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Analog Devices Inc. LT1938IDD#TRPBF
- Part No.:
- LT1938IDD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT1938IDD#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 2.2A 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,431
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Product details
Overview
LT1938IDD#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic current-mode step-down switching regulator with 3.6V–25V input range, 2.2A output current capability, and adjustable 300kHz–2.8MHz switching frequency. It integrates a 0.18Ω NPN power switch, on-chip boost Schottky diode, and power-good flag, enabling compact, high-efficiency DC/DC conversion in automotive battery regulation and portable power systems.
For engineers reviewing the LT1938IDD#TRPBF datasheet, LT1938IDD#TRPBF pinout, LT1938IDD#TRPBF application, or LT1938IDD#TRPBF equivalent, key selection criteria include its thermally enhanced 10-pin 3mm × 3mm DFN package, 1.265V feedback reference, soft-start via RUN/SS pin, and integrated bias path for efficiency optimization when VOUT > 3V.
Technical Context
The LT1938IDD#TRPBF employs constant-frequency current-mode control with an external RT resistor setting oscillator frequency between 300kHz and 2.8MHz. Its internal error amplifier drives the VC pin to regulate peak switch current, while slope compensation ensures stability across duty cycles.
Operation relies on a bipolar NPN switch driven by the BOOST pin-charged via an external capacitor and internal Schottky diode-to achieve full saturation. The BIAS pin enables efficient operation by sourcing control circuitry power from VOUT when ≥3V, reducing VIN quiescent draw to <0.5µA in shutdown.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 25V - supports wide-range industrial and automotive supplies without external pre-regulation |
| Max Output Current | 2.2A - delivers sufficient power for FPGA core rails, DSPs, and multi-rail embedded systems |
| Switching Frequency | 300kHz to 2.8MHz - enables tradeoff between small ceramic LC components and efficiency at light loads |
| Feedback Reference | 1.265V ±10mV - sets output voltage accuracy and enables precise resistor-divider programming from 1.265V to 20V |
| Shutdown Current | <1µA - minimizes battery drain in always-on portable or telematics applications |
| Power Good Threshold | 90% of programmed VOUT - provides reliable sequencing signal for downstream logic or microcontrollers |
| On-Resistance (SW) | 0.18Ω typical - reduces conduction loss and thermal rise at full load, supporting 12V→3.3V/2.2A conversion |
Pinout & Package
The LT1938IDD#TRPBF is housed in a thermally enhanced 10-lead 3mm × 3mm plastic DFN package with exposed pad (Pin 11), requiring soldering to PCB ground for optimal thermal performance (θJC = 10°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BD (1) | Boost Diode Anode | Connects to internal Schottky anode; ties to BOOST capacitor cathode for charge pump operation |
| BOOST (2) | Charge Pump Drive | Provides >VIN voltage to fully saturate NPN switch; requires external capacitor to SW |
| SW (3) | Switch Node | Drives inductor and catch diode; carries high di/dt pulses; must be routed with minimal loop area |
| VIN (4) | Main Power Input | Supplies switch and internal regulator; requires local 4.7µF ceramic bypass near pin |
| RUN/SS (5) | Enable & Soft-Start | Logic-level enable (≥2.5V = ON); RC network here controls output voltage ramp rate |
| PG (6) | Power-Good Flag | Open-collector output active low until FB reaches 90% of target; needs pull-up to BIAS or VOUT |
| BIAS (7) | Efficiency Bias Supply | Accepts ≥3V external supply (e.g., VOUT) to reduce VIN quiescent current and improve light-load efficiency |
| FB (8) | Feedback Input | Regulated to 1.265V; connects to resistor divider tap for output voltage programming |
| VC (9) | Error Amplifier Output | Controls peak switch current; RC network to ground sets loop compensation poles/zeros |
| RT (10) | Oscillator Frequency Set | Resistor to GND programs switching frequency per datasheet table (e.g., 8.66kΩ = 2.8MHz) |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Boost Schottky Diode | Eliminates external diode, reduces BOM count and board area, and enables self-contained charge-pump drive |
| Thermally Enhanced DFN Package | 3mm × 3mm footprint with exposed GND pad achieves θJA = 45°C/W, enabling 2.2A operation without heatsink |
| Adjustable Frequency via RT Pin | Single resistor selects 300kHz–2.8MHz - allows optimization for EMI, size, or efficiency in each design |
| Power-Good Flag with Hysteresis | 100mV threshold offset + 10mV hysteresis ensures clean sequencing and avoids false toggling during line/load transients |
| Bias-Switching Architecture | Automatic selection of BIAS or VIN as control rail improves efficiency by up to 3% at light loads when VOUT ≥ 3.3V |
Applications
| Automotive Battery Regulation | Portable Product Power |
|---|---|
Use Scenario: Regulating 12V vehicle battery (9V–16V nominal, up to 25V load dump) to 3.3V/5V for infotainment MCU and CAN transceivers. IC Role / Device Role / Timing Role: Primary buck converter providing stable, ripple-controlled supply with power-good signaling for safe boot sequence. Use Value: Withstands 25V transients, maintains regulation down to 3.6V cold-crank, and delivers 2.2A for multi-core SoC subsystems. | Use Scenario: Powering handheld medical devices or ruggedized tablets where battery life and board space are critical constraints. IC Role / Device Role / Timing Role: High-efficiency step-down regulator converting single-cell Li-ion (3.0V–4.2V) or dual-cell (6V–8.4V) to 3.3V system rail. Use Value: <1µA shutdown current extends shelf life; 2.8MHz operation enables 1µH inductor and 4.7µF ceramic output cap for ultra-compact layout. |
| Distributed Supply Regulation | Industrial Supplies |
Use Scenario: Local point-of-load conversion in PLC backplanes or sensor nodes where 24V bus powers multiple isolated 5V/3.3V rails. IC Role / Device Role / Timing Role: Standalone buck regulator delivering regulated 5V at 2.2A per module, with PG flag enabling fault isolation. Use Value: Adjustable frequency avoids noise coupling with adjacent clock domains; 25V absolute max rating tolerates 24V bus surges. | Use Scenario: Replacing linear regulators in factory automation I/O modules requiring 5V/2A from unregulated 12V–24V field wiring. IC Role / Device Role / Timing Role: Efficient switching alternative to LM7805, reducing thermal load and enabling fanless enclosure design. Use Value: 0.18Ω switch RDS(on) limits temperature rise to <35°C rise at full load, eliminating need for heatsinking. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3630EMSE#PBF | Higher 4MHz max frequency, lower 1.5A output, integrated MOSFETs, no BOOST pin | Better for ultra-small footprints but limited to ≤1.5A; lacks charge-pump drive for bipolar switch saturation | Select when 1.5A suffices and board area is more critical than peak current or 25V transient tolerance |
| TPS54227PWPR | 2.95V–6V input range, 2.2A output, integrated FETs, 700kHz–2.2MHz, no BIAS pin | Not suitable for 12V+ inputs; optimized for low-VIN point-of-load, lacks bias-switching efficiency mode | Choose only for sub-6V applications where BIAS efficiency gain is irrelevant and 25V rating is unnecessary |
Compared with LTC3630EMSE#PBF and TPS54227PWPR, the LT1938IDD#TRPBF uniquely combines 25V input tolerance, 2.2A output, integrated boost diode, and BIAS-driven efficiency-making it irreplaceable in automotive and wide-input industrial designs where those features are mandatory.
Availability
LT1938IDD#TRPBF is available at Aetrix Electronics and suitable for automotive battery regulation, portable product power, and distributed supply regulation requiring stable component supply across extended temperature ranges (–40°C to 125°C).
Supply support for LT1938IDD#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) is a global leader in high-performance analog, mixed-signal, and power management ICs, serving precision instrumentation, industrial, automotive, and communications markets.
The LT1938IDD#TRPBF belongs to Linear's legacy high-voltage monolithic buck regulator family, designed specifically for robust, wide-input DC/DC conversion in harsh environments where reliability, thermal performance, and transient immunity are critical.
FAQ
What is the maximum input voltage rating for LT1938IDD#TRPBF?
The LT1938IDD#TRPBF has an absolute maximum VIN rating of 25V. It safely handles automotive load-dump transients up to this level when operating in regulation mode. During startup or short-circuit conditions, the maximum allowable VIN depends on switching frequency and duty cycle constraints-consult the "Input Voltage Range" section of the datasheet for frequency-dependent derating equations.
Does LT1938IDD#TRPBF require an external catch diode?
No, the LT1938IDD#TRPBF does not require an external catch diode. It integrates a boost Schottky diode (connected to BD pin) and uses the BOOST pin to drive the internal bipolar NPN switch, eliminating the need for an external freewheeling diode in standard buck configurations.
How is output voltage programmed on LT1938IDD#TRPBF?
The LT1938IDD#TRPBF output voltage is programmed using a resistor divider from VOUT to GND, with the midpoint connected to the FB pin. The internal 1.265V reference determines the ratio: R1 = R2 × ((VOUT / 1.265) – 1). For example, to set 5.0V output with R2 = 10kΩ, R1 = 29.4kΩ (1% tolerance recommended).
What thermal performance can be expected from LT1938IDD#TRPBF in a standard PCB layout?
With the exposed pad (Pin 11) soldered to a minimum 100mm² copper pour tied to internal/external GND planes, the LT1938IDD#TRPBF achieves θJA ≈ 45°C/W. At 2.2A output with 12V input → 3.3V, junction temperature rise is typically <45°C above ambient-well within the –40°C to 125°C operating range.
Can LT1938IDD#TRPBF operate with input voltage below 3.6V?
No, the LT1938IDD#TRPBF requires a minimum input voltage of 3.6V to maintain regulation. Below this, the internal regulator cannot sustain bias and control circuitry operation. Startup may fail, and output voltage will drop out of specification. This limit is absolute-not dependent on load or temperature.
LT1938IDD#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-WFDFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3.6V
- Voltage - Input (Max):
- 25V
- Voltage - Output (Min/Fixed):
- 1.265V
- Voltage - Output (Max):
- 20V
- Current - Output:
- 2.2A
- Frequency - Switching:
- 300kHz ~ 3MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-DFN (3x3)
LT1938IDD#TRPBF FAQ
1.How can I place an order for LT1938IDD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1938IDD#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 LT1938IDD#TRPBF reliable?
The price and inventory of LT1938IDD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1938IDD#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1938IDD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1938IDD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1938IDD#TRPBF?
LT1938IDD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1938IDD#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 LT1938IDD#TRPBF?
For technical support, including LT1938IDD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1938IDD#TRPBF requirements.
6.How does Aetrix verify that LT1938IDD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1938IDD#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 LT1938IDD#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1938IDD#TRPBF?
All LT1938IDD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1938IDD#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 LT1938IDD#TRPBF part is unused and in its original packaging.
Return procedure for LT1938IDD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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