DS32kHz 32.768kHz Temperature-Compensated Crystal Oscillator www.maxim-ic.com GENERAL DESCRIPTION FEATURES 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 Accurate to ±4 Min/Yr (-40°C to +85°C) Accurate to ±1 Min/Yr (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 DS32kHz/DIP DS32kHz-N/DIP DS32kHz/WBGA DS32kHz-N/WBGA TEMP RANGE 0ºC to +70ºC -40ºC to +85ºC 0ºC to +70ºC -40ºC to +85ºC PIN-PACKAGE 14 DIP 14 DIP 36 BGA 36 BGA PIN CONFIGURATIONS TOP VIEW N.C. N.C. 14 2 13 VCC 3 12 32KHZ OUT 11 TPIN 10 TPIN DS32kHz 1 GND 4 VBAT 5 N.C. 6 9 N.C. N.C. 7 8 N.C. DIP BGA Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device may be simultaneously available through various sales channels. For information about device errata, click here: www.maxim-ic.com/errata. 1 of 10 REV: 041603 DS32kHz ABSOLUTE MAXIMUM RATINGS Voltage Range on Any Pin Relative to Ground Operating Temperature Range Commercial Industrial Storage Temperature Range Soldering Temperature (BGA) Soldering Temperature, Leads (DIP) -3.0V to +7.0V 0°C to +70°C -40°C to +85°C -40°C to +85°C See IPC/JEDEC J-STD-020A (2x max) (Note 1) 260°C for 10 seconds (Notes 1, 2) 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. RECOMMENDED DC OPERATING CONDITIONS (TA = -40°C to +85°C) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Power-Supply Voltage VCC 4.5 5.0 5.5 V Battery Voltage (Note 3) VBAT 2.7 3.0 3.3, 5.5 V MIN TYP MAX UNITS 150 180 µA 1 4 µA DC ELECTRICAL CHARACTERISTICS (Over the operating range, unless otherwise specified.) PARAMETER SYMBOL CONDITIONS Active Supply Current ICC (Notes 4, 5) Active Battery Current IBAT VCC = 0V, VBAT = 3.3V (Notes 4, 5, 6, 7) High Output Voltage (VCC) VOH IOH = -1.0mA Low Output Voltage VOL IOL = 2.1mA Battery Switch Voltage VSW High Output Voltage (VBAT) VOH 2.4 V 0.4 VBAT IOH = -0.1mA 2.4 V V V Note 1: Post-solder cleaning with water-washing techniques is acceptable, provided that ultrasonic vibration is not used. Such cleaning can damage the crystal. Note 2: Encapsulated DIP modules can be successfully processed through conventional wave-soldering techniques, as long as the temperature of the crystal contained inside does not exceed +150°C. Note 3: VBAT must be no greater than 3.3V 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 load conditions. Note 6: This current is the active mode current sourced from the backup supply/battery. Note 7: Battery current increases to 450µA (typ) for 122ms (typ) for every 64 seconds. 2 of 10 DS32kHz AC TIMING CHARACTERISTICS (Over the operating range, unless otherwise specified.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX 32.768 UNITS Output Frequency fOUT Frequency Stability vs. Temperature ∆f/fO Duty Cycle tW/t 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 1 s ±2.5 ppm/V ±1.0 ppm/yr 0°C to +40°C -40°C to +85°C or 0°C to +70°C -2.0 +2.0 -7.5 +7.5 45 Oscillator Startup Time tOSC Frequency Stability vs. Operating Voltage ∆f/V (Note 8) VCC = 5.0V or VBAT = 3.0V, VCC = 0V (Notes 4, 9) Crystal Aging ∆f/fO (Notes 4, 10) 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. 3 of 10 kHz 50 55 ppm % DS32kHz TYPICAL OPERATING CHARACTERISTICS (VCC = 3.3V, TA = +25°∞ C, unless otherwise noted.) ICC vs. VCC 2.5 100 75 50 2.0 1.5 3.5 4.0 4.5 5.0 5.5 10.0 7.50 22pF 6.00 10pF 0pF 0 2.5 3.0 VBAT (V) 3.5 4.0 4.5 5.0 5.5 2.5 3.0 3.5 VCC (V) FREQUENCY ERROR vs. VCC FREQUENCY ERROR vs. VBAT 2.0 DS32kHZ toc04 8 7 6 4.0 VBAT DS32kHZ toc05 3.0 47pF 2.50 25 1.5 5 ERROR (ppm) 2.5 12.5 SUPPLY CURRENT (mA) 125 SUPPLY CURRENT (mA) 3.0 15.0 DS32kHZ toc02 DS32kHZ toc01 3.5 ERROR (ppm) SUPPLY CURRENT (mA) 4.0 IBAT vs. OUTPUT LOAD vs. VCC 150 4 3 1.0 0.5 0 2 1 -0.5 0 -1.0 -1 2.5 3.0 3.5 4.0 4.5 5.0 DS32kHZ toc03 IBAT vs. VBAT 4.5 4.5 5.5 5.0 VCC (V) VBAT (V) 4 of 11 5.5 4.5 5.0 5.5 DS32kHz PIN DESCRIPTIONS PIN NAME FUNCTION BGA DIP A4, A5, B4, B5 5 VBAT +3V Batttery Supply A7, A8, B7, B8, C7, C8, D7, D8 10, 11 TPIN Test Pin (must be grounded) C2, C3, D2, D3 13 VCC C4, C5, D4, D5 12 32KHZ OUT — 1, 6–9, 14 N.C. No Connection All remaining balls 4 GND Ground Primary Power Supply 32.768kHz Output Figure 1. Delta Time and Frequency vs. Temperature 0.00 -10.00 -30.00 -40.00 -50.00 -60.00 TYPICAL CRYSTAL UNCOMPENSATED DS32kHz OUTPUT DELTA TIME (MIN/YR) -20.00 -70.00 -80.00 -90.00 -100.00 FUNCTIONAL DESCRIPTION The DS32kHz requires four pins for operation: VCC, GND, VBAT, and 32KHZ OUT. (See Figure 3 for connection schemes.) Power is applied through VCC and GND, while VBAT is used to maintain the 32kHz output in the absence of power. The output is accurate to ±7.5ppm (±4 min/yr) from –40°C to +85°C and ±2ppm (±1 min/yr) from 0°C to +40°C. The DS32kHz is packaged in a small 36-pin SMD using ball grid array (BGA) with dimensions 0.400" wide, 0.450" long, and 0.124" high. It also is available in a 14-pin DIP module. technology 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. 5 of 10 DS32kHz Figure 2. 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 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 3A). 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 that of VCC, because the comparator circuit is unpowered (Figure 3B). Figure 3A 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 3.3V. Figure 3B 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 3C shows a single supply mode where VCC is held at +5V. See the frequency stability versus operating voltage for information about frequency error versus supply voltage. Figure 3. Power-Supply Connections 6 of 10 DS32kHz Figure 4 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 ICC and IBAT 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 can increase the ICC and IBAT currents significantly and increase the current consumption of the RTC as well. Figure 5 shows one circuit that can be used to reduce the current consumption of a DS32kHz and an RTC. The values of R1 and C1 may vary depending on the RTC used. However, values of 1.0MW and 100pF are recommended as a starting point. R2 is used to shift the input waveform to the proper level. The recommended value for R2 is 33kW. Figure 4. DS32kHz Connections THE STANDARD 32.768kHz CRYSTAL AND THE DS32kHz SHOULD BE CONNECTED TO ADDRESS THE INTERCHANGEABLE OPTION. Figure 5. DS32kHz and RTC Connections THIS SHOWS A CIRCUIT THAT CAN BE USED TO REDUCE THE CURRENT CONSUMPTION OF A DS32kHz AND AN RTC. 7 of 10 DS32kHz Figure 6. DS32kHz Output Waveform RELATED APPLICATION NOTES Application Note 58: Crystal Considerations with Dallas Real-Time Clocks Application Note 701: Using the DS32kHz with Dallas RTCs PACKAGE INFORMATION (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package information, go to www.maxim-ic.com/DallasPackInfo.) G H D C PKG F E A B 8 of 10 DIM A IN B IN C IN D IN E IN F IN G IN H IN 36-PIN BGA MIN 0.395 0.445 0.022 0.047 0.047 0.347 0.118 0.020 MAX 0.405 0.455 0.028 0.053 0.053 0.353 0.130 0.030 DS32kHz PACKAGE INFORMATION (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package information, go to www.maxim-ic.com/DallasPackInfo.) 9 of 10 DS32kHz PACKAGE INFORMATION (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package information, go to www.maxim-ic.com/DallasPackInfo.) Note: Pins 2, 3 are missing by design. PKG DIM A IN B IN C IN D IN E IN F IN G IN H IN J IN K IN 14-PIN DIP MIN MAX 0.825 0.840 0.420 0.440 0.235 0.260 0.100 0.130 0.015 0.030 0.110 0.140 0.090 0.110 0.290 0.330 0.008 0.012 0.015 0.021 10 of 10