CTSR datasheet(8/11 Pages) LEM

8 / 11 page

Page 8/11

28January2014/version 7

LEM reserves the right to carry out modifications on its transducers, in order to improve them, without prior notice

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CTSR Series

Application information

Filtering, decoupling CTSR transducer

Supply voltage U

c (5 V):

The CTSR transducers have internal decoupling capacitors, but in the case of a power supply track on the application PCB having

a high impedance, it is advised to provide local decoupling, 100 nF or more, located close to the transducer.

Reference V

ref

Ripple present on the V

ref pin can be filtered with a low value of capacitance because of the internal 499 ohm series resistance.

The CTSR transducers have an internal capacitor of 22 nF between V

ref pin and Gnd pin and the maximum filter capacitance value

which could be added is 1 µF. Adding a larger decoupling capacitor will increase the activation delay of degauss.

Output V

out

The CTSR transducers have an internal low pass filter 470 ohm/22 nF; if a decoupling capacitor is added on V

out pin, the bandwidth

and the response time will be affected. In case of short circuit, the transducer CTSR can source or sink up to a maximum of 10

mA on its output V

out.

Using an external reference voltage

If the V

ref pin of the transducer is not used it could be either left unconnected or filtered according to the previous paragraph

“Reference V

ref”.

The V

ref pin has two modes Ref out and Ref In:

• In the Ref out mode the 2.5 V internal precision reference is used by the transducer as the reference point for bipolar

measurements; this internal reference is connected to the V

ref pin of the transducer through a 499 ohms resistor. It

tolerates sink or source currents up to ± 5 mA, but the 499 ohms resistor prevents this current to exceed these limits.

• In the Ref In mode, an external reference voltage is connected to the V

ref pin; this voltage is specified in the range 2.3

to 4 V and is directly used by the transducer as the reference point for measurements. The external reference voltage

ref must be able:

o either to source a typical current of

, the maximum value will be 3 mA when V

ref = 4 V.

o or to sink a typical current of

, the maximum value will be 0.4 mA when V

ref = 2.3 V.

The following graphs show how the measuring range of the transducer depends on the external reference voltage value V

ref

c = 5 V).

Upper limit: I

P= 500 mA

ref = 2.3 .. 2.625 V)

Upper limit: I

P= 850 mA

ref = 2.3 .. 2.52 V)

Upper limit: I

P= -250*Vref+1156.25

ref = 2.625 .. 4 V)

Upper limit: I

P= -403.88*Vref+1867.93 (Vref = 2.52 .. 4 V)

Lower limit: I

P= -250*Vref+93.75

ref= 2.3 .. 2.375 V)

Lower limit: I

P= -403.88*Vref+151.45

ref = 2.3 .. 2.48 V)

Lower limit: I

P= -500 mA

ref = 2.375 .. 4 V)

Lower limit: I

P= -850 mA

ref = 2.48 .. 4 V)

499

−

Vref

499

Vref

−

-1000

-800

-600

-400

-200

200

400

600

800

1000

Vref (V)

PRM 850 mA

-600

-400

-200

200

400

600

Vref (V)

PRM 500 mA

-1000

-800

-600

-400

-200

200

400

600

800

1000

Vref (V)

PRM 850 mA

-600

-400

-200

200

400

600

Vref (V)

PRM 500 mA

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