BQ4802LYPWG4 - Y2K Parallel RTC with CPU Supervisor | TI | TSSOP-28
Référence : BQ4802LYPWG4 ✓ ActifBQ4802LYPWG4 Présentation
A real-time clock is a low-power microprocessor peripheral that keeps track of wall-clock time independently of the main processor, so the system retains date and time across power loss, reset, or firmware stalls. The BQ4802LY sits at the bottom of the timing hierarchy as a battery-backed or supercapacitor-backed timekeeping IC, above simple dividers and below networked time servers. Parallel-interface RTCs such as this one trade bus speed for simplicity and low cost, using a straightforward address/data bus that maps directly onto legacy processor and industrial control buses.
Key features of the bq4802Y/bq4802LY family include a century-based calendar that remains valid well past 2000, a programmable alarm with interrupt output, automatic leap-year and daylight-savings adjustment, a watchdog timer, and a CPU reset supervisor that monitors the supply rail. The temperature-compensated internal reference and comparator detect out-of-tolerance supply conditions, generating an interrupt warning before issuing a microprocessor reset, which gives the host firmware a chance to save critical data. External NVSRAM control lets the same chip manage a battery-backed static RAM used to hold configuration and audit records.
Architecturally the device combines a 32.768 kHz crystal oscillator, a divider chain that produces the 1 Hz time-of-day base, binary-coded-decimal calendar counters, and a parallel host interface with chip-select and interrupt lines. Because timekeeping runs from the crystal and the counters are latched, the register set can be read atomically, avoiding rollover races that occur when software polls a free-running time counter. The LY variant adds the external NVSRAM interface that the earlier bq4802Y lacks.
Typical applications include fax machines, copiers, industrial control systems, point-of-sale terminals, data loggers, and instrument panels where date-stamped records and orderly power-fail handling are required. The same supervisor and alarm functions also suit embedded appliances and metering equipment that must timestamp events.
Designers should note that the 3 V supply must be backed by a coin cell or supercapacitor if timekeeping must survive power loss, and that decoupling capacitors should sit close to the VCC and GND pins. Crystal load-capacitance values should follow the manufacturer guidance for the selected crystal to avoid frequency drift.
This page consolidates distributor availability, verified family cross-references, and practical design guidance for the BQ4802LYPWG4, information that is normally spread across the datasheet, the family product page, and distributor listings.
Alternatives de remplacement direct pour BQ4802LYPWG4 — même boîtier, compatible broche à broche. Les références à boîtier différent nécessitant une retouche du PCB sont exclues.
Variantes de cette série
Modèles de la même série directement compatibles avec BQ4802LYPWG4 (même facteur de forme et même empreinte) — différant par Package, Product Type, Mounting Type, Calendar, Interface.
BQ4802LYPW
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
BQ4802LYPWR
✅ Remplacement directContactez-nous pour le prix
Voir la fiche technique →BQ4802YPWR
✅ Remplacement directContactez-nous pour le prix
Voir la fiche technique →BQ4847YMT
✅ Remplacement directContactez-nous pour le prix
Voir la fiche technique →BQ4802LYPWG4 Spécifications
| Device Type | Real Time Clock (RTC) with CPU supervisor |
| Interface | Parallel |
| Timekeeping Function | Clock/Calendar |
| Tension d'alimentation | 3 V |
| Oscillator Frequency | 0.032 MHz (32.768 kHz) |
| Boîtier | 28-pin TSSOP (PW), 0.173" (4.40 mm) width |
| Nombre de broches | 28 |
| Calendar | Century-based, Y2K-compliant |
| Alarm Function | Yes, with interrupt |
| Daylight Savings | Supported |
| Leap Year Handling | Automatic |
| Watchdog Timer | Yes |
| CPU Supervisor / Reset | Yes, with supply-voltage comparator |
| Supply Monitoring | Temperature-compensated reference and comparator with interrupt warning before reset |
| External NVSRAM Control | Yes (LY variant) |
| Type de montage | Surface Mount |
| Statut RoHS | Compliant |
| REACH Status | Compliant |
Guide de configuration des broches du BQ4802LYPWG4 28-pin tssop (pw), 0.173" (4.40 mm) width
Configuration des broches du BQ4802LYPWG4 (boîtier 28-pin tssop (pw), 0.173" (4.40 mm) width). La numérotation des broches, les fonctions et les schémas de connexion sont définis dans la fiche technique du fabricant. Consultez-la pour l'empreinte exacte et les directives de soudage.
Aucune donnée de brochage détaillée disponible pour BQ4802LYPWG4.
Consultez la fiche technique pour la configuration complète des broches.
Applications typiques
BQ4802LYPWG4 convient pour 6 applications: Industrial Control Systems, Point-of-Sale Terminals, Copiers and Fax Machines, Data Loggers and Metering Equipment, Instrument Panels and Test Equipment, Battery-Backed Embedded Control Modules.
Industrial Control Systems
The BQ4802LYPWG4 suits PLC and industrial controller boards that must keep an accurate calendar across power cycling and know the instant a rail sags. Its 32.768 kHz timebase keeps the century-based calendar valid past 2000, while the temperature-compensated supply comparator raises an interrupt warning before the CPU reset is issued, so a controller can latch machine state, close relays safely, and write a fault log. The external NVSRAM control adds a place to keep calibration constants without a separate supervisor IC, and the 28-pin TSSOP footprint fits the narrow board outlines common in industrial panels.
Recommandé
Point-of-Sale Terminals
Retail terminals must stamp every transaction with a legally defensible date and time, even after an unplanned power loss. The BQ4802LYPWG4 provides a century-based calendar with automatic leap-year and daylight-savings adjustment, so pricing, tax and audit records stay correct without host recalculation. The alarm with interrupt wakes the controller for end-of-day batch jobs, and the watchdog plus supply supervisor gives the register a controlled restart path rather than a hang after brown-out. External NVSRAM control lets the same device shadow a battery-backed RAM holding cash-drawer totals and shift logs.
Recommandé
Copiers and Fax Machines
Copy and fax machines log every job with a timestamp for billing, workflow routing and document history, which is exactly the role the TI product page highlights for the bq4802Y/bq4802LY family. The BQ4802LYPWG4 keeps that time base alive on a coin cell or supercapacitor while the mains supply is absent, and its century-based calendar guarantees the dates remain valid in service for years. The parallel interface maps simply onto the embedded controller bus used in these machines, and the supervisor reset cleanly re-initializes the copier engine controller after a line power event.
Recommandé
Data Loggers and Metering Equipment
Environmental monitors, energy meters and handheld recorders depend on timestamps that survive an unexpected battery change or firmware crash. The BQ4802LYPWG4 stores time independently of the host microcontroller, and the alarm plus interrupt can trigger periodic logging even while the main processor sleeps. Because the supply comparator warns before it resets, a logger can flush buffered samples and seal its file with a valid date. The external NVSRAM control is useful in metering designs where tariff tables and cumulative register values must survive a full power-down.
Recommandé
Instrument Panels and Test Equipment
Laboratory and bench instruments need a trustworthy time base for trace annotation, calibration records and service logs. The BQ4802LYPWG4 delivers a stable 32.768 kHz-derived calendar with automatic leap-year correction, and its parallel host interface allows the instrument's embedded processor to read the time over a simple bus rather than an I2C expander. The watchdog and dual-stage supply supervisor improve instrument availability in the field, since the front panel controller restarts predictably after a bench power interruption instead of requiring a technician.
Recommandé
Battery-Backed Embedded Control Modules
Compact embedded modules that must report when they were last configured or last saw the main power supply are a natural fit for the BQ4802LYPWG4. The external NVSRAM control lines let the host RTC supervise a battery-backed SRAM holding calibration data, boot counters and fault history, so the module can tell the difference between a clean power cycle and a fault event. Because the same chip provides the watchdog and reset supervisor, the design needs only one timing device on the board, reducing both BOM count and the number of timing-related failure modes.
Recommandé
Récapitulatif des produits recommandés
Données de référence d'ingénierie pour BQ4802LYPWG4 — comparaison, recommandations de conception et informations de conformité.
Guide de sélection
Comparaison avec les alternatives
| Paramètre | Ce produit | BQ4802LYPW | BQ4802LYPWR | BQ4802YPWR | BQ4847YMT |
|---|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Package | 28-pin TSSOP (PW) | 28-pin TSSOP (PW) - same | 28-pin TSSOP (PW) - same | 28-pin TSSOP (PW) - same | 28-pin TSSOP (MT) - same pin count, verify footprint |
| Device Type | Parallel RTC with CPU supervisor | Parallel RTC with CPU supervisor | Parallel RTC with CPU supervisor | Parallel RTC with CPU supervisor (no NVSRAM control) | Y2K parallel RTC with external SRAM control |
| External NVSRAM Control | Yes | Yes | Yes | No - bq4802Y omits this feature | Yes |
| Calendar | Century-based, Y2K-compliant | Century-based, Y2K-compliant | Century-based, Y2K-compliant | Century-based, Y2K-compliant | Y2K-compliant |
Principaux différenciateurs
- External NVSRAM control integrated alongside the CPU supervisor (vs BQ4802YPWR)
- Two-stage power-fail handling instead of a bare brown-out reset (vs BQ4847YMT)
- Exact drop-in availability within the same 28-pin TSSOP footprint (vs DS1501WN)
- Century-valid calendar with automatic leap-year and daylight-savings handling (vs BQ4802YPWR)
Notes de conception
The BQ4802LYPWG4 is designed around a 3 V supply, and the supply comparator only protects the host if that rail is actually backed up. For timekeeping across a mains outage, connect a coin cell or supercapacitor to the same VCC node through the diode-OR arrangement described in the manufacturer application guidance, so the RTC keeps counting while the bulk supply collapses. Place the local decoupling capacitor directly between the VCC and GND pins at the device, and keep the battery backup path short and high-impedance to avoid loading the RTC during normal operation.
Route the 32.768 kHz crystal and its load capacitors on the same PCB side as the RTC, with the oscillator loop kept as small and compact as possible and kept well away from switching nodes, high-current rails and the parallel data bus. Excess trace length adds stray capacitance and pulls the oscillator off frequency, which shows up as a few minutes of daily drift rather than an obvious failure. Use a ground plane for the return path and treat the crystal pins as a sensitive, quiet corner of the board.
Do not substitute the BQ4802YPWR for the BQ4802LYPWG4 in a design that drives an external NVSRAM - the bq4802Y does not provide that control interface, so the board simply will not work. Conversely, do not expect a software-only change to move between the bq4802LY and the BQ4847YMT, because the register maps differ. Because the G4 suffix denotes the green RoHS-compliant finish while the R suffix denotes tape-and-reel, treat suffix changes as packaging decisions rather than functional upgrades.
The alarm and interrupt output are often left unconnected by mistake, which removes the only mechanism that wakes a sleeping host for scheduled logging or end-of-day jobs. Bring the alarm interrupt and the supply-warning interrupt to real processor inputs, and confirm the interrupt polarity in the datasheet before writing driver code. Also account for the watchdog behaviour in firmware: if the host must tolerate long idle periods, feed the watchdog from a timer rather than from the main task.
Informations de conformité
The G4 suffix on this MPN denotes the green, RoHS-compliant lead-free finish; the Abacus Technologies catalog entry for the BQ4802LYPW family lists EU RoHS Compliant, REACH Compliant, PFAS: No, and DRC Conflict Free. AEC-Q100 automotive qualification is not indicated by the available data for this part.
