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Analog Devices Inc. LT1241CS8#TRPBF
- Part No.:
- LT1241CS8#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1241CS8#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,161
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Product details
Overview
LT1241CS8#TRPBF from Analog Devices is an 8-pin, fixed-frequency current-mode PWM controller IC optimized for off-line and DC/DC converters. It delivers <250µA start-up current, 50ns current sense delay, 500kHz max switching frequency (via 1MHz oscillator), and a ±1A totem-pole output stage for direct MOSFET gate drive in AC-DC power supplies.
For engineers reviewing the LT1241CS8#TRPBF datasheet, LT1241CS8#TRPBF pinout, LT1241CS8#TRPBF application, or LT1241CS8#TRPBF equivalent, key selection criteria include undervoltage lockout thresholds (9.6V start-up), 5V trimmed reference accuracy (±1%), leading-edge blanking (100ns), and compatibility with UC1842-series designs requiring improved speed and lower quiescent current.
Technical Context
The LT1241CS8#TRPBF implements a fixed-frequency current-mode control architecture with a trimmed 8.2mA oscillator sink current and tightly specified oscillator frequency (±5% over temperature). Its error amplifier features 90dB DC gain and 1MHz unity-gain bandwidth, with internal 2.5V feedback reference derived from the 5V bandgap VREF.
Current sensing uses a comparator with 1V clamp and programmable threshold via error amplifier output offset (1.4V–4.4V range), enabling precise peak-current limiting. Undervoltage lockout actively pulls down both OUTPUT (Pin 6) and VREF (Pin 8) to ~1V during fault conditions, eliminating external pull-down resistors.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Operating Frequency | Up to 500kHz output switching (1MHz oscillator); enables high-density SMPS designs with reduced magnetics size. |
| Start-Up Current | <250µA (170µA typ); minimizes bleed resistor losses in offline AC-DC converters. |
| Output Drive | ±1A totem-pole stage; directly drives power MOSFET gates without external buffer stages. |
| Reference Voltage | 5.000V ±1% (4.925–5.075V); powers RT/CT timing network and provides stable bias for internal circuitry. |
| Current Sense Delay | 50ns (typ); ensures fast overcurrent response while maintaining stability under transient load steps. |
| UVLO Threshold | 9.6V start-up / 7.6V minimum operating voltage with 2.0V hysteresis; prevents erratic operation during brownout conditions. |
| Output Clamp | 18V max high-level output; protects MOSFET gate oxide from overvoltage stress during transients. |
Pinout & Package
S8 package: 8-lead plastic SOIC, RoHS-compliant, 0°C to 100°C operating temperature range.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| COMP (1) | Error amplifier output | Provides loop compensation node; sources 0.5mA / sinks 2mA; used to set current sense clamp level. |
| FB (2) | Inverting input of error amplifier | Receives voltage feedback via resistive divider; internally referenced to 2.5V; blanking time varies with FB voltage. |
| ISENSE (3) | Current sense comparator input | Detects MOSFET source current via sense resistor; includes 100ns leading-edge blanking to suppress noise spikes. |
| RT/CT (4) | Oscillator timing node | Connects external RT (to VREF) and CT (to GND); sets frequency and deadtime via trimmed 8.2mA discharge current. |
| GND (5) | Analog ground reference | Common return for feedback, oscillator, and current sense circuits; must be star-connected to minimize noise coupling. |
| OUTPUT (6) | High-current PWM output | Drives MOSFET gate directly; ±1A capability; clamped to 18V; actively pulled low (~1V) during UVLO. |
| VCC (7) | Power supply input | Accepts 7.6V–25V; powers internal logic; bypassed with ≥0.1µF capacitor near pin. |
| VREF (8) | 5V precision reference output | Supplies timing current to RT; powers internal bias networks; can source up to 20mA for external circuitry. |
Key Features
| Feature | Design Value |
|---|---|
| Current mode control | Enables cycle-by-cycle peak current limiting and inherent line feedforward for improved transient response. |
| Leading-edge blanking | 100ns fixed blanking window synchronized to switch turn-on, eliminating need for RC filter at ISENSE pin. |
| Trimmed oscillator | Initial frequency accuracy ±5% with tight sink current (8.2mA ±0.3mA), ensuring consistent deadtime across units. |
| Active UVLO pull-down | Internal Darlington PNP pulls OUTPUT and VREF to ~1V during undervoltage, removing need for external gate pull-down resistors. |
| 1A totem-pole output | Eliminates external driver stages; supports fast rise/fall times (40ns/30ns into 1nF) for high-efficiency switching. |
Applications
| AC-DC Off-Line Power Supplies | Isolated DC-DC Converters |
|---|---|
Use Scenario: 90–240VAC input converted to regulated 12V/1.5A output using flyback topology with primary-side regulation. IC Role / Device Role / Timing Role: Primary-side PWM controller providing current-mode feedback, oscillator timing, and MOSFET gate drive. Use Value: Low start-up current (<250µA) reduces standby losses; 500kHz switching enables compact transformer and EMI filter design. | Use Scenario: 48V telecom input stepped down to isolated 5V/10A output using forward converter with synchronous rectification. IC Role / Device Role / Timing Role: Secondary-side current-mode controller managing duty cycle based on isolated current sense signal. Use Value: 1V current sense clamp ensures predictable short-circuit current limiting; ±1A output drives synchronous MOSFETs directly. |
| Industrial Motor Drives | LED Constant-Current Drivers |
Use Scenario: 24V DC bus powering 3-phase BLDC motor with integrated gate drivers and current sensing. IC Role / Device Role / Timing Role: PWM generator for three half-bridge drivers, synchronized via external clock input on RT/CT pin. Use Value: External clock synchronization capability (TA03 schematic) enables precise phase alignment across multiple controllers. | Use Scenario: High-brightness LED string (36V, 700mA) driven from 12V automotive supply using boost topology. IC Role / Device Role / Timing Role: Constant-current PWM controller regulating LED current via ISENSE feedback and slope compensation. Use Value: Adjustable current sense clamp (via COMP pin) allows precise LED current setting without changing sense resistor value. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar PWM controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UC3842N | Higher start-up current (1mA), no leading-edge blanking, no active UVLO pull-down, 250kHz max frequency. | Requires external blanking filter and gate pull-down resistor; less suitable for high-density or low-standby designs. | Lower-cost option where 500kHz operation and ultra-low start-up current are not required. |
| TL494CN | Fixed-frequency voltage-mode controller; dual-output push-pull; no integrated current sense comparator or blanking. | Requires external current sensing and protection circuitry; better suited for dual-rail or center-tapped topologies. | Preferred when dual-output capability or adjustable deadtime is needed, but adds system complexity for basic flyback. |
Compared with UC3842N and TL494CN, the LT1241CS8#TRPBF offers superior integration for single-switch current-mode converters-reducing BOM count via built-in blanking, active UVLO, and 1A gate drive-while enabling higher switching frequencies and lower standby power.
Availability
LT1241CS8#TRPBF is available at Aetrix Electronics and suitable for AC-DC power supplies, isolated DC-DC converters, and industrial motor drives requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LT1241CS8#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 (now part of Analog Devices, Inc. following merger with Linear Technology) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors.
The LT1241 series belongs to Linear Technology's legacy PWM controller product line, specifically engineered for high-efficiency, high-reliability switch-mode power conversion in demanding industrial and telecom applications.
FAQ
What is the maximum recommended switching frequency for LT1241CS8#TRPBF in practical designs?
The LT1241CS8#TRPBF supports up to 500kHz output switching frequency (1MHz oscillator), validated in typical applications like the 300kHz off-line power supply (TA06). At 500kHz, layout parasitics and gate drive strength become critical; use short, low-inductance traces and ensure adequate PCB copper for the OUTPUT pin. The device's 40ns rise/30ns fall time into 1nF confirms its suitability for this frequency range without external buffering.
How does the LT1241CS8#TRPBF implement leading-edge blanking, and what is its duration?
The LT1241CS8#TRPBF integrates a fixed-duration leading-edge blanking circuit at the ISENSE comparator output, activated synchronously with each OUTPUT turn-on edge. Blanking time is 100ns under normal operation (VFB = 2.5V) and scales linearly toward zero as FB voltage decreases-ensuring minimal delay during startup or short-circuit faults. This eliminates external RC filters while preserving fast fault response.
Can the LT1241CS8#TRPBF drive a MOSFET directly without an external gate driver?
Yes, the LT1241CS8#TRPBF features a ±1A totem-pole output stage explicitly designed for direct MOSFET gate drive. Its 40ns rise and 30ns fall times into 1nF capacitive load meet requirements for most power MOSFETs up to ~500kHz. For very high-Qg devices (>50nC), verify gate charge delivery using the 1A peak current and ensure thermal limits are observed under continuous switching.
What is the purpose of the active pull-down on VREF and OUTPUT during undervoltage lockout?
During UVLO, the LT1241CS8#TRPBF uses internal Darlington PNP transistors to actively pull VREF (Pin 8) and OUTPUT (Pin 6) to ~1V. This eliminates external pull-down resistors previously required to hold the MOSFET gate low and reset soft-start capacitors. The VREF pull-down can directly discharge external soft-start networks, simplifying design and improving reliability in brownout recovery.
How is the current sense threshold adjusted on the LT1241CS8#TRPBF?
The LT1241CS8#TRPBF sets current sense threshold by scaling the COMP pin voltage: a 1.4V–4.4V range at COMP yields 0–1V at ISENSE, with 1V clamping the maximum threshold. To adjust, connect a Zener or resistor divider from COMP to GND or VREF-e.g., clamping COMP at 3.4V sets a 0.667V ISENSE threshold. This allows precise peak-current limiting without changing the sense resistor value.
LT1241CS8#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive, Isolation Capable
- Topology:
- Buck
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 8.2V ~ 25V
- Frequency - Switching:
- 500kHz
- Duty Cycle (Max):
- 48%
- Synchronous Rectifier:
- No
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Frequency Control
- Operating Temperature:
- 0°C ~ 100°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1241CS8#TRPBF FAQ
1.How can I place an order for LT1241CS8#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1241CS8#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 LT1241CS8#TRPBF reliable?
The price and inventory of LT1241CS8#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1241CS8#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1241CS8#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1241CS8#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1241CS8#TRPBF?
LT1241CS8#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1241CS8#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 LT1241CS8#TRPBF?
For technical support, including LT1241CS8#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1241CS8#TRPBF requirements.
6.How does Aetrix verify that LT1241CS8#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1241CS8#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 LT1241CS8#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1241CS8#TRPBF?
All LT1241CS8#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1241CS8#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 LT1241CS8#TRPBF part is unused and in its original packaging.
Return procedure for LT1241CS8#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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