CS5460 datasheet(27/34 Pages) CIRRUS

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CS5460

DS279PP5

gy register is read every second. As a result, the

WDT will not time out. Other applications, that

want to use the watchdog timer, will need to ensure

that the Energy register is read at least once in ev-

ery 5 second span.

5.2 Oscillator Characteristics

XIN and XOUT are the input and output, respec-

tively, of an inverting amplifier to provide oscilla-

tion and can be configured as an on-chip oscillator,

as shown in Figure 11. The oscillator circuit is de-

signed to work with a quartz crystal or a ceramic

resonator. To reduce circuit cost two load capaci-

tors C1 are integrated in the device, one between

XIN and DGND, one between XOUT and DGND.

Lead lengths should be minimized to reduce stray

capacitance. With these load capacitors the oscilla-

tor circuit is capable of oscillation up to 20 MHz.

To drive the device from an external clock source,

XOUT should be left unconnected while XIN is

driven by the external circuitry. There is an ampli-

fier between XIN and the digital section which pro-

vides CMOS level signals. This amplifier works

with sinusoidal inputs so there are no problems

with slow edge times.

The CS5460 can be driven by a clock ranging from

2.5 to 20 MHz Table 2 shows the clock divide value

K (default = 1) that the CS5460 needs to be pro-

grammed with for normal operation.

5.3 Analog Inputs

The CS5460 accommodates a full scale range of

150 mVRMS on both input channels. System cali-

bration can be used to increase or decrease the full

scale span of the converter as long as the calibra-

tion register values stay within the limits specified.

See the Calibration section for more details.

The current input channel has an input range of 30

mVRMS when the internal x50 gain stage is en-

abled. This signal range is designed to handle low

level signals from a shunt sensor.

CLK (min)

MHz

CLK (max)

MHz

12.5

410

Table 3. CPU Clock (and K) Restrictions

Oscillator

Circuit

DGND

XIN

XOUT

C1 = 22 pF

Figure 11. Oscillator Connection

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