MIC3003GFL datasheet(27/74 Pages) MICREL

27 / 74 page

Micrel, Inc.

MIC3003GFL

July 2010

M9999-072910-A

hbwhelp@micrel.com or (408) 955-1690

Figure 8. VMOD Configured as Voltage Output

with Gain

Power On and Laser Start-Up

When power is applied, the MIC3003 initializes its

internal registers and state machine. This process takes

tPOR, about 50ms. Following tPOR, analog-to-digital

conversions begin, serial communication is possible, and

the POR bit and data ready bits may be polled. The first

set of analog data will be available tCONV after tPOR.

MIC3003s are shipped from the factory with the output

enable bit, OE, set to zero, off. The power-up default

state, therefore, is APC off, VBIAS, VMOD, and SHDN

outputs disabled. VBIAS, VMOD, and SHDN will be floating

(high impedance) and the laser diode, if connected, will

be off. Once the device is incorporated into a transceiver

and properly configured, then the shutdown states of

SHDN, VBIAS, and VMOD will be determined by the state of

the APC configuration and OE bits. Tables 13, 14, and

15 illustrate the shutdown states of the various laser

control outputs versus the control bits.

Configuration Bits

Shutdown State

SPOL

SHDN

Don’t Care

Hi-Z

GND

VDD

Table 13. Shutdown State of SHDN vs.

Configuration Bits

VBIAS Shutdown State

INV

BIASREF

VBIAS

Don’t Care

Hi-Z

Don’t Care

GND

Don’t Care

VDD

Table 14. Shutdown State of VBIAS vs.

Configuration Bits

VMOD Shutdown State

MODREF

VMOD

Don’t Care

Hi-Z

GND

VDD

Table 15. Shutdown State of VMOD vs.

Configuration Bits

In order to facilitate hot-plugging, the laser diode is not

turned on until tINIT2 after Power-On. Following tINIT2, and

assuming TXDISABLE is not asserted, the DACs will be

loaded with their initial values. Since tCONV is much less

than tINIT2, the first set of analog data, including

temperature,

available

tINIT2. Temperature

compensation will be applied to the DAC values if

enabled. APC will begin if OE is asserted. (If the output

enable bit, OE, is not set, the VMOD, VBIAS, and SHDN

outputs will float indefinitely.) Figure 9 shows the power-

up timing of the MIC3003. If TXDISABLE is asserted at

power-up, the VMOD and VBIAS outputs will stay in their

shutdown states following MIC3003 initialization. A/D

conversions will begin, but the laser will remain off.

MIC3003GFL 데이터시트(PDF) 27 Page - Micrel Semiconductor

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