AK2572 Datasheet, PDF(30/50 Page) Asahi Kasei Microsystems – APC for Burst Mode Applicable Direct Modulation Laser Diode

English

English German Russian Spanish Italian Polish Chinese Japanese Korean French Portuguese	Language :

AK2572 Datasheet, PDF (30/50 Pages) Asahi Kasei Microsystems – APC for Burst Mode Applicable Direct Modulation Laser Diode

◁

ASAHI KASEI

[AK2572]

8. Start-Up Setting in SFP Support Mode

8.1 TXFAULT Detection at Power-Up and after Release from Shutdown

8.1.1 OPTALM

In SFP support mode setting (RE_SFP_SETï¼â0â), a mask time can be programmed for TXFAULT detection by

OPTALM during the shutdown release so that a time constant delay derived from the external Rpd and Cpd for

detection of the averaged monitor-PD current at the turning-on of LD must be taken into consideration. Block

diagram in Figure 8-1, and pre-settable mask time relation in Table 8-1 are shown.

In the AK2572, the delay time can be shortened by accelerated start-up setting which is made by initial value

setting function of R_APC_FB and so on.

But when OPTALM is selected as one of the TXFAULT target ALMs, and a mask time is set to be shortened, be

noted that LD optical power will not reach the expected level within the mask time and it may be shutdown

through OPTALM detection to TXFAULT control sequence if initial set value of APC_FF or APC_FB is far off.

Figure 8-1 OPTALM Detection Block Diagram

PDGAIN setting

Monitor

(RE_PDGAIN)

PDIN

vpd

PDGAIN

Cpd

Rpd

vapc_ref

A time constant delay at

shutdown release derived

from the external Rpd and

Cpd must be taken into

consideration

APC target

(R_APC_TRGT)

DAC_APC

APC_

COMP

DIGITAL

FILTER

APC Feedback value (R_APC_FB)

OPALM setting

(R_OPTALM)

OPTALM

_COMP

ATT

OPTALM threshold

(optalm_ref)

TXFAULT

CONTROL

Table 8-1 Time to Valid TXFAULT Detection by OPTALM

RE_

RE_TIMER RE_APC_ RE_APC Mask time for TXFAULT

SFP_SET _OPTALM INIT_SET _FF_SET detection by OPTALM

160 ms [Typ.]

00, 01, 10

160 ms [Typ.]

2 ms [Typ.]

0 ms

Note

Accelerated start-up setting

Non-support SFP

8.1.2 EXTALM1, EXTALM2

In SFP support mode setting (RE_SFP_SETï¼â0â), a mask time can be set for TXFAULT detection by

EXTALM1 and EXTALM2 at the shutdown release.

In Table 8-2, a delay time relation to be set is shown.

Table 8-2 Time to Valid TXFAULT Detection by EXTALM1, EXTALM2

RE_SFP_SET

RE_TIMER_EXTALM1

RE_TIMER_EXTALM2

Mask time for TXFAULT detection

by EXTALM1, EXTALM 2

0 ms

2 ms [Typ.]

0 ms

Note

Non-support SFP

-30-

< MS0290-E-01>

2004/8

▷