FT800 datasheet(31/55 Pages) FTDI

31 / 55 page

Document No.: FT_000792

FT800

Embedded Video Engine

Datasheet Version 1.1

Clearance No.: FTDI# 334

4.8.2 Internal Regulator and POR

The 1.2V internal regulator provides power to the core circuit. The regulator is disabled when

device is in POWERDOWN state. Power down is activated either by the SCU command write or

by holding down the PD_N pin for at least 5mS to allow the 1.2V decoupling capacitor to

discharge fully. The regulator is enabled only by releasing the PD_N pin. A 47kΩ resistor is

recommended to pull the PD_N pin up to VCCIO, together with a 100nF capacitor to ground in

order to delay the 1.2V regulator powering up after the VCC and VCCIO are stable.

The 1.2V internal regulator requires a compensation capacitor to be stable. A typical design

puts a 4.7uF capacitor with ESR >0.5Ω is required between VCC1V2 to GND pins. Do not

connect any load to this pin.

The 1.2V regulator will generate Power-On-Reset (POR) pulse when the output voltage rises

above the POR threshold. The POR will reset all the core digital circuits.

It is possible to use PD_N pin as an asynchronous hardware reset input. Drive PD_N low for at

least 5ms and then drive it high will reset the FT800 chip.

Figure 4-7 1.2V regulator

VCC

PD_N

VCC1V2

VCC

GND

VCCIO

Cin

10uF

100nF

1.2V

GND

Ccomp

4.7uF

47k

FT800

FT800 Datasheet(PDF) 31 Page - Future Technology Devices International Ltd.