TDC-GPX2 datasheet(40/77 Pages) AMSCO

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[v1-03] 2017-Dec-18

TDC-GPX2 − Detailed Description

Figure 41:

CMOS-LVDS

Termination of Differential LVDS Input Pin

Integrated termination is not provided. It is necessary to place

termination resistors on the PCB near to the input pins. The

default termination for LVDS signals is to have single 100Ω

resistors between the differential lines.

Connection of Unused LVDS Inputs

Any kind of unused LVDS inputs (e.g. STOP1 to STOP4, REFCLK,

RSTIDX, DISABLE, LCLKIN) have to be pulled up to VDD33 and

disabled by setting PIN_ENA to zero. Unused channels should

also be switched off with HIT_ENA_STOP1…4.

Figure 42:

Unused LVDS

Software Enable (HIT_ENA_STOP1…4)

Setting the configuration bits HIT_ENA_STOP1 to HIT_ENA_

STOP4 applies a software enable for stop channels 1 to 4.

Pin Enable (PIN_ENA_xxx)

The pin enable registers PIN_ENA_STOP1 to PIN_ENA_STOP4,

PIN_ENA_REFCLK, PIN_ENA_RSTIDX and PIN_ENA_DISABLE

activate the LVDS input or output drivers of the related pins.

Main purpose of PIN_ENA is cutting of current consumption of

unused differential LVDS buffer to nearly zero. But also with

CMOS_INPUTs the pin need to be activated. In case of the LVDS

output interface, PIN_ENA_STOP1 to PIN_ENA_STOP4 enable

also the according LVDS output drivers.

General Circuit

LVDS (CMOS_INPUT=0):

CMOS (CMOS_INPUT=1):

PIN_ENA

_STOP1

CMOS_IN

PUT

STOP1P

STOP1N

PIN_ENA_STOP1

STOP1P

STOP1N

STOP1

STOP1P

STOP1N

STOP1

TVDD33

PIN_ENA_STOPx=0

VDD33

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