Glitch Filter

A digital glitch filter provides debouncing and filtering of

the noisy sensor signals. The time constant of this filter

is selectable between 0 (i.e., no filtering), 25µs, 0.75ms,

and 3ms. The selection is achieved through pins DB0

and DB1. The filtered outputs of the comparators are pre-

sented to the logic output pins, OP1–OP8.

To provide the digital glitch filter, the device checks that an

input is stable for at least three clock cycles. The duration

of a clock cycle is 1/3 of the selected debounce time. If the

input is not stable for at least three clock cycles, the input

change is not sent to the internal shift register.

Temperature Monitoring

The internal junction temperature of the IC is constantly

monitored and an alarm is raised, by asserting the FAULT

Supply Voltage Monitoring

A primary supply voltage-monitor circuit constantly moni-

tors the field-supply voltage. If this voltage falls below a

the FAULT and UVFAULT pins, indicating to the microcon-

troller that the part is experiencing a fault condition and

the data is not to be trusted. Once the field-supply voltage

UVFAULT pins are released.

Powering the Device Through the 5VOUT Pin

The device can alternatively be powered using a 5V

supply connected to the 5VOUT pin. In this case, a

24V supply is no longer needed and the VCC24V

supply must be kept unconnected. (see Figure 1)

In this configuration, the device will always indicate

a UVFAULT and the FAULT pin will always be active

(pulled low). Faults due to the supply voltage monitoring

and temperature monitoring will not be available.

This configuration has lower power consumption and

heat dissipation since the on-chip 5V voltage regulator

is disabled.

JUMPERS TO 5V

AND GND

Figure 1: Basic Application Powered Through 5VOUT

MAX31915

Industrial, Octal, Digital Input Translator

www.maximintegrated.com

Maxim Integrated │ 10