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Analog Devices Inc. LTC1235CSW#TRPBF
- Part No.:
- LTC1235CSW#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Supervisors
- Package:
- 16-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
LTC1235CSW#TRPBF.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,100
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Product details
Overview
LTC1235CSW#TRPBF from Analog Devices (acquired Linear Technology) is a microprocessor supervisory circuit integrating power monitoring, conditional battery backup, RAM write protection, power-fail warning, and watchdog timing. It guarantees reset assertion down to VCC = 1V, provides 4.65V precision voltage monitoring with 40mV hysteresis, delivers up to 50mA from VOUT via charge-pumped NMOS switch, and supports programmable battery backup activation via the BACKUP pin. It is used in battery-powered computers and controllers requiring reliable data retention during brownouts.
For engineers reviewing the LTC1235CSW#TRPBF datasheet, LTC1235CSW#TRPBF pinout, LTC1235CSW#TRPBF application, or LTC1235CSW#TRPBF equivalent, key selection criteria include guaranteed reset at 1V VCC, conditional battery backup logic, 35ns max CE propagation delay, 200ms reset timeout, and 1μA standby current - all critical for low-power, fail-safe embedded systems.
Technical Context
The LTC1235CSW#TRPBF implements a multi-function supervisory architecture with three independent comparators (C1 for VCC monitoring, C2 for battery switchover, C3 for power-fail detection), a latched memory logic block that captures the BACKUP pin state during VCC fall-through the 4.65V threshold, and a charge-pumped NMOS power switch (M1) for VOUT with 5Ω typical on-resistance. Its reset pulse generator enforces ≥140ms active-low RESET duration after power-up, push-button release, or watchdog timeout.
It integrates a debounced push-button reset input (PB RST) with ≥40ms low-time requirement, a three-level watchdog input (WDI) with 1.0–2.25s timeout range, and a conditional battery backup control path where the latched BACKUP logic level determines whether M2 (125Ω PMOS) connects VBATT to VOUT when VCC drops below VBATT. The device operates across 0°C to 70°C and features thermal limiting with ~155°C shutdown threshold.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reset Voltage Threshold | 4.65V typical; ensures reliable μP reset before VCC falls below 4.75V (5% tolerance), with 40mV hysteresis to reject supply glitches. |
| VOUT Output Current | 50mA max; sufficient to power CMOS RAM during main supply failure, enabled only when BACKUP = high and VCC < VBATT. |
| Standby Supply Current | 1μA maximum; enables ultra-low-power operation in battery-saving mode when RAM backup is disabled. |
| RESET Active Time | 200ms nominal; provides stable reset hold time for microprocessor initialization and power stabilization. |
| CE Propagation Delay | 35ns max; ensures fast, glitch-free gating of RAM chip enable signals during VCC transitions. |
| Battery Switchover Threshold | 70mV (power-up), 50mV (power-down); defines precise VCC–VBATT differential for seamless backup activation/deactivation. |
| Watchdog Timeout Period | 1.0–2.25s; configurable via external timing components to match system software execution cycles. |
Pinout & Package
Package: 16-Lead Plastic SOIC (SW), RoHS-compliant, 0°C to 70°C operating range.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 VBATT | Backup battery input | Accepts 2.0V–4.25V auxiliary supply; source for VOUT during backup mode when BACKUP = high and VCC < VBATT. |
| 2 VOUT | Backed-up memory output | Delivers up to 50mA to RAM; internally switched between VCC (via M1) and VBATT (via M2) based on BACKUP latch and VCC/VBATT comparison. |
| 3 VCC | +5V main supply input | Primary power source; monitored for reset generation, CE gating, and internal bias; requires 0.1μF bypass capacitor. |
| 4 GND | Ground reference | Common return for all analog and digital functions; must be low-impedance connection to minimize noise coupling. |
| 5 BATT ON | Battery-on logic output | Open-drain output indicating VOUT sourcing from VCC (low) or VBATT (high); can drive external PNP transistor for >50mA loads. |
| 6 LOW LINE | Low-line indicator output | Active-low signal asserting when VCC falls below 4.65V; used for early power-fail notification independent of RESET timing. |
| 7 PB RST | Debounced push-button input | Active-low, ≥40ms debounced reset trigger; initiates ≥140ms RESET pulse upon release, eliminating mechanical bounce issues. |
| 8 BACKUP | Conditional backup control input | Latched during VCC fall-through reset threshold; high = enable battery backup, low = disable (battery saving mode). |
| 9 PFI | Power-fail comparator input | Non-inverting input referenced to 1.3V internal bandgap; used with external divider to generate early PFO warning before VCC reaches reset threshold. |
| 10 PFO | Power-fail output | Active-low open-drain output signaling PFI < 1.3V; forces low when VCC < VBATT, enabling safe shutdown sequencing. |
| 11 WDI | Watchdog timer input | Three-level input (high/low/floating); toggling required within timeout period to prevent RESET/WDO assertion; floating disables watchdog. |
| 12 CE OUT | Gated chip-enable output | Buffered replica of CE IN when VCC > reset threshold; forced high during brownout to write-protect RAM regardless of CE IN state. |
| 13 CE IN | Chip-enable input | Accepts microprocessor address decoder or CS signal; propagation delay ≤35ns ensures synchronous memory protection. |
| 14 WDO | Watchdog logic output | Active-low output mirroring RESET behavior during watchdog timeout; resets high on WDI transition or LOW LINE assertion. |
| 15 RESET | Active-low reset output | Guaranteed logic low down to VCC = 1V; drives μP reset pin directly; remains active ≥140ms after VCC recovery or PB RST release. |
| 16 RESET | Active-high reset output | Inverse of pin 15; provides complementary reset signal for systems requiring active-high assertion. |
Key Features
| Feature | Design Value |
|---|---|
| Guaranteed reset at VCC = 1V | Ensures microprocessor remains held in reset during deep brownouts, preventing undefined execution and data corruption. |
| Conditional battery backup | Extends battery life by disabling VOUT-to-VBATT switching when RAM data persistence is unnecessary (e.g., long-term storage). |
| Fast 35ns CE gating | Prevents spurious writes to backed-up RAM during power transitions, meeting tight timing requirements of high-speed CMOS memory. |
| 1.5mA max supply current | Minimizes loading on primary 5V rail during normal operation while maintaining full supervisory functionality. |
| Integrated power-fail warning (PFI/PFO) | Enables μP-initiated graceful shutdown before reset occurs, preserving volatile state and logging critical events. |
| Thermal limiting with shutdown | Protects against sustained overload by disabling VOUT switch at ~155°C, preventing damage during short-circuit or overcurrent conditions. |
Applications
| Battery-Powered Computers | Intelligent Instruments |
|---|---|
Use Scenario: Portable data loggers powered by Li-ion batteries experience intermittent AC adapter disconnection and voltage sag during field operation. IC Role / Device Role / Timing Role: LTC1235CSW#TRPBF monitors VCC, asserts RESET if voltage drops below 4.65V, and conditionally activates VBATT to VOUT only when sensor data must be preserved. Use Value: Prevents data loss during brief outages while extending battery life by disabling backup when no critical writes are pending. |
Use Scenario: Handheld multimeters with nonvolatile RAM store calibration coefficients and user settings across power cycles. IC Role / Device Role / Timing Role: LTC1235CSW#TRPBF gates CE IN to CE OUT, forcing RAM write-protection during brownout, and uses PFO to trigger EEPROM save before RESET. Use Value: Guarantees RAM integrity and enables deterministic firmware-controlled parameter backup prior to power collapse. |
| Automotive Systems | Critical μP Power Monitoring |
Use Scenario: Infotainment head units endure wide input voltage swings (6V–16V) during engine cranking and load dump events. IC Role / Device Role / Timing Role: LTC1235CSW#TRPBF uses external resistor divider on PFI to detect pre-failure voltage drop, generating PFO interrupt for controlled UI shutdown before VCC crosses 4.65V. Use Value: Avoids display artifacts and file system corruption by initiating graceful power-down sequence ahead of hard reset. |
Use Scenario: Industrial PLC controllers require deterministic reset behavior under noisy 24VDC supply with ripple and transients. IC Role / Device Role / Timing Role: LTC1235CSW#TRPBF provides 200ms reset timeout with 40mV hysteresis on VCC monitor, and debounced PB RST for manual recovery without external RC networks. Use Value: Eliminates need for discrete reset ICs and debounce circuits, reducing BOM count and board space while improving reliability. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar microprocessor supervisory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX692AESA+ | Single 4.65V reset threshold; no conditional battery backup, no CE gating, no PFI/PFO comparator; 12μA quiescent current. | Suitable only for basic reset generation - lacks RAM protection, power-fail warning, and battery management features. | Select when only reset supervision is needed and cost is prioritized over feature set. |
| TPS3823DBVR | Fixed 200ms reset timeout; no battery backup, no CE output, no watchdog; 15μA supply current; supports 3.0V/3.3V/5.0V thresholds. | Designed for general-purpose reset IC use; cannot interface with RAM or manage auxiliary power paths. | Choose for simple, low-cost reset-only applications where VCC monitoring suffices and battery extension is irrelevant. |
Compared with MAX692AESA+ and TPS3823DBVR, the LTC1235CSW#TRPBF uniquely integrates conditional battery backup, CE gating, and dual-comparator power-fail warning - making it irreplaceable in systems requiring coordinated memory protection and intelligent power management during brownout.
Availability
LTC1235CSW#TRPBF is available at Aetrix Electronics and suitable for battery-powered computers, intelligent instruments, automotive systems, and critical μP power monitoring applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LTC1235CSW#TRPBF 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 acquired Linear Technology in 2017 and maintains its legacy precision analog and power management product lines, including supervisory ICs designed for high-reliability embedded systems.
The LTC1235CSW#TRPBF belongs to Linear's μP supervisory family, engineered specifically for systems requiring coordinated reset, memory protection, battery backup control, and early power-fail detection in space-constrained, low-power environments.
FAQ
What is the guaranteed minimum VCC voltage at which LTC1235CSW#TRPBF asserts RESET?
The LTC1235CSW#TRPBF guarantees RESET remains active low down to VCC = 1V, ensuring the microprocessor stays in a known reset state even during severe brownouts. This specification is verified across temperature and process corners, and is critical for maintaining system integrity when primary supply collapses gradually. The LTC1235CSW#TRPBF achieves this using a dedicated low-voltage reset detection circuit independent of the main bandgap reference.
How does the conditional battery backup function work in LTC1235CSW#TRPBF?
The LTC1235CSW#TRPBF samples the logic level on the BACKUP pin as VCC falls through the 4.65V reset threshold and latches that state. If latched high, it enables the internal 125Ω PMOS switch (M2) to connect VBATT to VOUT when VCC drops below VBATT; if latched low, it disables M2 and places VOUT in Battery Saving Mode. This extends battery life by avoiding unnecessary discharge when RAM data persistence is not required - a capability absent in most supervisory ICs. The LTC1235CSW#TRPBF implements this entirely on-chip without external logic.
What is the purpose of the CE IN and CE OUT pins on LTC1235CSW#TRPBF?
The CE IN and CE OUT pins provide hardware-enforced write protection for battery-backed CMOS RAM. When VCC is valid (>4.65V), CE OUT replicates CE IN with ≤35ns propagation delay. When VCC falls below the reset threshold or VBATT, CE OUT is forced high - overriding CE IN - to disable RAM writes and prevent data corruption. This gating is synchronized to the reset event and eliminates reliance on firmware-based protection. The LTC1235CSW#TRPBF uses this feature to ensure memory integrity during power transitions.
Can LTC1235CSW#TRPBF generate an early warning before system reset occurs?
Yes. The LTC1235CSW#TRPBF includes a dedicated power-fail comparator (C3) with PFI input referenced to an internal 1.3V bandgap. By connecting PFI to a resistor divider from VCC, designers can set PFO to assert several milliseconds before VCC reaches the 4.65V reset threshold. This gives the microprocessor time to execute shutdown routines, save state, or log events before RESET is asserted. The LTC1235CSW#TRPBF supports this function without additional components and maintains PFO low when VCC < VBATT.
What is the maximum continuous output current from VOUT on LTC1235CSW#TRPBF?
The LTC1235CSW#TRPBF delivers up to 50mA continuously from the VOUT pin when powered from VCC via its internal charge-pumped NMOS switch (M1), with a typical on-resistance of 5Ω. During battery backup mode, VOUT sourcing from VBATT is limited by M2's 125Ω resistance and thermal constraints - sustaining >250μA requires careful thermal design. For higher currents, the BATT ON output can drive an external PNP transistor. The LTC1235CSW#TRPBF includes short-circuit protection and thermal shutdown to safeguard against overload.
LTC1235CSW#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Programmable:
- Not Verified
- Type:
- Simple Reset/Power-On Reset
- Number of Voltages Monitored:
- 1
- Voltage - Threshold:
- 4.65V
- Output:
- Open Drain, Open Drain
- Reset:
- Active High/Active Low
- Reset Timeout:
- 140ms Minimum
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SO
LTC1235CSW#TRPBF FAQ
1.How can I place an order for LTC1235CSW#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1235CSW#TRPBF 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 LTC1235CSW#TRPBF reliable?
The price and inventory of LTC1235CSW#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1235CSW#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC1235CSW#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1235CSW#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1235CSW#TRPBF?
LTC1235CSW#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1235CSW#TRPBF 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 LTC1235CSW#TRPBF?
For technical support, including LTC1235CSW#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1235CSW#TRPBF requirements.
6.How does Aetrix verify that LTC1235CSW#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC1235CSW#TRPBF 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 LTC1235CSW#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC1235CSW#TRPBF?
All LTC1235CSW#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1235CSW#TRPBF, 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 LTC1235CSW#TRPBF part is unused and in its original packaging.
Return procedure for LTC1235CSW#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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