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Analog Devices Inc./Maxim Integrated DS1238AS-10
- Part No.:
- DS1238AS-10
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- 16-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
DS1238AS-10.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:300
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Product details
Overview
DS1238AS-10 from Dallas Semiconductor (now Maxim Integrated) is a microprocessor supervisory IC providing power-fail detection, watchdog timer, non-maskable interrupt, battery-backed SRAM control, and dual active-low/active-high reset outputs. It monitors +5V supply with 10% trip point (4.25–4.50 V), consumes <200 nA battery current, and supports 16-pin SOIC/DIP packaging. Used in industrial embedded systems requiring orderly shutdown and data retention during brownouts.
For engineers reviewing the DS1238AS-10 datasheet, DS1238AS-10 pinout, DS1238AS-10 application, or DS1238AS-10 equivalent, key selection considerations include its 4.37 V typical VCCTP, 2.7 s internal watchdog timeout, VCCO output for SRAM backup, RVT threshold indicator, and PF-driven external power switching capability.
Technical Context
The DS1238AS-10 integrates a bandgap voltage reference and precision comparator to monitor VCC against a 4.37 V typical trip point, asserting RST/RST and RVT within 100 µs of out-of-tolerance detection. Its early-warning NMI circuit samples the IN pin at ~30 kHz with triple-sampling hysteresis to reject noise.
A programmable watchdog timer uses either internal oscillator (2.7 s long period) or external clock/capacitor timing; ST input must be strobed low before timeout to prevent reset. OSCSEL and OSCIN configure timing source, while CEO provides controlled chip-enable gating for SRAM write protection with tCE = 5 µs delay.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Power Supply Trip Point | 4.25–4.50 V (10% tolerance); ensures reset activation before microprocessor instability at VCC < 4.5 V |
| Battery Current (IBAT) | <200 nA at VBAT = 3.0 V; enables multi-year SRAM data retention on coin cell |
| Reset Pulse Width (tRST) | 40–150 ms (typ 85 ms); meets minimum reset hold time for 8051, Z80, and 68K-family processors |
| Watchdog Timeout (Int. Clock) | 1.7–2.7 s (typ 2.7 s); provides sufficient software recovery window before forced reset |
| VCCO Output Capability | 100 mA at VCC−0.3 V; powers standard 32k×8 or 64k×8 CMOS SRAM during main supply loss |
| NMI Response Delay (tIPD) | 40–175 µs; delivers early warning ≥100 µs before RST assertion for controlled save operations |
| CEO Propagation Delay | 20 ns; guarantees synchronous write-protection enable relative to CEI signal edge |
Pinout & Package
DS1238AS-10 is available in 16-pin SOIC (300-mil) and 16-pin DIP packages. Both variants share identical pin mapping and thermal characteristics, rated for commercial temperature range (0°C to +70°C).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VBAT | +3 V battery input | Provides backup power path; disconnects via freshness seal until VCC applied |
| VCCO | Switched SRAM supply output | Auto-selects higher of VCC or VBAT−0.8 V; supplies up to 100 mA to SRAM |
| VCC | +5 V primary supply input | Monitored supply rail; trip point set to 4.37 V typical for 10% tolerance |
| GND | Ground reference | Common return for all analog/digital circuits; referenced for all voltage thresholds |
| PF | Power-fail indicator (active high) | Drives external MOSFET/switch to transition load from VCC to VBAT at VCC ≈ VBAT |
| RVT | Reset voltage threshold indicator | Open-drain output active when VCC < VCCTP; used for system-level voltage status monitoring |
| OSCIN | Oscillator timing input | Accepts external clock or 47 pF capacitor for programmable watchdog/reset timing |
| OSCSEL | Oscillator select | Hi/Open = internal 2.7 s timer; Low = external clock/capacitor mode |
| IN | Early-warning sense input | High-impedance (±1 µA) node for resistor-divider setup; VTP = 1.27 V typical |
| NMI | Non-maskable interrupt output | Active-low signal triggered when IN falls below VTP; includes 100 µs noise immunity |
| ST | Watchdog strobe input | Falling edge resets watchdog timer; open = watchdog disabled |
| CEO | Chip enable output | Drives SRAM CE; held high during power fail to unconditionally write-protect memory |
| CEI | Chip enable input | Controls CEO pass-through; write protection delayed until CEI returns high or tCE expires |
| WDS | Watchdog status output | Latched active-low flag indicating timeout occurred; cleared by ST strobe or VCC recovery |
| RST | Reset output (active low) | Guaranteed 50 ms min active pulse after VCC rises above VCCTP; drives µP /RESET |
| RST | Reset output (active high) | Complementary to active-low RST; used where logic-high reset is required |
Key Features
| Feature | Design Value |
|---|---|
| Unconditional SRAM write protection | CEO forced high within 144 µs of VCC falling below VCCTP, preventing data corruption during power loss |
| Programmable watchdog timer | Configurable via OSCSEL/OSCIN for 2.7 s internal or capacitor-based timeout; ST strobe resets counter |
| Dual-reset outputs | Simultaneous active-low and active-high RST signals eliminate need for external inverters in mixed-logic systems |
| Freshness seal function | Electrically isolates VBAT until VCC is applied, preventing premature battery discharge during assembly |
| PF-driven external power switching | PF output switches load between VCC and VBAT at VCC ≈ VBAT, enabling high-current backup without internal FET limits |
Applications
| Industrial Data Logger | Point-of-Sale Terminal |
|---|---|
|
Use Scenario: Battery-backed data logger records sensor readings during AC mains failure. IC Role / Device Role / Timing Role: DS1238AS-10 detects VCC decay, asserts NMI to trigger immediate RAM save, then asserts RST after safe storage. Use Value: 100 µs NMI latency and 20 ns CEO propagation ensure no sample is lost during brownout transition. |
Use Scenario: POS terminal retains transaction buffer and configuration during brief power interruption. IC Role / Device Role / Timing Role: DS1238AS-10 gates SRAM CE via CEO and holds VCCO stable using VBAT, preserving volatile session data. Use Value: 100 mA VCCO drive and <200 nA IBAT support 10+ year coin-cell life with full 64k×8 SRAM retention. |
| Medical Diagnostic Equipment | Telecom Line Card |
|
Use Scenario: Ultrasound machine saves calibration parameters and last image frame before shutdown. IC Role / Device Role / Timing Role: DS1238AS-10 uses IN pin to monitor intermediate 12 V rail, issuing NMI earlier than main 5 V rail collapse. Use Value: Configurable IN threshold (via R1/R2 divider) enables earliest possible warning from highest system voltage node. |
Use Scenario: Carrier-grade line card maintains register state and alarm history during hot-swap power blip. IC Role / Device Role / Timing Role: DS1238AS-10's PF output controls external ideal diode controller, ensuring seamless VCC/VBAT switchover. Use Value: PF transition at VCC ≈ VBAT eliminates voltage glitch and prevents brownout-induced packet loss. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX691CPD+ | Pin-compatible; same 10% VCCTP (4.25–4.50 V), but lacks IN/NMI input and uses fixed 1.6 s watchdog | No early-warning interrupt; requires external circuitry for NMI-equivalent functionality | Select MAX691CPD+ only if NMI is unnecessary and footprint compatibility is critical |
| TPS3823-50DBVR | Single-supply supervisor with 5.0 V ±2% threshold (4.9–5.1 V); no VCCO output, no watchdog, no NMI | Only provides reset and power-fail flag; cannot back up SRAM or replace DS1238AS-10's integrated functions | Choose TPS3823-50DBVR only for basic reset-only use cases where SRAM backup and watchdog are handled separately |
Compared with MAX691CPD+ and TPS3823-50DBVR, the DS1238AS-10 uniquely integrates SRAM power switching (VCCO), early-warning NMI, and programmable watchdog in one 16-pin package-enabling compact, single-chip power management for legacy microprocessor systems.
Availability
DS1238AS-10 is available at Aetrix Electronics and suitable for industrial data loggers, point-of-sale terminals, medical diagnostic equipment, and telecom line cards requiring stable component supply and long-term obsolescence support.
Supply support for DS1238AS-10 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), pioneered real-time clocks, battery-backed RAM supervisors, and secure authentication ICs for industrial and embedded markets.
The DS1238A family was designed specifically for microprocessor-based systems needing coordinated power monitoring, reset control, and nonvolatile SRAM backup-targeting applications where firmware-controlled shutdown and data integrity are mission-critical.
FAQ
What is the exact power supply trip point for DS1238AS-10?
The DS1238AS-10 has a guaranteed 10% power supply monitoring threshold, with VCCTP specified from 4.25 V to 4.50 V (typical 4.37 V) at 0°C to +70°C. This ensures reliable reset assertion before most 5 V microprocessors enter undefined operation, and differs from the 5% option (DS1238A-5) which trips at 4.75 V.
Does DS1238AS-10 support both active-low and active-high reset outputs simultaneously?
Yes, DS1238AS-10 provides two dedicated RST pins: one active-low and one active-high, both asserted concurrently during power failure or watchdog timeout. This eliminates external level-shifting components in systems requiring mixed logic families or legacy processor interfaces that demand specific reset polarity.
How does the DS1238AS-10 prevent false NMI triggers from power supply noise?
The DS1238AS-10 implements time-domain hysteresis on the IN pin: it samples the voltage every ~33 µs using an internal ring oscillator and requires three consecutive out-of-tolerance readings (≈100 µs total) before asserting NMI. This design rejects transient spikes while preserving response to genuine slow-decay brownouts.
Can DS1238AS-10 directly power a 64k×8 SRAM during main supply loss?
Yes, DS1238AS-10's VCCO output delivers up to 100 mA at VCC−0.3 V during normal operation and sustains SRAM with VBAT−0.8 V during backup, meeting the current requirements of standard 64k×8 CMOS SRAMs. Its CEO output also enforces write protection within 144 µs of VCC decay to prevent data corruption.
Is the DS1238AS-10 pinout compatible with MAX691, and what are the functional limitations?
DS1238AS-10 is pin-for-pin compatible with MAX691 in 16-pin DIP/SOIC packages, sharing identical VCC, GND, RST, PF, and CEI/CEO pin assignments. However, DS1238AS-10 adds IN, NMI, WDS, OSCIN, OSCSEL, and RVT pins-functions absent in MAX691-so full feature parity requires board-level redesign beyond footprint reuse.
DS1238AS-10 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:
- 4.37V
- 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-10 FAQ
1.How can I place an order for DS1238AS-10 through Aetrix?
Please submit a Request for Quotation (RFQ) for DS1238AS-10 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-10 reliable?
The price and inventory of DS1238AS-10 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for DS1238AS-10 is usually 5 days.
3.What payment methods are accepted for DS1238AS-10?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for DS1238AS-10 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for DS1238AS-10?
DS1238AS-10 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your DS1238AS-10 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-10?
For technical support, including DS1238AS-10 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your DS1238AS-10 requirements.
6.How does Aetrix verify that DS1238AS-10 is sourced from the original manufacturer or authorized distributors?
All DS1238AS-10 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-10 meets industry standards.
7.What is the process for return or replacement of DS1238AS-10?
All DS1238AS-10 units undergo pre-shipment inspection (PSI). If there is an issue with DS1238AS-10, 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-10 part is unused and in its original packaging.
Return procedure for DS1238AS-10:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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