LTC1235 - Microprocessor Supervisory Circuit
Features
- Guaranteed Reset Assertion at VCC = 1V
- 1.5mA Maximum Supply Current
- Fast (35ns Max.) Onboard Gating of RAM Chip Enable Signals
- Conditional Battery Backup Extends Battery Life
- 4.65V Precision Voltage Monitor
- Power OK/Reset Time Delay: 200ms
- External Reset Control
- Minimum External Component Count
- 1µA Maximum Standby Current
- Voltage Monitor for Power Fail or Low Battery Warning
- Thermal Limiting
- Performance Specified Over Temperature
- All the LTC695 Features Plus Conditional Battery Backup and External Reset Control
Typical Application
Description
The LTC1235 provides complete power supply monitoring and battery control functions for microprocessor reset, battery backup, RAM write protection, power failure warning and watchdog timing. The LTC1235 has all the LTC695 features plus conditional battery backup and external reset control. When an out-of-tolerance power supply condition occurs, the reset outputs are forced to active states and the Chip Enable output write-protects external memory. The RESET output is guaranteed to remain logic low with VCC as low as 1V. External reset control is provided by a debounced push-button reset input.
The LTC1235 powers the active CMOS RAMs with a charge pumped NMOS power switch to achieve low dropout and low supply current. When primary power is lost, auxiliary power, connected to the battery input pin, provides backup power to the RAMs. The LTC1235 can be programmed by a µP signal to either back up the RAMs or not. This extends the battery life in situations where RAM data need not always be saved when power goes down.
For an early warning of impending power failure, the LTC1235 provides an internal comparator with a user-defined threshold. An internal watchdog timer is also available, which forces the reset pins to active states when the watchdog input is not toggled prior to the time-out period.
Packaging
CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.
For complete and up to date package information and drawings, please refer to our packaging page
| Part Number | Package | Code | Temp | Package Drawing |
RoHS |
|---|---|---|---|---|---|
| LTC1235CN#PBF | N-16 | N | C | 05-08-1510 (N16) | Yes |
| LTC1235CSW#PBF | SW-16 | SW | C | 05-08-1620 (SW16) | Yes |
| LTC1235CSW#TRPBF | SW-16 | SW | C | 05-08-1620 (SW16) | Yes |
Order Info
- Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
- Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
- Please refer to our general ordering information or the product datasheet for more details
Package Variations and Pricing
| Part Number | Package | Temp | Price (1-99) |
Price (1k)* |
RoHS | |
|---|---|---|---|---|---|---|
| LTC1235CN#PBF | N-16 | C | $4.60 | $3.70 | Yes | |
| LTC1235CSW#PBF | SW-16 | C | $5.00 | $4.05 | Yes | |
| LTC1235CSW#TRPBF | SW-16 | C | $4.11 | Yes | ||
| Buy Now • Request Samples | ||||||
Demo Boards
Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.Click here to view our complete list of demo boards
Applications
- Critical µP Power Monitoring
- Intelligent Instruments
- Battery-Powered Computers and Controllers
- Automotive Systems
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Design Tools
LTspice
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Models for the following parts are available in LTspice:
LTC1235
Technical Support
- For immediate technical assistance, contact your local sales office or distributor or call 1-800-4-LINEAR (US customers only) or 408-432-1900.
- For less urgent requests, please complete our Technical Support Request Form. Please allow 2-3 business days for reply.
