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Analog Devices Inc./Maxim Integrated DS1238AS-5
- Part No.:
- DS1238AS-5
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- 16-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
DS1238AS-5.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,945
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Product details
Overview
DS1238AS-5 from Dallas Semiconductor (now Maxim Integrated) is a microprocessor supervisory IC providing power-fail detection, watchdog timer, non-maskable interrupt, and battery-backed SRAM control. It features 4.75 V ±5% VCC trip point, dual active-high/active-low reset outputs, and 200 nA battery current. Used in industrial embedded systems requiring orderly shutdown and data retention during brownouts.
For engineers reviewing the DS1238AS-5 datasheet, DS1238AS-5 pinout, DS1238AS-5 application, or DS1238AS-5 equivalent, key selection criteria include precise 5% power-monitoring threshold, NMI-driven early warning, VCCO-controlled SRAM backup, and pushbutton-debounced reset with watchdog timeout flexibility via OSCSEL/OSCIN.
Technical Context
The DS1238AS-5 integrates a bandgap voltage reference and precision comparator for accurate 5% VCC monitoring (VCCTP = 4.75 V typ), triggering RST/RST and PF outputs on out-of-tolerance conditions. Its internal watchdog timer supports configurable timeout periods (110 ms to 2.7 s) via OSCSEL and OSCIN, with ST input strobing to prevent spurious resets.
It delivers dual-mode memory backup: VCCO switches between VCC and VBAT (≤4.0 V) with diode-drop isolation (VBAT−0.8 V), while CEO provides write-protection timing synchronized to CEI and tCE (5 µs max). The IN pin enables user-defined early-warning thresholds (VTP = 1.27 V) with built-in 3-sample hysteresis to reject noise.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Trip Point | 4.75 V (5% option), ensures reset activation before critical microprocessor undervoltage |
| Battery Current (IBAT) | <200 nA at VBAT = 3.0 V, preserves battery life for years in data-retention mode |
| Reset Pulse Width (tRST) | 40–150 ms, guarantees stable microprocessor initialization after power recovery |
| Watchdog Timeout (Int Clock) | 110 ms (short) / 2.7 s (long), configurable via OSCSEL for software supervision granularity |
| IN Trip Voltage (VTP) | 1.15–1.35 V, enables user-defined early-warning threshold via external resistor divider |
| VCCO Output Range | VCC−0.3 V or VBAT−0.8 V, supplies SRAM with minimal dropout and UL-compliant battery isolation |
| tCE Delay | 5 µs max, defers write protection until current memory cycle completes to prevent data corruption |
Pinout & Package
DS1238AS-5 is available in 16-pin SOIC (300-mil) and 16-pin DIP packages. Both share identical pin mapping and electrical behavior.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VBAT | +3 V Battery Input | Provides backup power for control logic and SRAM when VCC fails; enables nonvolatile operation |
| VCCO | Switched SRAM Supply Output | Delivers regulated power to SRAM from VCC or VBAT (whichever higher), with 0.8 V diode drop for UL compliance |
| VCC | +5 V Primary Power Input | Main system supply; monitored for 5% tolerance violation triggering reset and PF |
| GND | Ground Reference | Common return path for all analog and digital functions; referenced for VCCTP and VTP comparisons |
| PF | Power-Fail Indicator (active high) | Drives external MOSFET or PMIC to switch load from VCC to VBAT during brownout |
| RVT | Reset Voltage Threshold Monitor | Open-drain output indicating VCC < VCCTP; used for system-level power status signaling |
| OSCIN | Oscillator Timing Input/Capacitor Node | Accepts external capacitor (e.g., 47 pF) or clock signal to set watchdog and reset timing |
| OSCSEL | Oscillator Select Control | Configures internal vs. external clock source for watchdog and reset pulse generation |
| IN | Early Warning Input | High-impedance sense node for user-defined voltage threshold (e.g., 4.8 V via R1/R2 divider) |
| NMI | Non-Maskable Interrupt Output | Active-low signal notifying CPU of impending power loss, enabling safe data save before reset |
| ST | Strobe Input | Software-triggered watchdog reset; falling edge resets timeout counter to prevent lockup |
| CEO | Chip Enable Output | Controls SRAM CE pin; held high during VCC fail to enforce write protection after tCE delay |
| CEI | Chip Enable Input | SRAM CE state input; CEO follows CEI during normal operation (20 ns prop delay) |
| WDS | Watchdog Status Output | Latched active-low flag indicating watchdog timeout occurred; cleared by ST strobe or VCC recovery |
| RST | Reset Output (active low) | Primary microprocessor reset signal; asserted for ≥40 ms after VCC crosses VCCTP |
| RST | Reset Output (active high) | Complementary reset signal for systems requiring active-high reset assertion |
Key Features
| Feature | Design Value |
|---|---|
| 5% Precision Power Monitoring | VCCTP = 4.75 V (typ), tighter tolerance than standard 10% parts, reducing false resets in marginal supplies |
| Programmable Watchdog Timeout | Two selectable internal periods (110 ms / 2.7 s) or external clock-driven timing, enabling flexible firmware supervision |
| Early Warning NMI with Hysteresis | IN pin detects user-defined voltage decay with 3-sample time-domain hysteresis (≈100 µs), eliminating noise-induced false interrupts |
| SRAM Write-Protection Timing Control | tCE = 5 µs maximum delay ensures memory cycle completion before CEO forces write protect, preventing data corruption |
| Freshness Seal Function | Electrically isolates VBAT until VCC is applied, preventing unintended SRAM power-up during battery installation |
Applications
| Industrial Data Logger | Medical Diagnostic Device |
|---|---|
Use Scenario: Battery-powered field recorder capturing sensor data during intermittent AC power loss. IC Role / Device Role / Timing Role: DS1238AS-5 monitors VCC, triggers NMI to initiate flash save, then asserts RST after VCCTP breach to halt CPU while CEO write-protects SRAM. Use Value: Guarantees data integrity across >1000 power cycles using <200 nA battery drain and 4.75 V trip accuracy. | Use Scenario: Portable ultrasound unit with volatile buffer memory requiring zero-data-loss shutdown during battery swap. IC Role / Device Role / Timing Role: DS1238AS-5 uses IN pin to detect main DC rail decay at 9.0 V (via R1/R2), issues NMI for buffer flush, then activates PF to switch VCCO to VBAT before VCC drops below 4.75 V. Use Value: Enables seamless battery hot-swap with no interruption to real-time imaging pipeline or SRAM retention. |
| Point-of-Sale Terminal | Smart Energy Meter |
Use Scenario: Retail terminal with EEPROM-backed transaction log that must survive grid flicker events. IC Role / Device Role / Timing Role: DS1238AS-5 debounces mechanical reset button, feeds ST from CPU address bus, and holds CEO high during brownout to freeze EEPROM writes. Use Value: Prevents EEPROM corruption during sub-50 ms dips via 40 µs VCC-fail-to-RST response and tCE-gated write protection. | Use Scenario: Utility meter with tamper-detection circuitry powered by supercapacitor during mains outage. IC Role / Device Role / Timing Role: DS1238AS-5 configures OSCIN/OSCSEL for 110 ms watchdog period, monitors VCC via PF-driven external switch, and asserts RST only after confirmed 3-cycle VCC decay. Use Value: Eliminates false tamper flags during transient sags by combining 5% trip point with 100 µs hysteresis on IN/NMI path. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX691ACPE+ | Pin-compatible but 10% VCC trip (4.5 V), no programmable watchdog timeout; fixed 1.6 s timeout | Lacks NMI early warning and IN pin flexibility; suitable only where 5% precision not required | Select MAX691ACPE+ only if system tolerates wider trip hysteresis and does not require user-defined power-fail warning |
| TPS3823-50DBVR | Single 5.0 V reset threshold (±0.5%), no NMI, no SRAM control outputs (CEO/CEI/VCCO), no watchdog | Basic reset supervisor only; cannot replace DS1238AS-5's memory backup or early-warning functions | Choose TPS3823-50DBVR only for simple reset generation without SRAM management or NMI capability |
Compared with MAX691ACPE+ and TPS3823-50DBVR, DS1238AS-5 uniquely integrates 5% precision monitoring, NMI-driven early warning, and full SRAM backup control-enabling robust data retention in battery-critical applications where partial functionality alternatives would require additional discrete components and PCB area.
Availability
DS1238AS-5 is available at Aetrix Electronics and suitable for industrial data loggers, medical diagnostic devices, point-of-sale terminals, and smart energy meters requiring stable component supply and long-term lifecycle support.
Supply support for DS1238AS-5 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
Dallas Semiconductor, now part of Analog Devices (via Maxim Integrated acquisition), designs high-reliability mixed-signal ICs for power management, timing, and data integrity in harsh environments.
The DS1238A family was engineered specifically for microprocessor-based systems needing coordinated power monitoring, reset control, and nonvolatile memory backup-targeting industrial, medical, and instrumentation applications demanding guaranteed data retention during supply transients.
FAQ
What is the exact VCC trip voltage specification for DS1238AS-5?
The DS1238AS-5 has a guaranteed 5% power supply monitoring threshold: VCCTP = 4.75 V (minimum), 4.62 V (typical), and 4.50 V (maximum) across temperature and process variation. This tighter tolerance versus standard 10% parts (e.g., DS1238A-10) ensures earlier, more reliable reset assertion during marginal 5 V supply decay. The DS1238AS-5 datasheet specifies this value under Recommended DC Operating Conditions and DC Electrical Characteristics tables.
Does DS1238AS-5 support both active-high and active-low reset outputs simultaneously?
Yes, DS1238AS-5 provides two independent reset outputs: RST (active low) and RST (active high), both asserted concurrently when VCC falls below VCCTP. This dual-output architecture eliminates need for external inverters in systems requiring either polarity, simplifying interface to diverse microprocessors and FPGAs. The DS1238AS-5 datasheet confirms simultaneous assertion timing in the AC Electrical Characteristics table (tRPD parameter).
How does the DS1238AS-5 implement early warning power-fail detection?
The DS1238AS-5 uses its IN pin to monitor a user-defined voltage threshold (VTP = 1.27 V nominal) via external resistor divider. When the divided voltage falls below VTP, it triggers NMI after three consecutive 33 µs samples (≈100 µs total), rejecting noise. This gives the host processor time to save critical data before RST assertion. The DS1238AS-5 datasheet details this hysteresis mechanism in the Non-Maskable Interrupt section and Figure 5.
Can DS1238AS-5 directly drive SRAM chip-enable signals without external buffering?
Yes, DS1238AS-5's CEO output drives SRAM CE pins directly: it sources/sinks ≥4 mA (IOL/IOH specs), has 20 ns propagation delay, and supports 5 µs minimum pulse width (tCE). During VCC failure, CEO transitions to high-impedance or active-high state per CEI state and tCF timing (7–144 µs), ensuring clean write protection. The DS1238AS-5 datasheet validates this in DC/AC Electrical Characteristics and Memory Backup sections.
What is the maximum battery voltage supported at the VBAT pin of DS1238AS-5?
The DS1238AS-5 specifies an absolute maximum VBAT rating of +4.0 V, with recommended operating range of 0 V to 4.0 V. Exceeding 4.0 V risks damage to internal protection circuitry. In battery-backup mode, VCCO delivers VBAT−0.8 V to SRAM, making 3.0 V lithium or coin cells ideal. This limit is explicitly stated in the Absolute Maximum Ratings table of the DS1238AS-5 datasheet.
DS1238AS-5 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- MicroManager
- Package/Case:
- 16-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Type:
- Battery Backup Circuit
- Number of Voltages Monitored:
- 1
- Voltage - Threshold:
- 4.62V
- Output:
- Open Drain or Open Collector
- Reset:
- Active High/Active Low
- Reset Timeout:
- 40ms Minimum
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
DS1238AS-5 FAQ
1.How can I place an order for DS1238AS-5 through Aetrix?
Please submit a Request for Quotation (RFQ) for DS1238AS-5 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for DS1238AS-5 reliable?
The price and inventory of DS1238AS-5 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for DS1238AS-5 is usually 5 days.
3.What payment methods are accepted for DS1238AS-5?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for DS1238AS-5 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for DS1238AS-5?
DS1238AS-5 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your DS1238AS-5 order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for DS1238AS-5?
For technical support, including DS1238AS-5 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your DS1238AS-5 requirements.
6.How does Aetrix verify that DS1238AS-5 is sourced from the original manufacturer or authorized distributors?
All DS1238AS-5 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that DS1238AS-5 meets industry standards.
7.What is the process for return or replacement of DS1238AS-5?
All DS1238AS-5 units undergo pre-shipment inspection (PSI). If there is an issue with DS1238AS-5, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The DS1238AS-5 part is unused and in its original packaging.
Return procedure for DS1238AS-5:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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