DS1302 Datasheet, PDF (4/13 Pages) Dallas Semiconductor – Trickle Charge Timekeeping Chip

DS1302 Trickle-Charge Timekeeping Chip
PIN DESCRIPTION
PIN NAME
FUNCTION
Primary Power-Supply Pin in Dual Supply Configuration. V_CC1 is connected to a
backup source to maintain the time and date in the absence of primary power. The
1
V_CC2 DS1302 operates from the larger of V_CC1 or V_CC2. When V_CC2 is greater than V_CC1 +
0.2V, V_CC2 powers the DS1302. When V_CC2 is less than V_CC1, V_CC1 powers the
DS1302.
Connections for Standard 32.768kHz Quartz Crystal. The internal oscillator is
2
X1 designed for operation with a crystal having a specified load capacitance of 6pF.
For more information on crystal selection and crystal layout considerations, refer to
Application Note 58: Crystal Considerations for Dallas Real-Time Clocks. The
DS1302 can also be driven by an external 32.768kHz oscillator. In this
3
X2
configuration, the X1 pin is connected to the external oscillator signal and the X2 pin
is floated.
4
GND Ground
Input. CE signal must be asserted high during a read or a write. This pin has an
5
CE internal 40kΩ (typ) pulldown resistor to ground. Note: Previous data sheet revisions
referred to CE as RST. The functionality of the pin has not changed.
6
I/O
Input/Push-Pull Output. The I/O pin is the bidirectional data pin for the 3-wire
interface. This pin has an internal 40kΩ (typ) pulldown resistor to ground.
7
SCLK
Input. SCLK is used to synchronize data movement on the serial interface. This pin
has an internal 40kΩ (typ) pulldown resistor to ground.
Low-Power Operation in Single Supply and Battery-Operated Systems and Low-
Power Battery Backup. In systems using the trickle charger, the rechargeable
8
V_CC1 energy source is connected to this pin. UL recognized to ensure against reverse
charging current when used with a lithium battery. Go to www.maxim-
ic.com/TechSupport/QA/ntrl.htm.
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