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DS1685QN-3+ Datasheet(PDF) 5 Page - Maxim Integrated Products |
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DS1685QN-3+ Datasheet(HTML) 5 Page - Maxim Integrated Products |
5 / 34 page DS1685/DS1687 3V/5V Real-Time Clocks 5 of 34 PIN DESCRIPTIONS (continued) PIN DS1685 DS1687 PDIP, SO, TSSOP PLCC EDIP NAME FUNCTION 18 22 18 KS Kickstart Input, Active Low. When VCC is removed from the DS1685/DS1687, the system can be powered on in response to an active- low transition on the KS pin, as might be generated from a key closure. VBAUX must be present and the auxiliary-battery enable bit (ABE) and kick- start enable bit (KSE) must be set to 1 if the kickstart function is used, and the KS pin must be pulled up to the V BAUX supply. While VCC is applied, the KS pin can be used as an interrupt input. If not used, connect to V CC, or to VBAUX if VBAUX is used. 19 23 19 IRQ Interrupt-Request Output, Open Drain, Active Low. The IRQ pin is an active-low output of the DS1685/DS1687 that can be connected to the interrupt input of a processor. The IRQ output remains low as long as the status bit causing the interrupt is present and the corresponding interrupt- enable bit is set. To clear the IRQ pin, the application software must clear all the enabled flag bits contributing to IRQ’s active state asserted but without asserting CS latch addresses. However, no data transfer occurs. 20 24 — VBAT Battery Input for Any Standard 3V Lithium Cell or Other Energy Source. Battery voltage must be held between 2.5V and 3.7V for proper operation. VBAT must be grounded if not used. Diodes should not be placed between VBAT and the battery. See “Conditions of Acceptability” at www.maxim-ic.com/UL. 21 25 21 RCLR RAM Clear Input, Active Low. If enabled by software, taking RCLR low clears the 242 bytes of user RAM to FFh. When enabled, RCLR can be activated whether or not VCC is present. The RCLR function is designed to be used by a human interface (shorting to ground manually or by a switch) and not to be driven with external buffers. This pin is internally pulled up. Do not use an external pullup resistor on this pin. 22 26 22 VBAUX Auxiliary Battery Input. Required for kickstart and wake-up features. This input also supports clock/ calendar and user RAM if VBAT is at lower voltage or is not present. A standard +3V lithium cell or other energy source can be used. Battery voltage must be held between +2.5V and +3.7V for proper operation. If VBAUX is not going to be used it should be grounded, and Auxiliary-Battery Enable bit bank 1, register 4BH, should be written to 0. See “Conditions of Acceptability” at www.maxim-ic.com/UL. 23 27 23 SQW Square-Wave Output. The SQW pin provides a 32kHz square-wave output, tREC, after a power-up condition has been detected. This condition sets the following bits, enabling the 32kHz output; DV1 = 1, and E32K = 1. A square wave is output on this pin if either SQWE = 1 or E32K = 1. If E32K = 1, then 32kHz is output regardless of the other control bits. If E32K = 0, then the output frequency is dependent on the control bits in register A. The SQW pin can output a signal from one of 13 taps provided by the 15 internal divider stages of the RTC. The frequency of the SQW pin can be changed by programming Register A as shown in Table 3. The SQW signal can be turned on and off using the SQWE bit in register B or the E32K bit in extended register 4Bh. A 32kHz SQW signal is output when the enable- 32kHz (E32K) bit in extended register 4Bh is a logic 1 and VCC is above VPF. A 32kHz square wave is also available when VCC is less than VPF if E32K = 1, ABE = 1, and voltage is applied to the VBAUX pin. 24 28 24 VCC DC Power for Primary Power Supply. When VCC is applied within the normal limits, the device sis fully accessible and data can be written and read. When VCC is below VPF reads and writes are inhibited. |
Similar Part No. - DS1685QN-3+ |
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Similar Description - DS1685QN-3+ |
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