DS1340U-33+ Maxim Integrated Products, DS1340U-33+ Datasheet - Page 7

• Manufacturer Part Number: DS1340U-33+
• Description: IC RTC I2C W/CHARGER 3.3V 8-USOP
• Manufacturer: Maxim Integrated Products
• Type: Clock/Calendar/Trickle-Chargerr

Specifications of DS1340U-33+

• Time Format: HH:MM:SS (24 hr)
• Date Format: YY-MM-DD-dd
• Interface: I²C, 2-Wire Serial
• Voltage - Supply: 2.97 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Function: Clock/Calendar/Trickle Charger
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 2.97 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Rtc Bus Interface: Serial (I2C)
• Supply Current: 192 uA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Memory Size: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

when V
maintained from the V
returned to nominal levels (Table 1). After V
above V
The DS1340 uses an external 32.768kHz crystal. The
oscillator circuit does not require any external resistors
or capacitors to operate. Table 2 specifies several crys-
tal parameters for the external crystal. Figure 3 shows a
functional schematic of the oscillator circuit. If using a
crystal with the specified characteristics, the startup
time is usually less than one second.
The initial clock accuracy depends on the accuracy of
the crystal and the accuracy of the match between the
capacitive load of the oscillator circuit and the capaci-
tive load for which the crystal was trimmed. Additional
error is added by crystal frequency drift caused by
temperature shifts. External circuit noise coupled into
the oscillator circuit can result in the clock running fast.
Figure 4 shows a typical PC board layout for isolating
Table 2. Crystal Specifications*
* The crystal, traces, and crystal input pins should be isolated
from RF generating signals. Refer to Application Note 58:
Crystal Considerations for Dallas Real-Time Clocks for addi-
tional specifications.
Figure 3. Oscillator Circuit Showing Internal Bias Network
Nominal
Frequency
Series Resistance
Load Capacitance
PARAMETER
CC
PF
C
L
1
, read and write access is allowed t
X1
drops below V
CRYSTAL
SYMBOL MIN
RTC
ESR
C
f
O
L
X2
BACKUP
BACKUP
C
Oscillator Circuit
L
2
Clock Accuracy
32.768
source until V
TYP
COUNTDOWN
12.5
. The registers are
CHAIN
_____________________________________________________________________
REGISTERS
RTC
MAX
80
CC
REC
I
2
returns
.
UNITS
CC
C RTC with Trickle Charger
kHz
kΩ
pF
is
the crystal and oscillator from noise. Refer to
Application Note 58: Crystal Considerations with Dallas
Real-Time Clocks (www.maxim-ic.com/RTCapps) for
detailed information.
The DS1340C integrates a standard 32,768Hz crystal
into the package. Typical accuracy with nominal V
and +25°C is approximately +15ppm. Refer to
Application Note 58 for information about crystal accu-
racy vs. temperature.
The DS1340 operates as a slave device on the serial
bus. Access is obtained by implementing a START
condition and providing a device identification code fol-
lowed by data. Subsequent registers can be accessed
sequentially until a STOP condition is executed. The
device is fully accessible and data can be written and
read when V
V
blocked from any access. If V
the device power is switched from V
when V
V
V
ters are maintained from the V
is returned to nominal levels. The functional diagram
(Figure 5) shows the main elements of the serial RTC.
Figure 4. Layout Example
CC
BACKUP
BACKUP
LOCAL GROUND PLANE (LAYER 2)
falls below V
CC
, the device power is switched from V
when V
drops below V
CRYSTAL
CC
is greater than V
CC
PF
, the internal clock registers are
drops below V
PF
PF
BACKUP
. If V
is less than V
PF
PF
BACKUP
X1
X2
GND
DS1340C Only
. However, when
Operation
source until V
CC
is greater than
to V
. The regis-
BACKUP
BACKUP
CC
CC
CC
to
7
,