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Analog Devices Inc./Maxim Integrated DS1238-5+
- Part No.:
- DS1238-5+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Supervisors
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
DS1238-5+.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL 16DIP
- Quantity:
- Payment:
- Shipping:
Inventory:559
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Product details
Overview
DS1238-5+ from Maxim Integrated (now part of Analog Devices) is a microprocessor supervisory IC providing power-fail detection, watchdog reset control, non-maskable interrupt generation, SRAM backup switching, and battery-freshness sealing in embedded systems. It features 4.75 V ±5% VCC trip point, dual active-high/active-low RST outputs, 200 nA battery current, and supports 16-pin DIP/SOIC packages.
For engineers reviewing the DS1238-5+ datasheet, DS1238-5+ pinout, DS1238-5+ application, or DS1238-5+ equivalent, key selection criteria include precise 5% supply monitoring threshold, NMI-driven early warning shutdown, VCCO-controlled SRAM backup, and watchdog timeout configurability via OSCSEL/OSCIN.
Technical Context
The DS1238-5+ integrates a bandgap voltage reference and precision comparator for 4.75 V (typ. 4.62 V) VCC trip detection, with hysteresis and 100 µs noise immunity via triple-sampling. Its watchdog timer supports internal (2.7 s / 170 ms) or external clock sources, resettable via ST strobe input.
It implements dual-path memory protection: CEO output unconditionally write-protects SRAM when VCC falls below VCCTP, with tCE = 5 µs delay to complete current cycle; VCCO switches between VCC and VBAT (2.7–4.0 V) with diode-drop isolation (VBAT − 0.8 V) to prevent battery charging.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Trip Point | 4.75 V (min), 4.62 V (typ), 4.50 V (max) - enables precise 5% tolerance monitoring per DS1238-5 designation |
| Battery Current (IBAT) | <200 nA at VBAT = 3.0 V - ensures multi-year SRAM data retention on coin cell |
| Reset Pulse Width (tRST) | 40–150 ms - guarantees microprocessor stabilization after power-up or brownout |
| Watchdog Timeout (Internal) | 1.7–2.7 s (long), 110–170 ms (short) - configurable via OSCSEL for fail-safe software supervision |
| NMI Response Delay (tIPD) | 40–175 µs - delivers deterministic early-warning interrupt before VCC collapse |
| VCCO Output Voltage | VCC − 0.3 V (normal), VBAT − 0.8 V (battery mode) - maintains SRAM VDD within JEDEC-compliant margins |
| CEO Propagation Delay | 20 ns - enables cycle-accurate SRAM write-protection activation |
Pinout & Package
DS1238-5+ is available in 16-pin plastic DIP (300-mil) and 16-pin SOIC (300-mil) packages. Both share identical pinout and thermal characteristics.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VBAT | +3 V Battery Input | Primary source for nonvolatile operation; powers internal logic and VCCO during VCC loss |
| VCCO | Switched SRAM Supply Output | Auto-selects higher of VCC or VBAT (with 0.8 V diode drop) to sustain SRAM during power failure |
| VCC | +5 V Power Supply Input | Main system supply; monitored for 4.75 V trip point; powers all active circuitry |
| GND | Ground Reference | Common return for analog/digital sections; referenced for all voltage thresholds |
| PF | Power-Fail Indicator (Active High) | Drives external MOSFET/switch to transfer load from VCC to VBAT; remains active during VCC < VBAT |
| 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/reset timing |
| OSCSEL | Oscillator Select Control | Hi/Open = internal oscillator; Low = external clock/capacitor - configures timeout periods |
| IN | Early Warning Sense Input | High-impedance comparator input (VTP = 1.27 V); accepts resistor-divider for custom voltage monitoring |
| NMI | Non-Maskable Interrupt Output | Active-low interrupt triggered when IN falls below VTP; provides ≥100 µs warning before RST assertion |
| ST | Watchdog Strobe Input | Falling edge resets watchdog timer; must occur before timeout to prevent forced reset |
| CEO | Chip Enable Output | Write-protects SRAM by forcing CE high when VCC fails; delays tCE = 5 µs to avoid mid-cycle corruption |
| CEI | Chip Enable Input | Controls CEO state during normal operation; CEO follows CEI with 20 ns propagation 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) | Drives microprocessor /RESET pin; asserted for ≥40 ms after VCC rises above VCCTP |
| RST | Reset Output (Active High) | Complementary active-high reset signal for logic-level interface or FPGA configuration |
Key Features
| Feature | Design Value |
|---|---|
| 5% Precision Power Monitoring | DS1238-5+ variant guarantees VCCTP = 4.75 V (min), enabling tighter supply margining than standard 10% parts |
| Early Warning NMI with Hysteresis | Triple-sampled 100 µs noise immunity prevents false interrupts; gives deterministic time to save critical data |
| SRAM Write-Protection Timing Control | tCE = 5 µs delay ensures CEO asserts only after current memory cycle completes - eliminates data corruption risk |
| Freshness Seal Function | Three negative pulses on IN during +5 V operation tri-states VCCO/RST/CEO and latches WDS low - preserves battery during shipment |
| Configurable Watchdog Timeout | OSCSEL/OSCIN allow selection between 2.7 s (long) and 170 ms (short) timeouts - matches software loop timing requirements |
Applications
| Industrial Data Logger | Medical Diagnostic Device |
|---|---|
Use Scenario: Battery-backed data acquisition unit logging sensor readings during AC mains outage. IC Role / Device Role / Timing Role: DS1238-5+ monitors 5 V rail, triggers NMI at 4.8 V to initiate flash save, then asserts RST at 4.75 V while CEO write-protects SRAM. Use Value: Guarantees ≥100 µs warning window and <5 µs write-protection delay - preserves last valid measurement before power collapse. | Use Scenario: Portable ultrasound machine requiring zero-data-loss shutdown during battery swap. IC Role / Device Role / Timing Role: DS1238-5+ uses VBAT = 3.3 V to sustain SRAM and VCCO during hot-swap; PF drives external switch to isolate main supply. Use Value: VCCO = VBAT − 0.8 V ensures SRAM VDD stays >2.5 V - meets JEDEC JESD79-3 DDR2 retention spec under battery-only operation. |
| Point-of-Sale Terminal | Smart Energy Meter |
Use Scenario: Retail terminal performing secure transaction commit before grid failure. IC Role / Device Role / Timing Role: DS1238-5+ detects 5 V sag via IN pin tied to 12 V DC bus (via R1/R2 divider); NMI initiates crypto key flush to EEPROM. Use Value: Custom IN threshold (e.g., 9.0 V) extends warning time by 2× vs. VCC monitoring alone - enables full AES-256 encryption before RST. | Use Scenario: Utility meter retaining tamper logs and billing cycles during brownouts. IC Role / Device Role / Timing Role: DS1238-5+ freshness seal activated pre-shipment disables VCCO/RST/CEO; reactivation occurs only after first VCC power cycle. Use Value: Reduces shelf-life battery drain to <200 nA - extends 10-year meter warranty without battery replacement. |
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 but 10% VCC trip (4.5 V), no freshness seal, no IN/NMI early warning path | Lacks deterministic pre-reset warning; requires external circuitry for SRAM backup sequencing | Select MAX691CPD+ only if 10% tolerance suffices and NMI functionality is unused |
| TPS3823-50DBVR | Single 5 V reset IC with 5% threshold; no watchdog, no NMI, no SRAM switching, no battery support | Provides basic reset only; cannot replace DS1238-5+ in battery-backed nonvolatile memory systems | Choose TPS3823-50DBVR for cost-sensitive, non-battery applications needing only reset assertion |
Compared with MAX691CPD+, DS1238-5+ adds NMI-based early warning, freshness seal, and integrated SRAM backup control - essential for data-critical embedded systems. Versus TPS3823-50DBVR, DS1238-5+ delivers full supervisory functionality including watchdog, battery management, and dual-reset outputs - making it irreplaceable in nonvolatile memory retention designs.
Availability
DS1238-5+ 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 across extended temperature ranges and long product lifecycles.
Supply support for DS1238-5+ 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
Analog Devices (via acquisition of Maxim Integrated) designs high-reliability analog, mixed-signal, and power management ICs for demanding industrial, automotive, and medical applications.
The DS1238-5+ belongs to Maxim's MicroManager family - engineered specifically for robust power supervision, nonvolatile memory backup, and fail-safe microprocessor reset in mission-critical embedded systems.
FAQ
What is the exact VCC trip voltage specification for DS1238-5+?
The DS1238-5+ has a guaranteed VCC trip point of 4.75 V (minimum), 4.62 V (typical), and 4.50 V (maximum) - meeting the 5% tolerance requirement denoted by the "-5" suffix. This is confirmed in the Recommended DC Operating Conditions table and distinguishes it from the standard DS1238 (10% trip at 4.5 V). The DS1238-5+ achieves this using a precision bandgap reference and comparator with built-in hysteresis.
Does DS1238-5+ support both active-high and active-low reset outputs simultaneously?
Yes, DS1238-5+ provides two independent reset outputs: RST (active low) and RST (active high), both asserted synchronously when VCC falls below the 4.75 V trip point. The active-high RST is not an inverted version of RST but a dedicated open-drain output referenced to VCC, enabling direct interface with logic families requiring high-true reset signals without external inverters.
How does the DS1238-5+ implement early warning power-fail detection?
The DS1238-5+ uses its IN pin - a high-impedance input referenced to an internal 1.27 V bandgap - to monitor a user-defined voltage point via external resistor divider. When the divided voltage falls below 1.27 V, the NMI output asserts after three consecutive 33 µs samplings (≈100 µs total), providing deterministic early warning before VCC collapse. This function is fully independent of the main VCC monitor and is central to the DS1238-5+'s role in orderly shutdown.
Can DS1238-5+ be used to back up SRAM without external components?
Yes, DS1238-5+ integrates all necessary functions for SRAM backup: VCCO automatically selects the higher of VCC or VBAT (with 0.8 V diode drop), CEO unconditionally write-protects SRAM upon VCC failure with 5 µs delay (tCE) to complete the current cycle, and the freshness seal prevents battery drain during storage. No external FETs, diodes, or logic are required for basic nonvolatile SRAM operation - only VBAT, VCC, GND, CEI, and CEO connections.
What is the purpose and activation method of the DS1238-5+ freshness seal?
The DS1238-5+ freshness seal electrically disconnects the battery during storage to preserve capacity. It is activated by applying three precisely timed negative pulses (−3 V, 100 ns wide, 1 µs apart) to the IN pin while VCC is at +5 V. Once set, VCCO, RST, RST, and CEO enter high-impedance state and WDS goes low. Normal operation resumes only after cycling VCC above VBAT - ensuring zero battery drain until first power-up.
DS1238-5+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- MicroManager
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Type:
- Battery Backup Circuit
- Number of Voltages Monitored:
- 1
- Voltage - Threshold:
- 4.62V
- Output:
- Open Drain, Push-Pull
- Reset:
- Active High/Active Low
- Reset Timeout:
- 40ms Minimum
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-PDIP
DS1238-5+ FAQ
1.How can I place an order for DS1238-5+ through Aetrix?
Please submit a Request for Quotation (RFQ) for DS1238-5+ 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 DS1238-5+ reliable?
The price and inventory of DS1238-5+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for DS1238-5+ is usually 5 days.
3.What payment methods are accepted for DS1238-5+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for DS1238-5+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for DS1238-5+?
DS1238-5+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your DS1238-5+ 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 DS1238-5+?
For technical support, including DS1238-5+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your DS1238-5+ requirements.
6.How does Aetrix verify that DS1238-5+ is sourced from the original manufacturer or authorized distributors?
All DS1238-5+ 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 DS1238-5+ meets industry standards.
7.What is the process for return or replacement of DS1238-5+?
All DS1238-5+ units undergo pre-shipment inspection (PSI). If there is an issue with DS1238-5+, 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 DS1238-5+ part is unused and in its original packaging.
Return procedure for DS1238-5+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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