Appendix A How To Measure Current Consumption; Measuring V Dd Current Consumption - Epson S5U1C17801T1100 Hardware Manual

Epson cmos 16-bit single chip microcomputer user manual software evaluation tool for s1c17801

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Appendix A How to Measure Current

For measuring current consumption of the single S1C17801 unit, jumpers (JP4,JP5,JP2) are available on the

SVT17801 CPU board. The S1C17801 has three power supplies, one for core and I/O (V

(AV

), and the other for RTC (RTCV

power supply line can be measured by inserting an ammeter among the pins after removing the jumper. Sum of the

current obtained from each power line is current consumed by the single S1C17801 unit.

A.1 Measuring V

Current consumed by the power supply for core and I/O (V

Because external components affect the measurement, some necessary process is required for each I/O pin. To

measure current consumption for the single S1C17801 as described in the S1C17801 Technical Manual, influence

by current must be controlled for "USB pins" and "STBY pins."

For information about sample software (software flow) to measure current consumption, see the S1C17801 Current

Consumption Measurement Application Note.

∗ USB Pins

Shot key diodes D3 to D6 are attached to the SVT17801 USB pins as shown in the figure A.1. The diodes attach-

ment is intended for electrostatic protection. However, current flowing through the diodes is also measured when

measuring Halt or Sleep current of the single S1C17801, and this diodes current causes deviation of the single

S1C17801 current consumption from that described in the S1C17801 Technical Manual.

J10

54819-0578

VBUS

D–

D+

GND

FG6

FG7

SN65220DBVT

FG8

FG9

GND

If each USB pin is in the following state,

• as shown in the figure A.1.,

• N.C. for each of the USB pins (D3 to D6, C51,C24,R53,C21,R25,R52,R22,R23 not installed)

Current consumption differential for V

∗ STBY Pins

The STBY pin on the SVT17801 can be controlled by GPIO(P43) as shown in the figure A.2, and pulled down

by the resistor R21 (10KΩ). The following current flows if P43 is in HIGH output state.

IR21 = 3.3(V) / 10(kΩ) = 330(μA)

To reduce current consumption in Halt or Sleep mode, set P43 to the LOW output port. Then this current is

cancelled. However, note that executing this operation while OSCI is used as a system clock causes system to halt

S5U1C17801T1100 HARDWARE MANUAL

(SOFTWARE EVALUATION TOOL FOR S1C17801)