I2C 32-Bit Binary Counter RTC - Maxim Integrated

1 1 of 15 GENERAL DESCRIPTION The DS1672 incorporates a 32-Bit Counter and power-monitoring functions. The 32-Bit Counter is designed to count seconds and can be used to derive time-of-day, week, month, month, and year by using a software algorithm. A precisio n, temperature-compensated reference and comparator circuit monitors the status of VCC. When an out-of-tolerance condition occurs, an internal power-fail signal is generated that forces the reset to the active state. When VCC returns to an in-tolerance condition, the reset signal is kept in the active state for a period of time to allow the power supply and processor to stabilize.

2 FEATURES 32-Bit Counter I2C Serial Interface Automatic Power-Fail Detect and Switch Circuitry Power-Fail Reset Output Low-Voltage Oscillator Operation ( min) Trickle-Charge Capability Underwriters Laboratories (UL) Recognized -40 C to +85 C Operating Range PIN CONFIGURATION . TYPICAL OPERATING CIRCUIT PDIP SO SOP TOP VIEW 1 2 3 4 8 7 6 5 VCC RST SCL SDA X1 X2 VBACK UP GND DS1672 DS1672 I2C 32-Bit Binary Counter RTC 19-6032; Rev 9/11 DS1672 2 of 15 ORDERING INFORMATION PART TEMP RANGE VOLTAGE (V) PIN-PACKAGE TOP MARK* DS1672-2+ -40 C to +85 C 8 PDIP (300 mils) DS1672-2 DS1672-3+ -40 C to +85 C 8 PDIP (300 mils) DS1672-3 DS1672-33+ -40 C to +85 C 8 PDIP (300 mils) DS1672-33 DS1672S-2+ -40 C to +85 C 8 SO (150 mils) D1672-2 DS1672S-3+ -40 C to +85 C 8 SO (150 mils) D1672-3 DS1672S-33+ -40 C to +85 C 8 SO (150 mils) D167233 DS1672S-3+T&R -40 C to +85 C 8 SO (150 mils)/Tape and Reel D1672-3 DS1672S-33+T&R -40 C to +85 C 8 SO (150 mils)/Tape and Reel D167233 DS1672U-2+ -40 C to +85 C 8 SOP(3mm)

3 1672 rr -2 DS1672U-3+ -40 C to +85 C 8 SOP(3mm) 1672 rr -3 DS1672U-33+ -40 C to +85 C 8 SOP(3mm) 1672 rr -33 DS1672U-33+T&R -40 C to +85 C 8 SOP(3mm)/Tape and Reel 1672 rr -33 + Denotes a lead-free/RoHS-compliant device. * A + anywhere on the top mark denotes a lead-free device. rr = 2-digit alphanumeric revision code. DS1672 3 of 15 ABSOLUTE MAXIMUM RATINGS Voltage Range on Any Pin Relative to to + Operating Temperature Range (noncondensing) ..-40 C to +85 C Storage Temperature C to +125 C Soldering Temperature (reflow).. +260 C Lead Temperature (soldering, 10s) .. +260 C This is a stress rating only and functional operation of the device at these or any other conditions beyond those indicated in the operation sections of this specification is not implied.

4 Exposure to absolute maximum rating conditions for extended periods of time can affect device reliability. RECOMMENDED OPERATING CONDITIONS (TA = -40 C to +85 C) (Note 1) PARAMETER SYMBOL MIN TYP MAX UNITS Supply Voltage DS1672-2 VCC V DS1672-3 VCC DS1672-33 VCC Logic 1 VIH x VCC VCC + V Logic 0 VIL + x VCC V Backup Supply Voltage VBACKUP V Note 1: All voltages referenced to ground. DC ELECTRICAL CHARACTERISTICS (VCCMIN < VCC < VCCMAX, TA = -40 C to +85 C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Active Supply Current (Note 2) ICCA -2: VCC = 600 A -3: VCC = -33: VCC = Standby Current (Note 3) ICCS -2: VCC = 500 A -3: VCC = -33: VCC = Power-Fail Voltage VPF -2: V -3: -33: VBACKUP Leakage Current IBACKUPLKG 25 50 nA Logic 0 Output (Note 4) IOL VOL = 3 mA Logic 0 Output (Note 4, DS1672-2 Only) IOL VCC > 2V; VOL = 3 mA VCC < 2V; VOL = VCC * Note 1: All voltages referenced to ground.

5 Note 2: ICCA specified with SCL clocking at max frequency (400kHz), trickle charger disabled. Note 3: ICCS specified with VCC = VCCTYP and SDA, SCL = VCCTYP, trickle charger disabled. Note 4: SDA and RST. DS1672 4 of 15 DC ELECTRICAL CHARACTERISTICS (VCC = 0V, TA = -40 C to +85 C.) (Note 5) PARAMETER SYMBOL MIN TYP MAX UNITS VBACKUP Current (Oscillator On) IBACKUPOSC 1 A VBACKUP Current (Oscillator Off) IBACKUP 200 nA Note 5: Using the recommended crystal on X1 and X2. CRYSTAL SPECIFICATIONS* PARAMETER SYMBOL MIN TYP MAX UNITS Nominal Frequency fO kHz Series Resistance ESR 45 k Load Capacitance CL 6 pF *The crystal, traces, and crystal input pins should be isolated from RF generating signals.

6 Refer to Application Note 58: Crystal Considerations for Dallas Real-Time Clocks for additional specifications DS1672 5 of 15 AC ELECTRICAL CHARACTERISTICS (VCC = 0V, TA = -40 C to +85 C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS SCL Clock Frequency fSCL Fast mode 100 400 kHz Standard mode 100 Bus Free Time Between a STOP and START Condition tBUF Fast mode s Standard mode Hold Time (Repeated) START Condition (Note 6) tHD:ST A Fast mode s Standard mode LOW Period of SCL Clock tLOW Fast mode s Standard mode HIGH Period of SCL Clock tHI GH Fast mode s Standard mode Setup Time for a Repeated START Condition tSU:STA Fast mode s Standard mode Data Hold Time (Notes 7, 8) tHD:DAT Fast mode 0 s Standard mode 0 Data Setup Time (Note 9) tSU.

7 DAT Fast mode 100 ns Standard mode 250 Rise Time of Both SDA and SCL Signals (Note 10) tR Fast mode 20 + 300 ns Standard mode 1000 Fall Time of Both SDA and SCL Signals (Note 10) tF Fast mode 20 + 300 ns Standard mode 300 Setup Time for STOP Condition tSU:STO Fast mode s Standard mode Capacitive Load for Each Bus Line (Note 10) CB 400 pF I/O Capacitance CI/O 10 pF Note 6: After this period, the first clock pulse is generated. Note 7: A device must internally provide a hold time of at least 300ns for the SDA signal (referenced to the VIHMIN of the SCL signal) in order to bridge the undefined region of the falling edge of SCL.

8 Note 8:The maximum tHD:DAT has only to be met if the device does not stretch the LOW period (tLOW) of the SCL signal. Note 9: A fast-mode device can be used in a standard-mode system, but the requirement tSU:DA T to 250ns must then be met. This will automatically be the case if the device does not stretch the LOW period of the SCL signal. If such a device does stretch the LOW period of the SCL signal, it must output the next data bit to the SDA line tR max + tSU:DA T = 1000 + 250 = 1250ns before the SCL line is released. Note 10: CB Total capacitance of one bus line in pF. DS1672 6 of 15 POWER-UP/POWER-DOWN CHARACTERISTICS (TA = -40 C to +85 C) PARAMETER SYMBOL MIN TYP MAX UNITS VCC Detect to RST (VCC Falling) tRPD 10 s VCC Detect to RST (VCC Rising) (Note 11) tRPU 250 ms VCC Fall Time; VPF(MAX) to VPF(MIN) tF 300 s VCC Rise Time; VPF(MIN) to VPF(MAX) tR 0 s Note 11: If the EOSC bit in the control register is set to logic 1, tRPU is equal to 250ms plus the startup time of the crystal oscillator.

9 Warning: Negative undershoots below while the part is in battery-backed mode can cause loss of data. Figure 1. Timing Diagram SCLSTARTSDASTOPtBUFREPEATEDSTARTtHD:STAt LOWtHD:STAtHD:DATtSU:DATtHIGHtSU:STAtFtS U:STO Figure 2. Power-Up/Power-Down Timing OUTPUTS VCC VPF(max) INPUTS HIGH IMPEDANCE RST DON'T CARE VALID RECOGNIZED RECOGNIZED VALID tRPD VPF(min) tF tPD tR tRPU DS1672 7 of 15 PIN DESCRIPTION PIN NAME FUNCTION 1, 2 X1, X2 Connections for Standard Quartz Crystal. The internal oscillator circuitry is designed for operation with a crystal having a specified load capacitance (CL) of 6pF. For more information about crystal selection and crystal layout considerations, refer to Application Note 58: Crystal Considerations with Dallas Real-Time Clocks.

10 The DS1672 can also be driven by an external oscillator. In this configuration, the X1 pin is connected to the external oscillator signal and the X2 pin is left unconnected. 3 VBACKUP Battery Input for Any Standard 3V Lithium Cell or Other Energy Source. Battery voltage must be held between and for proper operation. Diodes placed in series between the power source and the VBACKUP pin may result in improper operation. If a backup supply is not required, VBACKUP must be grounded. UL recognized to ensure against reverse charging current when used in conjunction with a lithium battery (charger disabled). See Conditions of Acceptability at 4 GND Ground.