UPD17708 datasheet(23/356 Pages) NEC

23 / 356 page

µPD17704, 17705, 17707, 17708, 17709

1.4 Cautions on Using CE, INT0 through INT4, and RESET Pins

The CE, INT0 through INT4, and RESET pins have a function to set a test mode in which the internal

operations of the

µPD17709 are tested (IC test), in addition to the functions listed in 1.1 Pin Function List.

When a voltage exceeding VDD is applied to any of these pins, the device is set in the test mode. If a noise

exceeding VDD is superimposed during normal operation, therefore, the test mode is set by mistake, hindering

the normal operation.

Especially if the wiring length of pins is too long, noise is superimposed on these pins. In consequence,

the above problem occurs.

Therefore, keep the wiring length as short as possible to prevent noise from being superimposed.

superimposition of noise is unavoidable, connect an external component as illustrated below to suppress the

noise.

•

Connect a diode with low VF

•

Connect a capacitor between a pin and VDD.

between a pin and VDD.

1.5 Cautions on Using TEST Pin

When VDD is applied to the TEST pin, the device is set in the test mode. Therefore, be sure to keep the wiring

length of this pin as short as possible, and directly connect it to the GND pin.

If the wiring length between the TEST pin and GND pin is too long, or if external noise is superimposed on

the TEST pin, generating a potential difference between the TEST pin and GND pin, your program may not run

normally.

CE, INT0-INT4, RESET

VDD

CE, INT0-INT4, RESET

VDD

Diode with

low VF

VDD

GND TEST

Short

UPD17708 Datasheet(PDF) 23 Page - NEC