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Analog Devices Inc. LT1938EDD#TRPBF
- Part No.:
- LT1938EDD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT1938EDD#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 2.2A 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:7,229
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Product details
Overview
LT1938EDD#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic current-mode step-down switching regulator with adjustable frequency (300 kHz to 2.8 MHz), 25 V max input, 2.2 A output current capability, and integrated 0.18 Ω NPN switch and boost Schottky diode. It delivers regulated 3.3 V or 5 V outputs in space-constrained industrial power supplies and portable product battery regulation.
For engineers reviewing the LT1938EDD#TRPBF datasheet, LT1938EDD#TRPBF pinout, LT1938EDD#TRPBF application, or LT1938EDD#TRPBF equivalent, key selection criteria include its 1.265 V feedback reference, soft-start via RUN/SS pin, power good flag, thermal performance in the 3 mm × 3 mm DFN package, and compatibility with ceramic output capacitors for low ripple.
Technical Context
The LT1938EDD#TRPBF employs constant-frequency current-mode control with an internal transconductance error amplifier (330 µmho) and slope compensation, enabling fast transient response and stable loop behavior across wide input/output ratios. Its oscillator frequency is set externally via RT pin resistor (e.g., 8.66 kΩ for 2.8 MHz), and it features frequency foldback during startup or overload to limit peak inductor current.
Operation relies on bipolar NPN switch drive using BOOST pin voltage-generated by external capacitor and internal Schottky diode-to ensure full saturation. The BIAS pin enables efficiency optimization by sourcing bias current from VOUT when VIN ≫ VOUT, reducing quiescent loss. Power good (PG) asserts at 90% of programmed VOUT with 10 mV hysteresis and valid operation above VIN = 3.6 V and RUN/SS high.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6 V to 25 V - supports automotive battery (12 V nominal) and wide-input wall adapter applications without external pre-regulation. |
| Max Output Current | 2.2 A - sufficient for powering FPGA I/O banks, microcontroller cores, or multiple peripheral rails in embedded systems. |
| Switching Frequency | 300 kHz to 2.8 MHz - selectable via RT pin resistor; higher frequencies allow smaller inductors (e.g., 4.7 µH at 800 kHz) and ceramic capacitors. |
| Feedback Reference | 1.265 V ±15 mV - sets output voltage via external resistor divider; enables precise 3.3 V, 5 V, or adjustable outputs from 1.265 V to 20 V. |
| Shutdown Current | <1 µA - achieved by pulling RUN/SS pin low; critical for battery-powered devices requiring ultra-low standby power. |
| Power Good Flag | Open-collector PG output - signals VOUT ≥ 90% of target; used for system sequencing or fault monitoring in multi-rail supplies. |
| Thermal Package | 10-lead 3 mm × 3 mm DFN with exposed pad - θJA = 45°C/W enables 2.2 A operation at TA ≤ 85°C without forced air. |
Pinout & Package
The LT1938EDD#TRPBF is housed in a thermally enhanced 10-lead (3 mm × 3 mm) plastic DFN package with exposed pad (Pin 11), which must be soldered to PCB ground for optimal thermal performance (θJC = 10°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BD (Pin 1) | Boost Diode Anode | Connects to anode of internal Schottky; ties to BOOST capacitor cathode to form charge pump for switch drive. |
| BOOST (Pin 2) | Boost Voltage Supply | Provides >VIN voltage to fully saturate internal NPN switch; requires external capacitor (e.g., 10 nF) to SW. |
| SW (Pin 3) | Switch Node | Drives external inductor and catch diode; carries high di/dt pulses; must be routed with minimal loop area. |
| VIN (Pin 4) | Main Input Supply | Powers internal regulator and switch; requires local 4.7 µF ceramic bypass close to pin. |
| RUN/SS (Pin 5) | Enable & Soft-Start Control | Logic-level enable (≥2.5 V = ON); RC network here controls output voltage ramp rate during startup. |
| PG (Pin 6) | Power Good Output | Open-collector flag pulled high externally; asserts when FB reaches 90% of 1.265 V reference. |
| BIAS (Pin 7) | Bias Supply Input | Accepts external ≥3 V source (typically VOUT); reduces quiescent loss vs. VIN-only biasing. |
| FB (Pin 8) | Feedback Input | Regulated to 1.265 V; connects to resistor divider tap; bias current ≤100 nA minimizes divider error. |
| VC (Pin 9) | Error Amplifier Output | Controls peak switch current; RC compensation network here stabilizes current-mode loop. |
| RT (Pin 10) | Frequency Set Resistor | Resistor to GND sets oscillator frequency (e.g., 60.4 kΩ → 800 kHz); tolerance directly affects fSW accuracy. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Boost Schottky Diode | Eliminates external diode and associated board space; enables efficient bipolar switch drive without discrete charge pump IC. |
| Saturating NPN Switch (0.18 Ω) | Reduces conduction loss at 2.2 A (≈0.87 W dissipation), enabling high efficiency (>90%) at 12 VIN/3.3 VOUT. |
| Adjustable Soft-Start | Controlled VOUT ramp via RUN/SS RC network prevents inrush current and input rail sag during power-up. |
| Current-Mode Control with Slope Compensation | Ensures stability across all duty cycles, including >50%, without requiring ESR in output capacitor. |
| Low Dropout Operation Support | Minimum off-time of 150 ns allows operation down to ~3.6 V input, supporting Li-ion battery discharge profiles. |
Applications
| Automotive Battery Regulation | Portable Product Power |
|---|---|
Use Scenario: Regulating 12 V vehicle battery to 3.3 V for infotainment MCU and CAN transceiver logic rails. IC Role / Device Role / Timing Role: Primary buck converter delivering clean, sequenced 3.3 V supply with PG signaling readiness to host processor. Use Value: Withstands load dump transients up to 25 V and operates down to 3.6 V during cranking; PG enables safe boot sequence initiation. | Use Scenario: Powering ARM Cortex-M7-based handheld medical device with dual 3.3 V and 5 V rails from single-cell Li-Po (3.0–4.2 V). IC Role / Device Role / Timing Role: Main step-down regulator for core logic; BIAS pin connected to 3.3 V output improves efficiency at light loads. Use Value: 1 µA shutdown current extends battery life in sleep mode; 2.8 MHz operation enables use of 2.2 µH inductor for compact layout. |
| Distributed Supply Regulation | Industrial Sensor Node Power |
Use Scenario: Local 5 V regulation from 24 V factory bus for PLC I/O module with isolated RS-485 and analog front-end. IC Role / Device Role / Timing Role: Point-of-load (POL) converter providing low-noise 5 V for precision ADC and op-amps. Use Value: Ceramic-capacitor-compatible current-mode control ensures stable regulation despite varying cable impedance; PG confirms rail integrity before sensor sampling. | Use Scenario: Powering ultra-low-power wireless sensor node (sub-GHz RF + temperature/humidity sensors) from 3.6 V primary lithium cell. IC Role / Device Role / Timing Role: Efficient buck regulator stepping 3.6 V to 1.8 V for digital logic, with RUN/SS controlled by microcontroller wake signal. Use Value: Adjustable 1.265 V reference enables precise 1.8 V output; <1 µA shutdown current matches sensor node's µA-level sleep budget. |
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 36 V input rating; 1.5 A output; integrated MOSFETs; no BOOST pin required. | Better suited for 24 V industrial inputs; lower max current limits use in 2.2 A designs. | Select if input exceeds 25 V or if synchronous rectification is preferred over external Schottky. |
| TPS54227DDAR | 2.95–6 V input range; 2 A output; integrated high-side MOSFET; fixed 600 kHz fSW. | Only suitable for low-input applications (e.g., USB-powered); lacks wide-VIN flexibility. | Choose only for cost-sensitive, narrow-input designs where 25 V tolerance is unnecessary. |
Compared with LTC3630EMSE#PBF and TPS54227DDAR, the LT1938EDD#TRPBF uniquely balances 25 V input capability, 2.2 A output, and integrated boost diode in a 3 mm × 3 mm DFN-making it optimal for automotive and wide-input industrial POL where external diode count and solution size are critical.
Availability
LT1938EDD#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 LT1938EDD#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, Inc. (including legacy Linear Technology products) designs high-performance analog, mixed-signal, and power management ICs for precision, reliability, and rugged operation in demanding environments.
The LT1938EDD#TRPBF belongs to Linear's monolithic buck regulator product line, engineered for wide-input, high-efficiency DC/DC conversion in automotive, industrial, and portable applications where thermal density and solution size are constrained.
FAQ
What is the maximum input voltage supported by the LT1938EDD#TRPBF?
The LT1938EDD#TRPBF supports up to 25 V continuous input voltage. Absolute maximum ratings specify VIN ≤ 25 V and BOOST pin voltage ≤ 50 V. During startup or overload, safe operation requires VIN < (VOUT + VD + VSW) / (1 – fSW × tON(MIN)), where tON(MIN) ≈ 150 ns. In steady-state regulation, brief 25 V transients are acceptable regardless of switching frequency.
How does the BIAS pin improve efficiency in the LT1938EDD#TRPBF?
The BIAS pin on the LT1938EDD#TRPBF accepts an external ≥3 V supply-typically the regulated output-to power the internal control circuitry instead of drawing from VIN. This reduces quiescent current from VIN by up to 1.5 mA when VIN ≫ VOUT (e.g., 24 V input → 3.3 V output), directly improving light-load efficiency and thermal performance.
Can the LT1938EDD#TRPBF operate in discontinuous conduction mode (DCM)?
Yes, the LT1938EDD#TRPBF can operate in DCM, especially at light loads or with high inductance values. Its current-mode architecture remains stable in DCM, and the datasheet provides graphs of maximum load current vs. input voltage for both CCM and DCM. DCM reduces switching losses but lowers maximum deliverable current due to increased peak inductor current.
What is the purpose of the BOOST pin and how is it implemented in the LT1938EDD#TRPBF?
The BOOST pin on the LT1938EDD#TRPBF supplies a voltage higher than VIN to fully saturate the internal bipolar NPN switch. It is implemented using the internal BD pin (anode of integrated Schottky) and an external capacitor connected between BOOST and SW. During switch off-time, the capacitor charges through the Schottky; during on-time, it drives the base of the NPN switch, ensuring low VCE(sat) and high efficiency.
Does the LT1938EDD#TRPBF require an external catch diode?
No, the LT1938EDD#TRPBF does not require an external catch diode because it integrates a Schottky diode connected to the BD pin. However, an external Schottky diode is still needed between SW and ground (or output) to provide the freewheeling path during switch off-time. The integrated diode only serves the BOOST charge pump function-not the main power path.
LT1938EDD#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:
- 0°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-DFN (3x3)
LT1938EDD#TRPBF FAQ
1.How can I place an order for LT1938EDD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1938EDD#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 LT1938EDD#TRPBF reliable?
The price and inventory of LT1938EDD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1938EDD#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1938EDD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1938EDD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1938EDD#TRPBF?
LT1938EDD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1938EDD#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 LT1938EDD#TRPBF?
For technical support, including LT1938EDD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1938EDD#TRPBF requirements.
6.How does Aetrix verify that LT1938EDD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1938EDD#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 LT1938EDD#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1938EDD#TRPBF?
All LT1938EDD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1938EDD#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 LT1938EDD#TRPBF part is unused and in its original packaging.
Return procedure for LT1938EDD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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