ds2762ax-t-r Maxim Integrated Products, Inc., ds2762ax-t-r Datasheet - Page 19

• Manufacturer Part Number: ds2762ax-t-r
• Description: Ds2762 High-precision Li+ Battery Monitor With Alerts
• Manufacturer: Maxim Integrated Products, Inc.

HARDWARE CONFIGURATION
Because the 1-Wire bus has only a single line, it is important that each device on the bus be able to drive it at the
appropriate time. To facilitate this, each device attached to the 1-Wire bus must connect to the bus with open-drain
or tri-state output drivers. The DS2762 used an open-drain output driver as part of the bidirectional interface
circuitry shown in Figure 16. If a bidirectional pin is not available on the bus master, separate output and input pins
can be connected together.
The 1-Wire bus must have a pullup resistor at the bus-master end of the bus. For short line lengths, the value of
this resistor should be approximately 5kW. 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. If the
bus is left low for more than 120ms, slave devices on the bus begin to interpret the low period as a reset pulse,
effectively terminating the transaction.
Figure 16. 1-Wire Bus Interface Circuitry
TRANSACTION SEQUENCE
The protocol for accessing the DS2762 through the 1-Wire port is as follows:
§
§
§
§
The sections that follow describe each of these steps in detail.
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 DS2762 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.
Initialization
Net Address Command
Function Command
Transaction/Data
Rx
Tx
BUS MASTER
V
(2.0V to 5.5V)
Rx = RECEIVE
Tx = TRANSMIT
PULLUP
19 of 25
4.7kW
1mA
(typ)
DS2762 1-Wire PORT
100W
MOSFET
Rx
Tx