UPD75208 datasheet(39/62 Pages) NEC

39 / 62 page

µPD75208

(30 + 5.5 V)2

40 k

Ω

× 10 = 315 mW

× 2 V × 10 mA × 4 = 53 mW

*1. Calculation of total loss

Design so that the sum of the following three power consumption values for the

µPD75208CW/GF will be less

than the total loss PT (It is recommended to use the system with 80 % or less of the rating).

CPU loss

: Given as VDD (MAX.)

× IDD1 (MAX.)

Output pin loss

: There are normal output pin loss and display output pin loss. It is necessary

to add a loss derived from the flow of maximum current to each output pin.

Pull-down register loss : Power loss due to a pull-down resistor incorporated in the display output pin

by mask option.

Example

Suppose 4-LED output with 9SEG

× 11DIGIT, VDD = 5 V + 10 % and 4.19 MHz oscillation and let a maximum

of 3 mA, 15 mA and 10 mA flow to the segment pin, timing pin and LED output pin, respectively.

Further, let the voltage of fluorescent display tube (VLOAD voltage) be –30 V and normal voltage be small.

CPU loss : 5.5 V

× 9.0 mA = 49.5 mW

Pin loss

: Segment pin ..... 2 V

× 3 mA × 9 = 54 mW

Timing pin ......... 2 V

× 15 mA = 30 mW

LED output ........

Pull-down resistor loss ........

PT = + + = 501.5 mW

In this example, the power consumption of 501.5 mW is less than the allowable total loss for the shrink

DIP package (600 mW). However, since the allowable total loss is 450 mW for the QFP package, it is

necessary to decrease power consumption by decreasing the number of on-chip pull-down resistors. In

this example, power consumption can be adjusted to 344 mW by incorporating pull-down resistors in

only 11 digit outputs and 4 segment outputs and externally mounting pull-down resistors to the 5

remaining segment outputs.

2. Except the system clock oscillator, display controller and timer/pulse generator.

3. The operating voltage range varies depending on the cycle time.

Refer to the section describing AC

characteristics.

UPD75208 Datasheet(PDF) 39 Page - NEC

UPD75208 Datasheet(HTML) 39 Page - NEC

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62

Datasheet Download

Link URL