DS1677 Portable System Controller www.maxim-ic.com GENERAL DESCRIPTION FEATURES The DS1677 portable system controller is a Provides Real-Time Clock circuit that incorporates many of the functions Counts Seconds, Minutes, Hours, Date of the necessary for low-power portable products Month, Month, Day of the Week, and Year integrated into one chip. The device provides a with Leap Year Compensation Valid Up to real-time clock (RTC), NV RAM controller, 2100 microprocessor monitor, power-fail warning, and Power Control Circuitry Supports System a 3-channel, 8-bit analog-to-digital converter Power-On from Day/Time Alarm (ADC). Communication with the DS1677 is Microprocessor Monitor established through a simple 3-wire interface. Halts Microprocessor During Power-Fail Automatically Restarts Microprocessor After The RTC provides seconds, minutes, hours, day, Power Failure date, month, and year information with leap year Monitors Pushbutton for External Override compensation. The RTC also provides an alarm Halts and Resets an Out-of-Control interrupt. This interrupt works when the DS1677 Microprocessor is powered by the system power supply or when NV RAM Control in battery-backup operation so the alarm can be Automatic Battery Backup and Write used to wake up a system that is powered down. Protection to External SRAM 3-Channel, 8-Bit ADC Automatic backup and write protection of an Simple 3-Wire Interface external SRAM is provided through the V and CCO +5.0V Operation CEO pins. The backup energy source used to power the RTC is also used to retain RAM data in 1.25V Threshold Detector for Power-Fail Warning the absence of V through the V pin. CEO, CC CCO UL Recognized the chip-enable output to SRAM, is controlled during power transients to prevent data corruption. PIN CONFIGURATION TOP VIEW ORDERING INFORMATION V 1 20 ST BAT VOLTAGE PIN- DS1677 PART* TOP MARK V 2 19 V CCO CC (V) PACKAGE DS1677E 5.0 20 TSSOP DS1677-5 SCLK 3 18 X1 DS1677E+ 5.0 20 TSSOP DS1677-5 I/O 4 17 X2 * All devices are specified over the 0C to +70C operating range. CS 5 16 AIN0 A + anywhere on the top mark denotes a lead(Pb)-free device. + Denotes a lead(Pb)-free/RoHS-compliant device. 6 15 AIN1 CEI CEO 7 14 AIN2 N.C. 8 13 RST INT 9 12 PFI GND 10 11 PFO TSSOP 4.4mm 1 of 18 REV: 080905 DS1677 DETAILED DESCRIPTION The microprocessor monitor circuitry of the DS1677 provides three basic functions. First, a precision temperature-compensated reference and comparator circuit monitors the status of V . When an out-of- CC tolerance condition occurs, an internal power-fail signal is generated which forces the to RST the active state. When V returns to an in-tolerance condition, the RST signal is kept in the active state for 250ms CC to allow the power supply and processor to stabilize. The DS1677 debounces a pushbutton input and guarantees an active RST pulse width of 250ms. The third function is a watchdog timer. The DS1677 has an internal timer that forces the RST signal to the active state if the strobe input is not driven low prior to watchdog timeout. The DS1677 also provides a 3-channel 8-bit successive approximation ADC. The converter has an internal 2.55V (typical) reference voltage generated by an on-board band-gap circuit. The ADC is monotonic (no missing codes) and has an internal analog filter to reduce high-frequency noise. OPERATION The block diagram in Figure 1 shows the main elements of the DS1677. The following paragraphs describe the function of each pin. DS1677 BLOCK DIAGRAM Figure 1 2 of 18