Data Sheet

21

V2.1, 2007-06-20

TLE7188F

Shunt Signal Conditioning

5.3

Shunt Signal Conditioning

The TLE7188F incorporates three fast and precise operational amplifiers for conditioning and amplification of the

shunt signals sensed in the three phases. Additionally, one reference bias buffer is integrated to provide an

adjustable bias reference for the three OpAmps. The voltage divider on the VRI pin should be less than 50 kOhm,

the filtering capacitor less than 1.2 µF - if needed at all. The gain of the OpAmps is adjustable by external resistors

within a range of 5 to 15.

When V(ISP) = V(ISN), VO provides the reference voltage VRO. VRO is normally half of the regulated voltage

provided from an external voltage regulator for the ADC used to read the current sense signal. The additional

buffer allows bi-directional current sensing and permits the adaptation of the reference bias to different µC I/O

voltages. The reference buffer assures a stable reference voltage even in the high frequency range.

The reference bias buffer is used for all of the OpAmps. The OpAmps of the TLE7188F demonstrate low offset

voltages and very little drift over temperature, thus allowing accurate phase current measurements.

Figure 4

Shunt Signal Conditioning Block Diagram and Over Current Limitation

Over current warning see Chapter 5.2.2.

VRI

VRO

ISP1

ISN1

-

+

Shunt 1

Rfb

Rfb

Rs

Rs

VTHOC

VO1

blanking

time

1.5µs

to Error

logic

Over

current

Bias

Reference

I-DC Link

OpAmp1

OC

Comp

5V

5V

ISP2

ISN2

Shunt 2

I-DC Link

OpAmp2

blanking

time

1.5µs

Over

current

OC

Comp

VO2

ISP3

ISN3

Shunt 3

I-DC Link

OpAmp3

blanking

time

1.5µs

Over

current

OC

Comp

VO3

Rfb

Rfb

Rs

Rs

Rs

Rs

Adjustable over current limit

(VTHOC = 0

OC disabled)

to ADCs

TLE7188F

Adjustable

bias

reference

V

IN1

R

VRI

R

VRI

C

VRI

C

R