DS1673

3 of 18

PIN DESCRIPTION

PIN

NAME

FUNCTION

1

Battery Input for Standard 3V Lithium Cell or Other Energy Source

2

3

SCLK

Serial Clock Input. Used to synchronize data movement on the serial interface.

4

I/O

Data Input/Output. This pin is the bidirectional data pin for the 3-wire interface.

5

CS

Chip Select. Must be asserted high during a read or a write for communication over the

3-wire serial interface. CS has an internal 40k

W pulldown resistor.

6

CEI

RAM Chip-Enable In. Must be driven low to enable the external RAM.

7

CEOL

RAM Chip-Enable Out Low. Active-low chip-enable output for low-order SRAM

byte.

8

CEOH

RAM Chip-Enable Out High. Active-low chip-enable output for high-order SRAM

byte.

9

INT

Interrupt Output. This pin is an active-high output that can be used as an interrupt

input to a microprocessor. The INT output remains high as long as the status bit

causing the interrupt is present and the corresponding interrupt-enable bit is set. The

10

GND

Ground. DC power is provided to the device on this pin.

11

BHE

Byte High-Enable Input. This pin when driven low activates the

CEOH output if CEI

is also driven low.

12

BLE

Byte Low-Enable Input. This pin when driven low activates the

CEOL output if CEI is

also driven low.

13

RST

Active-Low Reset. The

RST pin functions as a microprocessor reset signal. This pin is

timed out; 3) during the power-up reset period; and 4) in response to a pushbutton

reset. The

RST pin also functions as a pushbutton reset input. When the RST pin is

driven low, the signal is debounced and timed such that a

RST signal of at least 250ms

is generated. This pin has an open-drain output with an internal 47k

W pullup resistor.

14,

15, 16

AIN2,

AIN1,

AIN0

Analog Inputs. These pins are the three analog inputs for the 3-channel ADC.

17, 18

X2, X1

Connections for Standard 32.768kHz Quartz Crystal. For greatest accuracy, the

DS1673 must be used with a crystal that has a specified load capacitance of 6pF. There

is no need for external capacitors or resistors. Note: X1 and X2 are very high-

impedance nodes. It is recommended that they and the crystal be guard-ringed with

ground and that high frequency signals be kept away from the crystal area. For more

information on crystal selection and crystal layout considerations, refer to Application

Note 58: Crystal Considerations with Dallas Real Time Clocks. The DS1673 does not

function without a crystal.

19

+3.0V or +5.0V Input DC Power

20

ST

Active-Low Strobe Input. The strobe input pin is used with the watchdog timer. If the

ST pin is not driven low within the watchdog time period, the RST pin is driven low.