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100801
FEATURES
Accurate to 4 Min/Yr (-40C to +85C)
Accurate to 1 Min/Yr (0C to 40C)
Battery back up for continuous timekeeping
V
BAT
operating voltage: 2.7V to 5.5V with
V
CC
grounded
V
CC
operating voltage: 4.5V to 5.5V
Operating temperature range:
0
C to 70C (Commercial)
-40
C to +85C (Industrial)
No calibration required
Low-power consumption
Surface mountable using BGA package
V
CC
:
C2, C3, D2, D3
V
BAT
:
A4, A5, B4, B5
32kHz:
C4, C5, D4, D5
GND:
All Remaining Balls
T
PIN
:
A7, A8, B7, B8, C7, C8,
D7, D8
PIN ASSIGNMENT
PIN DESCRIPTION
V
CC
- Primary Power Supply
V
BAT
- +3V Battery Supply
GND
- Ground
NC
- No Connect
T
PIN
- Test Pin (Must Be Grounded)
DESCRIPTION
The DS32kHz is a temperature-compensated crystal oscillator (TCXO) with an output frequency of
32.768kHz. This device addresses applications requiring better timekeeping accuracy and may be used to
drive the X1 input of most Dallas Semiconductor real-time clocks (RTCs), chipsets, and other ICs
containing RTCs. This device is available in commercial and industrial temperature versions, DS32kHz
and DS32kHz-N respectively.
DS32kHz
32.768kHz TCXO
www.maxim-ic.com
A
B
D
C
DS32kHz 36-Pin SMD
(Top View)
1
2
3
4
5
6
7
8
9
ORDERING INFORMATION
DS32kHz/BGA
36-Pin BGA
0C to +70C
DS32kHz-N/BGA
36-Pin BGA
-40c to +85C
DS32kHz/DIP
14-Pin DIP
0C to +70C
DS32kHz-N/DIP
14-Pin DIP
-40c to +85C
NC
V
CC
32kHz OUT
T
PIN
T
PIN
NC
NC
1
2
3
4
5
6
7
14
13
12
11
10
9
8
DS32kHz
14-Pin DIP Module (300-mil)
NC
GND
V
BAT
NC
NC
1
2
3
4
5
6
7
8
9
GND
GND
GND
V
BAT
V
BAT
GND
T
PIN
T
PIN
GND
GND
V
CC
V
CC
32kHz Out
32kHz Out
GND
T
PIN
T
PIN
GND
DS32kHz
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The DS32kHz requires four pins for operation: 1) V
CC
, 2) GND, 3) V
BAT
, and 4) 32kHz OUT. (See
Figures 1, 2, and 3 for connection schemes.) Power is applied via V
CC
and GND, while V
BAT
is used to
maintain the 32kHz output in the absence of power. The output is accurate to
7.5 ppm (4 min/yr) from
-40
C to +85C and 2 ppm (1 min/yr) from 0C to 40C.
The DS32kHz is packaged in a small, 36-pin SMD using ball grid array (BGA) technology with
dimensions 0.400 inches wide, 0.450 inches long, and 0.180 inches high. It also is available in a 14-pin
DIP module.
The additional board space required is negligible in most applications and, therefore, the recommended
land pattern layout should be implemented on all new designs and future board revisions to satisfy
applications requiring better timekeeping accuracy
.
DELTA TIME AND FREQUENCY vs. TEMPERATURE
DS32kHz BLOCK DIAGRAM
OPERATION
The DS32kHz module contains a crystal and an IC. While powered, the DS32kHz peridocially measures
the temperature and adjusts the crystal load to compensate.
The DS32kHz is designed to operate in two modes. In the dual-supply mode, a comparator circuit,
powered by V
CC,
monitors the relationship between the V
CC
and V
BAT
input levels. When V
CC
drops
D
E
LTA
TIME
(MIN
/
Y
R
)
0.00
-10.00
-20.00
-30.00
-40.00
-50.00
-60.00
-70.00
-80.00
-90.00
-100.00
DS32kHz
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below a certain level compared to V
BAT
, the device switches over to V
BAT
. (See Figure 1.0.) This mode
uses V
CC
to conserve the battery connected to V
BAT
while V
CC
is applied.
In the single-supply mode, V
CC
is grounded and the unit is powered by V
BAT
. Current consumption is less
than that of V
CC
, because the comparator circuit is unpowered. (See Figure 2.0.)
POWER SUPPLY CONNECTIONS Figures 1.0 and 2.0
Figure 1.0 shows how the DS32kHz should be connected when using two power supplies. V
CC
should be
between 4.5V and 5.5V and V
BAT
should be between 2.7V and 3.3V. Figure 2.0 shows how the DS32kHz
can be used when only a single-supply system is available. V
CC
should be grounded and V
BAT
should then
be held between 2.7V and 5.5V. The V
BAT
pin should be connected directly to a battery using no external
components.
DS32kHz CONNECTIONS Figures 3.0 and 4.0
Figure 4.0
Figure 1.0
Figure 2.0
Figure 3.0
DS32kHz
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Figure 3.0 illustrates how a standard 32.768kHz crystal and the DS32kHz should be connected to address
the interchangeable option. Using this connection scheme and the recommended layout provides a
solution, which requires no hardware modifications. Only one device should be used at a time, and both
layouts should be located very close together if the recommended layout is not used.
The DS32kHz I
CC
and I
BAT
currents are specified with no output loads. Many RTC oscillator circuits use
a quartz crystal or resonator. Driving the oscillator circuit with the rail-to-rail output of the DS32kHz may
increase the I
CC
and I
BAT
currents significantly and increase the current consumption of the RTC as well.
Figure 4 shows one recommended circuit that can be used to reduce the current consumption of a
DS32kHz and an RTC. The values of R1 and C1 will vary depending on the RTC used. However, values
of 1.0M
W and 100pF are recommended as a starting point.
RELATED APPLICATION NOTES
Application Note 58 Crystal Considerations with Dallas Real-Time Clocks
Application Note 701 Using the DS32kHz with Dallas RTCs
RECOMMENDED DC OPERATING CONDITIONS
(-40
C to +85C)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS NOTES
Power Supply Voltage
V
CC
4.5
5.0
5.5
V
Battery Voltage
V
BAT
2.7
3.0
3.3, 5.5
V
1
DC ELECTRICAL CHARACTERISTICS
(Over the operating range*)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS NOTES
Active Supply Current
I
CC
150
180
mA
2,5
Active Battery Current
(V
CC
= 0V, V
BAT
= 3.3V)
I
BAT
1
4
mA
2,3,5
High Output Voltage (V
CC
)
(I
OH
= -1.0mA)
V
OH
2.4
V
Low Output Voltage
(I
OL
= 2.1mA)
V
OL
0.4
V
Battery Switch Voltage
V
SW
V
BAT
V
High Output Voltage (V
BAT
)
(I
OH
= -0.1mA)
V
OH
2.4
V
*Unless otherwise specified.
DS32kHz
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ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground
-3.0V to +7.0V
Operating Temperature
0
C to 70C (Commercial)
-40
C to +85C (Industrial)
Storage Temperature
-40
C to +85C
Soldering Temperature
See J-STD-020A specification. (Two times max.)
* This is a stress rating only and functional operation of the device at these or any other conditions above
those indicated in the operation sections of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods of time may affect reliability.
AC TIMING CHARACTERISTICS
(Over the operating range*)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS NOTES
Output Frequency
f
OUT
32.768
kHz
Frequency Stability vs Temp
(0
C to 40C)
Df/f
O
-3.0
+1
+2.0
ppm
(-40
C to +85C)
-7.5
+7.5
Duty Cycle
T
W
/T
45
50
55
%
Cycle Time
t
CYC
30.518
ms
4
High/Low Time
t
H
/t
L
15.06
ms
4
Rise Time
t
R
200
ns
4
Fall Time
t
F
60
ns
4
Oscillator Start-Up Time
t
OSC
1
sec
4
Frequency Stability vs
Operating Voltage
(3.3V Nom)
Df/
V
1.0
ppm/
V
Crystal Aging
Df/f
O
1.0
ppm/yr
6
*Unless otherwise specified.
NOTES:
1. V
BAT
must be no greater than 3.3V when the device is used in the dual-supply operating modes.
2. Typical values are at +25C and 5.0V V
CC
unless otherwise indicated.
3. This current is the active mode current sourced from the backup supply/battery.
4. These parameters are measured using a 15pF load.
5. These parameters are measured under no load conditions.
6. After reflow.
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