CS5460A-BS View Datasheet(PDF) - Cirrus Logic

Part Name

Description

MFG CO.

CS5460A-BS

Single Phase, Bi-directional Power/Energy IC

Cirrus Logic 

CS5460A

performed on each individual power meter, during

final calibration/test of the meter.

3.14 Protection Against High-voltage

and/or High-current Surges

In many power distribution systems, it is very likely

that the power lines will occasionally carry brief but

large transient spikes of voltage/current. Two com-

mon sources of such high-energy disturbances are

1) a surge in the line during a lightning storm, or 2)

a surge that is caused when a very inductive or ca-

pacitive load on the power line is suddenly turned

on (“inductive kick”). In these situations, the input

protection resistors and corresponding input filter

capacitors (discussed in the previous sections)

may not be sufficient to protect the CS5460A from

such high-frequency voltage/current surges. The

surges may still be strong enough to cause perma-

nent damage to the CS5460A. Because of this, the

designer should consider adding certain additional

components within the voltage/current channel in-

put circuitry, which can help to protect the

CS5460A from being permanently damaged by the

surges.

Referring to Figure 20, the addition of capacitors

C1 and C2 can help to further attenuate these

high-frequency power surges, which can greatly

decrease the chances that the CS5460A will be

damaged. Typical values for C1 and C2 may be on

the order of 10 pF, although the exact value is re-

lated to the reactive and resistive properties of the

voltage and current sensor devices. In addition, di-

odes D1 - D4 can help to quickly clamp a high volt-

age surge voltage presented across the

voltage/current inputs, before such a surge can

damage the CS5460A. An example of a suitable

diode part number for this application is BAV199,

which has the ability to turn on very quickly (very

small turn-on time). A fuse could potentially serve

this purpose as well (not shown). R3 and R4 can

provide protection on the “-” sides of the two input

pairs. Set R3 = R1 and R4 = R5. Finally, placing

50 Ω resistors in series with the VA+ and VD+ pins

is another technique that has sometimes proven to

be effective in protecting the CS5460A from such

high-level, high-frequency voltage/current surges.

However, these 50 Ω resistors may not be neces-

sary if the protection on the analog input channels

is sufficient, and this is not the most attractive so-

10 kΩ

5 kΩ

N

L

500 Ω

500 Ω

10 Ω

120 Vrms

470 nF

100 µF

5.1 Volt

0.1 µF

50

0.1 µF

50

R2

R1

C1

C2

To Service

L1

D1

D2

R3

L2

L3

R4

D3

D4

RSHUNT

R5

L4

C3

C5

C6

C8

14

3

VA+

VD+

CS5460A

MODE 8

9 VIN+

PFMON 17

CPUCLK 2

XOUT 1

C4

NC

NC

4.069 MHz

10 VIN-

15 IIN-

XIN 24

INT 19

C7

16 IIN+

12 VREFIN

11 VREFOUT

SDO 7

SCLK 23

CS 6

SDI 5

RESET

EDIR

EOUT

20

22

21

0.1 µF

VA-

13

DGND

4

RL

Input protection for single-ended input configurations, using resistive

divider and current shunt resistor.

Note that the digital interface is isolated using opto-isolators.

For Input Surge

Protection

To reduce

EMI susceptibility

20 k 20 k

+5 V

10 k 10 k

1k

1k

+5 V

1k

1k

1k

1k

Figure 20. Input Protection for Single-Ended Input Configurations

+5 V

47 k 47 k

SCLK

SDO

CS

INT

SDI

RST

GND

DS487F4

37

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