SAP5SD-B-G1-R datasheet(30/67 Pages) RENESAS

30 / 67 page

SAP51 / SAP5S Datasheet

January 28, 2016

5.6.

AS-i Transmitter

Figure 5.1

Basic Receiver Comparator Threshold Set-up Principles

First negative

pulse of the

AS-i telegram

VLSIGon

VLSIGon = (0.45 to 0.55) ∗ VSIG / 2

DC level

VSIG / 2

The IC determines the

amplitude of the first

negative pulse of the

AS-i telegram. This

amplitude is asserted

to be VSIG / 2.

The transmitter draws a modulated current between LTGP and LTGN to generate the communication signals. The

shape of the current corresponds to the integral of a sin

2-function. The transmitter comprises a current DAC and a

high-current driver. The driver requires a small bias current to flow. The bias current is ramped up slowly for a

specific time before the transmission starts so that any false voltage pulses on the AS-i line are avoided.

When the transmitter is turned on, the receiver is turned off to reduce the power consumption. The SAP5 includes

a Clock Watchdog that becomes activated once the clock signal is stopped for approximately 100µs to 150µs so

that the transmitter is prevented from being permanently switched on in case the clock signal is missing.

Table 5.8

Transmitter Current Amplitude

PARAMETER

SYMBOL

MIN

MAX

UNIT

Modulated transmitter peak current swing (between LTGP and LTGN)

ISIG

mAP

5.7.

Parameter Port and PSTBn

The parameter port is always configured for continuous bi-directional operation. However, if IO_Code=7HEX (see

Table 5.14), the parameter ports will return to high impedance state immediately after a WPAR request because

they act as data input ports or safety data ports for a subsequent DEXG master call.

Every pin contains an NMOS open-drain output driver plus a high-voltage, high-impedance digital input stage.

Received parameter output data is stored in the Parameter Output Register and subsequently forwarded to the

open-drain output drivers. A specific time (tPI-latch) after new output data has arrived at the port, the corresponding

inputs are sampled. Due to the open-drain of the output driver, the input value results from a wired AND

combination of the parameter output value and such signals driven to the port by external sources.

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