PLL702-06

Clock Generator for Printer Applications

47745 Fremont Blvd., Fremont, California 94538 Tel (510) 492-0990 Fax (510) 492-0991

www.phaselink.com

Rev 10/26/05 Page 4

Note: when the output load presents a low impedance in comparison to the internal pull-up resistor, the internal pull-up resistor

may not be sufficient to pull the input up to a logical “one”, and an external pull-up resistor may be required.

For bi-directional inputs, the external loading resistor between the pin and GND has to be sufficiently small (compared to the

internal pull-up resistor) so that the pin voltage be pulled below 0.8V (logical “zero”). In order to avoid loading effects when the pin

serves as output, the value of the external pull-down resistor should however be kept as large as possible. In general, it is

recommended to use an external resistor of around one sixth to one quarter of the internal pull-up resistor (see Application

Diagram).

VDD Power Up Ramp Requirements:

At startup, the chip reads a lot of settings for operation according to the application’s requirements. Since reading the settings is

done only at startup and then frozen for the time of operation, it is important that the power-up environment is somewhat

controlled to facilitate proper reading of the settings. The important VDD pins are VDDA (Pin3) and VDDD (Pin4) and they should

apply to the following two-startup requirements:

•

VDDD should be equally fast or slower than VDDA. VDDD performs a chip reset when VDD has reached a certain level and

VDDA should have reached at least up to the same level as well to properly process the reset.

•

The VDD Power Up Ramp of VDDD and VDDA should pass through the section 1.8V to 2.5V no faster than 100µs and with

a continuously increasing slope. In this section the tri-level select inputs are read.

•

After VDD Power off, VDD should be allowed to go to 0V and stay there for at least 1ms before a new VDD Power on. It is

important that proper preconditions exist at every startup. Remaining charges in the chip or in circuit filter capacitors may

interfere with the preconditions so it is important that VDD has been at 0V for some time before each startup.

GND (0V)

3.3V

No

limit

Min 1ms

VDD off

VDD on

2.97V

2.5V

2.2V

Min 1s

Reset enable

Reset disable

1.8

V

>100us