DS1302Z+ Maxim Integrated Products, DS1302Z+ Datasheet - Page 7

• Manufacturer Part Number: DS1302Z+
• Description: IC TIMEKEEPER W/CHARGER 8-SOIC
• Manufacturer: Maxim Integrated Products
• Type: Clock/Calendar/Trickle-Chargerr

Specifications of DS1302Z+

• Memory Size: 31B
• Time Format: HH:MM:SS (12/24 hr)
• Date Format: YY-MM-DD-dd
• Interface: 3-Wire Serial
• Voltage - Supply: 2 V ~ 5.5 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Function: Clock/Calendar/Trickle Charger/NV Timekeeping RAM
• Rtc Memory Size: 31 Byte
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 2 V
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Mounting Style: SMD/SMT
• Rtc Bus Interface: Serial (3-Wire)
• Supply Current: 1.2 mA
• Clock Format: HH
• Clock Ic Type: RTC
• Ic Interface Type: 3 Wire
• Memory Configuration: 31 X 8
• Supply Voltage Range: 2V To 5.5V
• Digital Ic Case Style: SOIC
• No. Of Pins: 8
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

CLOCK HALT FLAG
Bit 7 of the seconds register is defined as the clock halt (CH) flag. When this bit is set to logic 1, the clock oscillator
is stopped and the DS1302 is placed into a low-power standby mode with a current drain of less than 100nA. When
this bit is written to logic 0, the clock will start. The initial power-on state is not defined.
WRITE-PROTECT BIT
Bit 7 of the control register is the write-protect bit. The first seven bits (bits 0 to 6) are forced to 0 and always read 0
when read. Before any write operation to the clock or RAM, bit 7 must be 0. When high, the write-protect bit
prevents a write operation to any other register. The initial power-on state is not defined. Therefore, the WP bit
should be cleared before attempting to write to the device.
TRICKLE-CHARGE REGISTER
This register controls the trickle-charge characteristics of the DS1302. The simplified schematic of Figure 5 shows
the basic components of the trickle charger. The trickle-charge select (TCS) bits (bits 4 to 7) control the selection of
the trickle charger. To prevent accidental enabling, only a pattern of 1010 enables the trickle charger. All other
patterns will disable the trickle charger. The DS1302 powers up with the trickle charger disabled. The diode select
(DS) bits (bits 2 and 3) select whether one diode or two diodes are connected between V
one diode is selected or if DS is 10, two diodes are selected. If DS is 00 or 11, the trickle charger is disabled
independently of TCS. The RS bits (bits 0 and 1) select the resistor that is connected between V
resistor and diodes are selected by the RS and DS bits as shown in Table 2.
Table 2. Trickle Charger Resistor and Diode Select
Diode and resistor selection is determined by the user according to the maximum current desired for battery or
super cap charging. The maximum charging current can be calculated as illustrated in the following example.
Assume that a system power supply of 5V is applied to V
that the trickle charger has been enabled with one diode and resistor R1 between V
current I
As the super cap charges, the voltage drop between V
decreases.
BIT 7
TCS
X
X
X
1
1
1
1
1
1
0
MAX
BIT 6
would therefore be calculated as follows:
TCS
X
X
X
0
0
0
0
0
0
1
BIT 5
TCS
X
X
X
1
1
1
1
1
1
0
I
MAX
BIT 4
= (5.0V – diode drop) / R1 ≈ (5.0V – 0.7V) / 2kΩ ≈ 2.2mA
TCS
X
X
X
0
0
0
0
0
0
1
BIT 3
DS
X
0
0
0
1
1
1
1
0
1
BIT 2
DS
X
0
1
1
1
1
0
0
0
1
7 of 13
CC2
CC2
BIT 1
and V
RS
X
X
0
0
1
1
0
1
1
0
and a super cap is connected to V
CC1
BIT 0
decreases and therefore the charge current
RS
X
X
0
1
0
1
1
0
1
0
CC2
Initial power-on state
2 Diodes, 2kΩ
2 Diodes, 4kΩ
2 Diodes, 8kΩ
CC2
and V
FUNCTION
1 Diode, 2kΩ
1 Diode, 4kΩ
1 Diode, 8kΩ
Disabled
Disabled
Disabled
and V
CC1
CC2
CC1
. The maximum
CC1
. Also assume
and V
. If DS is 01,
CC1
. The