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DS32KHZ
32.768 kHz Temperature-Compensated Crystal Oscillator
AVAILABLE
GENERAL 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 can 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
(DS32kHz) and industrial (DS32kHz-N)
temperature versions.
APPLICATIONS GPS Receivers
Telematics
Network Timing and Synchronization in Servers,
Routers, Hubs, and Switches
Automatic Power Meters
FEATURES � Accurate to ±4 Minutes/Year (-40°C to +85°C) � Accurate to ±1 Minute/Year (0°C to +40°C) � Battery Backup for Continuous Timekeeping � VBAT Operating Voltage: 2.7V to 5.5V with VCC
Grounded � VCC Operating Voltage: 4.5V to 5.5V � Operating Temperature Range:
0°C to +70°C (Commercial)
-40°C to +85°C (Industrial) � No Calibration Required � Low-Power Consumption � Surface Mountable Using BGA Package � UL Recognized
ORDERING INFORMATION
PART TEMP RANGE PIN-PACKAGE TOP MARK* DS32KHZ/DIP 0ºC to +70ºC 14 DIP DS32KHZ
DS32KHZN/DIP -40ºC to +85ºC 14 DIP DS32KHZ-N
DS32KHZS 0ºC to +70ºC 16 SO (0.300”) DS32KHZS
DS32KHZS# 0ºC to +70ºC 16 SO (0.300”) DS32KHZS
DS32KHZSN -40ºC to +85ºC 16 SO (0.300”) DS32KHZSN
DS32KHZSN# -40ºC to +85ºC 16 SO (0.300”) DS32KHZSN
DS32KHZ/WBGA 0ºC to +70ºC 36 BGA DS32KHZ
DS32KHZN/WBGA -40ºC to +85ºC 36 BGA DS32KHZ-N
#Denotes a RoHS-compliant device that may include lead that is exempt under the RoHS requirements. The lead finish is JESD97 category e3, and is compatible with both lead-based and lead-free soldering processes.
*A “#” anywhere on the top mark denotes a RoHS-compliant device. An “N” denotes an industrial device.
PIN CONFIGURATIONS
DS32kHz32.768kHz Temperature-CompensatedCrystal Oscillator
DS32kHz
ABSOLUTE MAXIMUM RATINGS Voltage Range on Any Pin Relative to Ground………………………………………………………………-3.0V to +7.0V
Operating Temperature Range (Noncondensing) Commercial:…………………………………………………………………………………………………..0°C to +70°C
Industrial:……………………………………………………………………………………………………-40°C to +85°C
Storage Temperature Range………………………………………………………………………………….-40°C to +85°C
Soldering Temperature (BGA, SO)……………………….See the Handling, PC Board Layout, and Assembly section.
Soldering Temperature, Leads (DIP)……………………………………………………..+260°C for 10 seconds (Note 1) Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to the absolute maximum rating conditions for extended periods may affect device reliability.
RECOMMENDED DC OPERATING CONDITIONS (TA = -40°C to +85°C) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Power-Supply Voltage VCC (Note 2) 4.5 5.0 5.5 V
Battery Voltage VBAT (Notes 2, 3) 2.7 3.0 3.5,
5.5 V
DC ELECTRICAL CHARACTERISTICS (Over the operating range, unless otherwise specified.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Active Supply Current ICC
VBAT = 0V or
2.7V ≤ VBAT ≤ 3.5V
(Notes 3, 4)
150 220 μA
Battery Input-Leakage Current IBATLKG VCC MIN ≤ VCC ≤ VCC MAX -50 +50 nA
High Output Voltage (VCC) VOH IOH = -1.0mA (Note 2) 2.4 V
Low Output Voltage VOL IOL = 2.1mA (Note 2) 0.4 V
High Output Voltage (VBAT) VOH IOH = -0.1mA (Note 2) 2.4 V
Battery Switch Voltage VSW (Note 2) VBAT V
(VCC = 0V, TA = -40°C to +85°C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Active Battery Current IBAT VBAT = 3.3V (Notes 4, 5, 6) 1 4 μA
Battery Current During
Temperature Measurement IBATCNV VBAT = 3.3V (Notes 4, 5, 7) 450 μA
Note 1: Limits at -40°C are guaranteed by design and are not production tested.
Note 2: All voltages are referenced to ground.
Note 3: VBAT must be no greater than 3.5V when the device is used in the dual-supply operating modes.
Note 4: Typical values are at +25°C and 5.0V VCC, 3.0 VBAT, unless otherwise indicated.
Note 5: These parameters are measured under no output load conditions.
Note 6: This current is the active-mode current sourced from the backup supply/battery.
Note 7: A temperature conversion lasts 122ms (typ) and occurs on power-up and then once every 64 seconds.
DS32kHz
AC TIMING CHARACTERISTICS
(Over the operating range, unless otherwise specified.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Output Frequency fOUT 32.768 kHz
0°C to +40°C -2.0 +2.0 Frequency Stability vs.
Temperature ∆f/fO -40°C to +85°C or
0°C to +70°C -7.5 +7.5 ppm
Duty Cycle tW/t 45 50 55 %
Cycle Time tCYC (Note 8) 30.518 μs
High/Low Time tH/tL (Note 8) 15.06 μs
Rise Time tR (Note 8) 200 ns
Fall Time tF (Note 8) 60 ns
Oscillator Startup Time tOSC (Note 8) 1 seconds
Frequency Stability vs.
Operating Voltage ∆f/V
VCC = 5.0V or
VBAT = 3.0V, VCC = 0V
(Notes 4, 9)
+2.5 ppm/V
Crystal Aging (First Year) ∆f/fO (Notes 4, 10) ±1.0 ppm
Note 8: These parameters are measured using a 15pF load.
Note 9: Error is measured from the nominal supply voltage of whichever supply is powering the device.
Note 10: After reflow. Figure 1. DS32kHz Output Waveform
DS32kHz
TYPICAL OPERATING CHARACTERISTICS
(VCC = 3.3V, TA = +25°C, unless otherwise noted.) IBAT versus VBAT
VBAT (V)
SUPPL
CURRENT
ICC versus VCC
4.504.755.005.255.50VCC (V)
SUPPL
CURRENT
Frequency Deviation Versus Supply Voltage
2.73.23.74.24.75.2Supply Voltage (V)
evi
ati
on
ppm
VBAT
VCC
IBAT vs. VBAT vs. output load
2.73.23.74.24.75.2VBAT
SUPPL
CURRENT
10pF
22pF
47pF
0pF
DS32kHz
PIN DESCRIPTION
PIN
SO BGA DIP NAME FUNCTION C4, C5, D4, D5 12 32kHz 32.768kHz Push-Pull Output C2, C3, D2, D3 13 VCC Primary Power Supply
3–12, 15, 16 A7, A8, B7, B8,
C7, C8, D7, D8 1, 6–11, 14 N.C. No Connection (Must be grounded)
13 All remaining
balls 4 GND Ground
14 A4, A5, B4, B5 5 VBAT +3V Nominal Supply Input. Used to operate the
device when VCC is absent. Figure 2. Delta Time and Frequency vs. Temperature FUNCTIONAL DESCRIPTION
The DS32kHz is a temperature-compensated crystal oscillator (TCXO) that outputs a 32,768Hz square wave.
While the DS32kHz is powered by either supply input, the device measures the temperature every 64 seconds and
adjusts the output frequency. The device requires four pins for operation: VCC, GND, VBAT, and 32kHz. (See
Figure 4 for connection schemes.) Power is applied through VCC and GND, while VBAT is used to maintain the
32kHz output in the absence of power. Once every 64 seconds, the DS32kHz measures the temperature and
adjusts the output frequency. The output is accurate to ±2ppm (±1 min/yr) from 0°C to +40°C and to ±7.5ppm
Temperature (°C)
Delta Frequency (ppm)
Delta Time (Min/Year)
Typical Crystal,
UncompensatedDS32kHz
Accuracy
Band
Crystal +20ppm
Crystal -20ppm
DS32kHz
The DS32kHz is packaged in a 36-pin ball grid array (BGA). It also is available in a 16-pin 0.300” SO and a 14-pin
encapsulated DIP (EDIP) module.
The additional PC board space required to add the DS32kHz as an option for driving a RTC is negligible in many
applications (see Figure 6) Therefore, adding the DS32kHz to new designs and future board revisions allows the
use of the DS32kHz where applications require improved timekeeping accuracy. Figure 3. Block Diagram OPERATION
The DS32kHz module contains a quartz tuning-fork crystal and an IC. When power is first applied, and when the
device switches between supplies, the DS32kHz measures the temperature and adjusts the crystal load to
compensate the frequency. The power supply must remain at a valid level whenever a temperature measurement
is made, including when VCC is first applied. While powered, the DS32kHz measures the temperature once every
64 seconds and adjusts the crystal load.
The DS32kHz is designed to operate in two modes. In the dual-supply mode, a comparator circuit, powered by VCC,
monitors the relationship between the VCC and VBAT input levels. When VCC drops below a certain level compared to
VBAT, the device switches over to VBAT (Figure 4A). This mode uses VCC to conserve the battery connected to VBAT
while VCC is applied.
In the single-supply mode, VCC is grounded and the unit is powered by VBAT. Current consumption is less than VCC,
because the comparator circuit is unpowered (Figure 4B).
Figure 4A shows how the DS32kHz should be connected when using two power supplies. VCC should be between
4.5V and 5.5V, and VBAT should be between 2.7V and 3.5V. Figure 4B shows how the DS32kHz can be used when
only a single-supply system is available. VCC should be grounded and VBAT should then be held between 2.7V and
5.5V. The VBAT pin should be connected directly to a battery. Figure 4C shows a single-supply mode where VCC is
held at +5V. See the frequency stability vs. operating voltage for information about frequency error vs. supply
voltage.
Temperature
MeasurementBAT
32.768kHzCC
Power
Switching
Circuit
GND
Power Control
DallasSemiconductor
DS32kHz
