Analog Devices Inc./Maxim Integrated DS1632S

Overview

DS1632S from Maxim Integrated is a PC power-fail and reset controller IC with integrated 32.768 kHz crystal oscillator, ±5% or ±10% VCC monitoring (4.25–4.75 V trip range), 95 ms / 190 ms selectable reset pulse width, and complementary open-drain PF/LB/RST outputs. It provides battery-backed RTC power switching via VCCO and supports direct interface to laptop/notebook chipsets.

For engineers reviewing the DS1632S datasheet, DS1632S pinout, DS1632S application, or DS1632S equivalent, key selection criteria include VCC fail detection tolerance selection (TOL pin), reset duration configuration (RD pin), battery backup current (<2 µA), VCCO switched output capability (100 mA), and compatibility with 6 pF load crystals for ±2 min/month RTC accuracy.

Technical Context

The DS1632S integrates three functional blocks: a precision comparator-based VCC monitor with dual trip thresholds (selected by TOL), a rail-to-rail 32.768 kHz crystal oscillator (requiring 6 pF CL crystal) that operates on VCC or VBAT ≥2.3 V, and a low-dropout power switch routing VCC/VBAT to VCCO and OSCOUT during battery backup.

Its reset logic uses RD pin state to set power-up/down delay (9/18 ms) and active reset duration (95/190 ms); all PF, LB, and RST outputs are open-drain with VOL ≤0.4 V at 4 mA sink; VCCO delivers up to 100 mA with <0.3 V dropout while preserving battery life by disabling non-critical outputs during VCC loss.

Key Specifications

Pinout & Package

DS1632S is available in 16-pin SOIC (300-mil) surface-mount package, pin-compatible with the DIP variant. All pins match Maxim's mechanical drawings for 16-pin SOIC outline.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar power-fail and reset controller applications.

Compared with DS1632S, MAX6900 omits battery backup, oscillator, and VCCO-requiring external components for RTC functionality-while DS1232L lacks low-battery signaling and configurable reset timing, limiting suitability for portable designs requiring precise power sequencing and long-term clock integrity.

Availability

DS1632S is available at Aetrix Electronics and suitable for desktop motherboard power management, laptop chipset interface, industrial panel PC power sequencing, and POS terminal battery backup applications requiring stable component supply and long-lifecycle availability.

Supply support for DS1632S includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated (now part of Analog Devices) is a U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for computing, communications, and industrial markets.

The DS1632S belongs to Maxim's PC supervisory IC product line, designed specifically to consolidate power-fail detection, reset generation, battery-backed RTC power switching, and oscillator functions into a single chip for x86 and compatible embedded platforms.

FAQ

What is the function of the RD pin on the DS1632S?

The RD pin on the DS1632S selects reset pulse duration: tied to GND yields 95 ms, tied to VCC yields 190 ms. This setting applies identically to power-up, power-down, and pushbutton-initiated reset events. The DS1632S uses this single pin to configure timing without external components, ensuring compliance with processor reset hold-time requirements across varying power conditions.

Does the DS1632S require an external crystal?

Yes, the DS1632S requires an external 32.768 kHz tuning-fork crystal connected between X1 and X2. It is optimized for crystals with 6 pF load capacitance (e.g., Daiwa DT26S or Seiko DS-VT-200). The DS1632S contains the oscillator circuitry but not the resonator; omitting the crystal disables RTC functionality and prevents OSCOUT and VCCO operation during battery backup.

How does the DS1632S handle power switching between VCC and VBAT?

The DS1632S uses an internal low-dropout switch to route the higher of VCC or VBAT to VCCO and OSCOUT. When VCC ≥ VBAT, VCC powers those outputs; when VCC fails below VBAT (≥2.3 V), VBAT takes over with <0.3 V dropout. All other outputs enter high-Z or grounded state to minimize battery drain-ensuring DS1632S draws <2 µA from VBAT during extended backup.

Can the DS1632S be used with a 3.3 V system?

No, the DS1632S is specified only for 4.5–5.5 V VCC operation and 2.3–3.5 V VBAT input. Its VCC monitoring thresholds (4.25–4.75 V), internal comparators, and output drive levels are calibrated for +5 V systems. Using it with 3.3 V violates absolute maximum ratings and invalidates trip point accuracy; for 3.3 V supervision, consider the DS1233Z or MAX6315 series instead of DS1632S.

What is the purpose of the TOL pin on the DS1632S?

The TOL pin on the DS1632S selects the VCC monitoring tolerance: grounded for ±5% detection (trip range 4.50–4.75 V), connected to VCC for ±10% (4.25–4.50 V). This allows designers to match DS1632S behavior to their power supply's regulation spec-tighter tolerance for high-reliability servers, looser for cost-optimized consumer laptops-without changing the DS1632S part number or layout.