DS1863 Просмотр технического описания (PDF) - Maxim Integrated

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DS1863

Burst-Mode PON Controller With Integrated Monitoring

Maxim Integrated 

Burst-Mode PON Controller

With Integrated Monitoring

APC LOOP/QUICK TRIP SAMPLE TIMING

BEN

tFIRST

BIAS DAC

CODE

QUICK-TRIP

SAMPLE TIMES

LAST BURST'S

BIAS SAMPLE

BIAS

SAMPLE

tREP

BIAS

SAMPLE

BIAS

SAMPLE

BIAS

SAMPLE

BIAS

SAMPLE

BIAS

SAMPLE

BIAS

SAMPLE

H/LTXP

HBIAS

SAMPLE SAMPLE

Figure 3. APC/Quick-Trip Alarm Sample Timing.

Monitors And Fault Detection

Monitors

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 And Alarms

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

quick-trip alarm levels and masks are programmable

through the I2C interface.

Five ADC Monitors And Alarms

The ADC monitors five channels that measure tempera-

ture (internal temp sensor), VCC, MON1, MON2, and

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 I2C bus. This allows customers with spec-

ified ADC ranges to calibrate the ADC full scale to a

factor of 1/2n of their specified range to measure small

signals. The DS1863 can then right shift the results by n

bits to maintain the bit weight of their specification.

ADC Default Monitor Full Scale Ranges

SIGNAL (UNITS)

Temperature (oC)

VCC (V)

MON1, MON2,

MON3 (V)

+ FS

SIGNAL

127.996

6.5528

2.4997

+ FS

HEX

7FFF

FFF8

FFF8

- FS

SIGNAL

-128

0V

0V

- FS

HEX

8000

0000

0000

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

I2C interface, as are the masking registers that can be

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