CPC5712UTR データシートの表示（PDF） - IXYS CORPORATION

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CPC5712UTR

Voltage Monitor with Detectors

IXYS CORPORATION 

INTEGRATED CIRCUITS DIVISION

3.3.2 Verify Resistor Selection

Once the resistor values are chosen it is necessary to

back calculate the nominal detector thresholds.

To do this the following equations are provided for two

variables:

R = RIN1 + RIN2 + RDIFF

RREF = R1 + R2 + R3 + R4 + R5

where R is the sum of the resistive interface network

and RREF is the sum of the resistor divider network on

the reference voltage output.

The following values are also needed to perform the

threshold calculations. They are:

• VREF = 1.5V

• RIN1 = RIN2 = 2 x 10M = 20M

• RDIFF = 806k

• G=2.5 (Single ended gain of input amplifier)

which gives:

• R = 40.806M and

• RREF = 270.1k

The threshold equations are:

1.

VL1 = -G--V----R--R-E---DF----I--F--R-F-------R---R-R---1E---F-

2.

VH1 = V----R---GE---F------R--R--D---I--F---F---R----R1----R-+--E---RF----2---

3.

VL2 = V----R---E---F----G----R----R----D----I-R-F---F1-----+--R---R-R---2E---F-+-----R----3----

4.

VH2 = V----R---E---F--------R--G---------R--R--D--1-I--F--+-F----R---R-2---R-+--E---RF----3-----+----R----4----

CPC5712

Using the selected standard 1% resistor values, and

back calculating to the threshold voltages produces

these results:

• VL1 = 3.00280V

• VH1 = 5.00467V

• VL2 = 11.9662V

• VH2 = 14.9690V

As can be seen, the error from using standard value

resistors is less than 0.1% for VL1 and VH1 and is less

than 0.3% for VL2 and VH2.

3.4 High Voltage Detection Designs

Designs that require higher detection levels greater

than approximately 17V will necessitate a different

voltage divider ratio to accommodate the operational

range of the CPC5712’s internal circuitry. Changes to

the input resistor divider network are restricted to the

high impedance resistors from the tip and ring leads to

the IN+ and IN- inputs. Changing the differential input

resistor value from 806k is not recommended as this

will introduce offset errors. The degree of offset error

caused by changing this component’s value is not

measured and therefore not calculable.

The design procedure for higher voltage detect levels

is the same as presented above. Remember to begin

with the equations shown in Section 2.5 “Detector

Threshold Operation” on page 6 and use the

updated value for the “A” term based on the new input

resistor values.

R02

www.ixysic.com

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