SAP5SD-B-G1-R datasheet(28/63 Pages) ETC2

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SAP5S / SAP51

Universal Actuator-Sensor Interface IC

Data Sheet

July 17, 2012

the prior written consent of the copyright owner. The information furnished in this publication is PRELIMINARY and subject to

changes without notice.

28 of 62

Detailed Functional Description

4.1. Power Supply

The power supply block provides a sensor supply, which is inductively decoupled from the AS-i bus voltage, at

pin UOUT. The decoupling is realized by an Electronic Inductor circuit, which basically consists of a current

source and a controlling low pass. The time constant of the low pass that has influence to the resulting input

impedance at pin UIN, can be adjusted by an external capacitor at pin CDC.

A second function of the power supply block is to generate a regulated 5V supply for operation of the internal

logic and some analog circuitry. The voltage is provided at pin U5R an can be used to supply external circuitry

as well, as long as the current requirements stay within in the specified limits (Table 2 at page 10). Because

the 5V supply is generated out of the decoupled sensor supply at UOUT, the current drawn at U5R has to be

subtracted from the total available load current at UOUT.

The power supply dissipates the major amount of power:

Ptot = VDrop* (IUOUT + I5V) + (VUOUT-5V) * I5V

In total, the power dissipation shall not exceed the specified values of chapter 1.1.

To cope with fast internal and external load changes (spikes) external capacitors at UOUT and U5R are

required. The LTGN pin defines the ground reference voltage for both UOUT and U5R.

4.1.1.

Voltage Output Pins UOUT and U5R

Table 12: Properties of voltage output pins UOUT and U5R

Symbol Parameter

Min

Max

Unit

Note

VUIN

Positive supply voltage for IC

operation

VDROP

Voltage drop from pin LTGP to pin

UOUT

5.2

7.8

VUIN > 22V

VUOUT

UOUT output supply voltage

VUIN- VDROPmax

VUIN- VDROPmin

IUOUTmax

VUOUTp

UOUT output voltage pulse deviation

1.5

tUOUTp

UOUT output voltage pulse deviation

width

VU5R

5V supply voltage

4.75

5.25

IUOUT

UOUT output supply current

IU5R = 0

Uin>24V

I5V

U5R output supply current

Total output current IUOUT + I5V

CBUOUT

Blocking capacitance at UOUT

470

µF

CB5V

Blocking capacitance at U5R

100

1 Parameter copied from Table 2 at page 10

2 The actual voltage drop increases with increasing load current at Uout

3 C

UOUT = 10µF, output current switches from 0 to IUOUTmax and vice versa

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