DS2703 데이터 시트보기 (PDF) - Dallas Semiconductor -> Maxim Integrated

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DS2703

SHA-1 Battery Pack Authentication IC

Dallas Semiconductor -> Maxim Integrated 

DS2703 SHA-1 Battery Pack Authentication IC

HARDWARE CONFIGURATION

The DS2703 uses an open-drain output driver as part of the bidirectional interface circuitry shown in Figure 5. If a

bidirectional pin is not available on the bus master, separate output and input pins can be connected together. For

normal communication the 1-Wire bus must have a pullup resistor at the bus-master end of the bus. For short line

lengths and/or VPULLUP ≥ 3.0V, a value of approximately 4.7kW is recommended. For long line lengths and/or

VPULLUP < 3.0V, a value of approximately 2kW is recommended. The idle state for the 1-Wire bus is high. If, for any

reason, a bus transaction must be suspended, the bus must be left in the idle state to properly resume the

transaction later. Note that if the bus is left low for more than tLOW0, slave devices on the bus begin to interpret the

low period as a reset pulse, effectively terminating the transaction.

When performing SHA-1 computations, the DS2703 requires a stronger pullup than 4.7k. A P-FET in parallel with

the standard pullup can be switched on during computation and then disabled to read the result. When measuring

the thermistor RTHM, both the strong pullup and standard pullup should be disabled to allow a weak pullup to form a

voltage divider with the thermistor. A voltage A/D connected directly to the 1-Wire bus can then read the voltage

drop of the thermistor.

Figure 5. 1-Wire Bus Interface Circuitry

VPULLUP

COMP

COMM

Voltage A/D

Rx

Tx

Bus Master

4.7K 50K

150

DQ

~1µA

RTHM

Rx

~100Ω

Tx

MOSFET

PACK-

DS2703

Activate

THM

TRANSACTION SEQUENCE

The protocol for accessing the DS2703 through the 1-Wire port is as follows:

§ Initialization

§ Net Address Command

§ Function Command(s)

§ Data Transfer (not all commands have data transfer)

All transactions of the 1-Wire bus begin with an initialization sequence consisting of a reset pulse transmitted by the

bus master, followed by a presence pulse simultaneously transmitted by the DS2703 and any other slaves on the

bus. The presence pulse tells the bus master that one or more devices are on the bus and ready to operate. For

more details, see the 1-Wire Signaling section below.

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