MFC2000 datasheet(136/426 Pages) ETC

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MFC2000 Multifunctional Peripheral Controller 2000

Hardware Description

5-10

Conexant

100723A

5.1.7

POWER DOWN DETECTION

The power down detection circuit was only external for the MFC1000 chip. The PWRDWNn input signal to

MFC1000 is the output of the external power down detection circuit. The MFC2000 has two internal power down

detectors. The PWRDWNn is configurable either from internal power down detectors or from external power down

detector. The EXT_PWRDWN_SELn is used to select internal or external power down detector. The external

power down detector is selected when the EXT_PWRDWN_SELn pin is low. If the internal power detectors are

selected, the combination of two power down detector can be further selected through the internal register. The

purpose of having internal power down detector is to automatically generate reset after voltage drop on the power

supply without having external power down detector. The power supply voltage is compared with internally

generated threshold voltages. In order to prevent erratic resets, the comparator is designed with hysteresis

feature. During the power up, the output of the comparator will be low when the power supply voltage is at least

Von. Then as the voltage continues to increase and becomes larger than Von, the comparator output will be high. If

at any time, the supply voltage drops below the threshold voltage level of Voff, then the comparator output will be

low.

POWER1

pwr_down1

POWER2

Voltage Detector

pwr_down2

Reference

Voltage

Figure 5-5. Internal Power Detection

ADGA

Input Voltage (V)

hys

off

ADVA

[Sia2k-comp-tf.vcd]

Figure 5-6. Figure Caption Required

MFC2000 Datasheet(PDF) 136 Page - List of Unclassifed Manufacturers