CS5462 datasheet(12/18 Pages) CIRRUS

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CS5462

4. FUNCTIONAL DESCRIPTION

4.1

Programmable Gain Amplifier (PGA)

The CS5462 is equipped with a PGA on the current

channel. While the voltage channel is always set to

a 10x differential input voltage range (50 0mVP-P),

the current channel can be set to one of two differ-

ent input ranges. The maximum differential voltage

range on the current channel can be set to 10x

(500 mVP-P) and 50x (100 mVP-P).

The gain setting of the current channel’s PGA and

also the high pass filter option are selected by con-

necting the IGAIN pin to one of seven Program Se-

lect output pins. For all applications the IGAIN pin

must be tied to one and only one Program Select

pins. Figure 2 below shows the different options

that can be selected at startup. These seven differ-

ent options allow the CS5462’s PGA to be set up in

either 10x or 50x mode and enable or disable the

high pass filters in either of the voltage or the cur-

rent channels.

During Startup the CS5462 will scan the IGAIN in-

put pin and determine which Program Select out-

put it is connected to and then set the PGA and

HPF’s accordingly.

4.2

Pulse-Rate Output

E1 and E2 pins provide a simple interface from

which signed energy can be accumulated. E1 and

E2 can be set to either stepper motor mode or me-

chanical counter mode. The connectivity of the

FREQ pin determines the pulse output mode and

also the maximum frequency for E1 and E2. Figure

3 below describes the options for E1 and E2.

For all applications FREQ must be connected to

one and only one of the Program Selects outputs

(P1 - P7). The frequency setting chosen using the

above table is equal to the set pulse rate frequency

if and only if a full-scale signal is applied to each

channel. As the input signal decreases the pulse

rate and pulse width will decrease by a percentage

equal to the product of the percentages of full-

scale inputs across each channel. For example, if

if FREQ is connected to P5, the maximum pulse

output rate is 4 Hz. Assuming 500 mV is selected

as full scale on each channel, 400 mV is measured

on current and voltage channels. 400 mV is 80% of

full scale. Since power is the product of current and

voltage the pulse outputs will be 80% * 80% = 64%

of full scale. Since 4Hz is the set full scale output

rate, pulses should appear on E1 and E2 at a

64% * 4 Hz = 2.56 Hz rate.

4.2.1

Stepper Motor Format.

In stepper motor mode the CS5462 produces alter-

nating pulses on E1 and E2. This pulse format is

designed to directly drive a stepper motor. Each

pin produces active-low pulses with frequency de-

pendent pulse widths. The figure below shows the

frequency and corresponding pulse width for each

option.

IGAIN

500mV

P-P

10x

100mV

P-P

50x

500mV

P-P

10x

100mV

P-P

50x

500mV

P-P

10x

100mV

P-P

50x

500mV

P-P

10x

no hpf

hpf both

hpf Ich

hpf Vch

Figure 2. PGA Settings

FREQ

0.25 Hz / Step

0.5 Hz / Step

1 Hz / Step

2 Hz / Step

4 Hz / Step

2 Hz / mech cnt

16 Hz / mech cnt

Figure 3. Pulse Output Settings

0.2 5 Hz

0.5 Hz

250 m s

P ulse W idth

Frequency

FREQ

connecte d to:

1 Hz

2 Hz

250 m s

4 Hz

125 m s

pulse width

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