4997
+ FS
SAMPLE
SAMPLE
Five ADC Monitors And Alarms
H/LTXP
BIAS
+ FS
7FFF
FFF8
FFF8
HEX
SAMPLE
CC
HBIAS
, MON1, MON2, and
SAMPLE
SIGNAL
BIAS
-128
- FS
0V
0V
8000
0000
0000
HEX
- FS
11