DS1482

3 of 7

Figure 2. Typical Operating Circuit

(21)

SH7622

µC

(164)

TxD0

(171)

RxD0

(32)

PTA0

(31)

PTA1

(178)

IRQ7

PCTLZ

DS1482

TXD

I/O

RXD

SPU

START

DONE

GND

IRLMS6702

RS

1-Wire

NETWORK

Selecting RS

Assuming that the series resistance of the FET in

on-condition can be neglected, the value of RS is

limited as follows:

RSmax = 0.0015 x VCCmin/I(standby,max)

RSmin = 0.01 x VCCmax/I(active,min)

Example:

VCCmin = 4.5V, VCCmax = 5.5V

I(standby,max) = 0.15mA

I(active,min) = 12mA

RSmax = 45

W, RSmin = 4.58W

To maximize available power on the 1-Wire line,

RS should be close to the lowest permissible

value, in this example 5.1

W ±5%. The effect of the

on-chip pullup resistor is negligible.

Figure 3. DS1482 Application Signals, Normal Communication

TXD

SPU, START, DONE ALL LOW

I/O

RXD

H

L

H

L

H

L

Figure 4. DS1482 Application Signals, Strong Pullup Case

TXD

SPU

RXD

I/O

START

CURRENT

1

DONE

2

3

4

H

L

H

L

H

L

PCTLZ

H

L

H

L

H

L

H

L