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Analog Devices Inc. LT1937ES5#TRMPBF
- Part No.:
- LT1937ES5#TRMPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- SOT-23-5 Thin, TSOT-23-5
- Datasheet:
-
LT1937ES5#TRMPBF.pdf
- Description:
- IC LED DRVR RGLTR PWM TSOT23-5
- Quantity:
- Payment:
- Shipping:
Inventory:4,654
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Product details
Overview
LT1937ES5#TRMPBF from Analog Devices (formerly Linear Technology) is a constant-current step-up DC/DC converter IC designed specifically to drive white LED strings in portable electronics. It delivers up to 20mA per string, operates from 2.5V to 10V input, switches at 1.2MHz, and features a 95mV feedback reference for high-efficiency current regulation - used in Li-ion–powered devices requiring uniform brightness across 2–4 series LEDs.
For engineers reviewing the LT1937ES5#TRMPBF datasheet, LT1937ES5#TRMPBF pinout, LT1937ES5#TRMPBF application, or LT1937ES5#TRMPBF equivalent, key selection criteria include its 36V bipolar switch rating, SC70/TSOT-23 package compatibility, 84% typical efficiency at 15mA, minimal external component count (0.22µF output cap), and shutdown-controlled PWM dimming capability.
Technical Context
The LT1937ES5#TRMPBF uses constant-frequency current-mode control with an internal 1.2MHz oscillator and a 95mV precision feedback reference. Its PWM comparator compares a ramp-modulated switch-current signal against the error amplifier's output, enabling tight line/load regulation without pulse skipping down to ~4mA.
It integrates a rugged 36V bipolar power switch with 350mV VCE(SAT) at 250mA and supports both analog and PWM dimming via the SHDN and FB pins. The device lacks internal soft-start but allows external RC soft-start implementation to limit inrush current.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.5V to 10V - supports single-cell Li-ion (3.0–4.2V) and 5V USB-supplied systems. |
| Switching Frequency | 1.2MHz (typ) - enables use of sub-2mm-height inductors and 0.22µF ceramic output capacitors. |
| Feedback Reference | 95mV (typ) - minimizes I2R loss in current-sense resistor for >84% efficiency at 15mA. |
| Max Switch Voltage | 36V - safely drives up to six white LEDs (≈30V total VF) from 5V input. |
| Shutdown Current | 0.1µA (max) - ensures ultra-low quiescent drain during display-off states in battery-powered devices. |
| Operating Temp Range | –40°C to +85°C - qualified for extended commercial environments including handhelds and GPS receivers. |
| Switch Current Limit | 320mA - provides robust overcurrent protection while supporting ≥4-LED strings at full brightness. |
Pinout & Package
LT1937ES5#TRMPBF is housed in a 5-lead TSOT-23 (S5) package - low-profile, surface-mount, 2.9mm × 1.6mm footprint with 0.95mm height - optimized for space-constrained portable PCBs.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (Pin 1) | Switch Node | Connects to inductor and Schottky diode anode; carries high dv/dt switching waveform - requires minimized trace area to reduce EMI. |
| GND (Pin 2) | Power Ground | Main return path for switch current and feedback resistor; must connect directly to local ground plane. |
| FB (Pin 3) | Current Sense Input | Monitors voltage across external sense resistor; regulated to 95mV to set LED current as ILED = 95mV/RFB. |
| SHDN (Pin 4) | Enable/Disable Control | Logic-level input: ≥1.5V enables regulator; ≤0.4V disables it - supports PWM dimming and system-level power gating. |
| VIN (Pin 5) | Input Supply | Primary power input (2.5–10V); requires local 1µF X5R/X7R ceramic bypass capacitor placed near the pin. |
Key Features
| Feature | Design Value |
|---|---|
| Inherently matched LED current | Series LED connection ensures identical current through all diodes - eliminates brightness variation and ballast resistors. |
| High-frequency operation | 1.2MHz fixed switching frequency allows compact magnetics (e.g., 22µH Murata LQH3C-220) and tiny 0.22µF output caps. |
| Low-feedback-voltage architecture | 95mV reference reduces power dissipation in RFB, improving thermal performance and efficiency at high LED currents. |
| Rugged 36V bipolar switch | Supports up to six white LEDs from 5V input without external clamp circuitry - simplifies BOM and layout. |
| Flexible dimming interface | SHDN pin accepts 1–10kHz PWM; FB pin supports analog dimming via DC voltage or filtered PWM - no additional IC required. |
Applications
| Cellular Phones | PDAs & Handheld Computers |
|---|---|
Use Scenario: Backlighting for small-format TFT displays in GSM/3G handsets with single Li-ion cell power. IC Role / Device Role / Timing Role: Constant-current boost controller regulating 3-series white LEDs at 15mA with 84% efficiency. Use Value: Enables uniform brightness, eliminates discrete current-setting resistors, and reduces board area by >30% vs. linear solutions. | Use Scenario: Display backlight in QVGA-resolution PDAs operating from 3.3V or Li-ion battery. IC Role / Device Role / Timing Role: Step-up converter driving four white LEDs in series using 22µH inductor and 0.22µF output capacitor. Use Value: Delivers stable current despite input voltage sag (3.0–4.2V), supports PWM dimming via SHDN pin for user-adjustable brightness. |
| Digital Cameras | GPS Receivers |
Use Scenario: Flash-assist or LCD backlight in compact digital cameras powered by dual AA or Li-ion cells. IC Role / Device Role / Timing Role: High-efficiency LED driver delivering up to 20mA to two or three LEDs with <100ns shutdown response. Use Value: Minimizes battery drain during standby (0.1µA shutdown current) and maintains consistent color temperature across LED string. | Use Scenario: Status indicator and map-display backlight in automotive-grade portable GPS units. IC Role / Device Role / Timing Role: Robust LED driver operating across –40°C to +85°C ambient, supporting open-circuit protection via external Zener. Use Value: Ensures reliable illumination under wide temperature swings and transient input conditions without firmware intervention. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar white LED boost converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1932ES5#TRMPBF | Same S5 package; higher LED count support (up to 8 from 3V), 1.2MHz switching, but 1.2V min input vs. LT1937ES5#TRMPBF's 2.5V. | Better suited for ultra-low-voltage systems (e.g., coin-cell–powered devices); less margin at Li-ion discharge end. | Select LT1932ES5#TRMPBF only if driving ≥5 LEDs from ≤3.3V is required; otherwise LT1937ES5#TRMPBF offers tighter current matching at lower cost. |
| LTC3200ES6#TRMPBF | Inductorless charge-pump topology; 2MHz, 100mA output; MS8/ThinSOT-6 package; no magnetic components needed. | Lower EMI and smaller solution size, but limited to ≤6 LEDs and lower efficiency (~75%) at 15mA vs. LT1937ES5#TRMPBF's 84%. | Choose LTC3200ES6#TRMPBF when board space is critical and inductor placement is problematic; prefer LT1937ES5#TRMPBF for higher efficiency and better thermal performance in sustained-brightness use cases. |
Compared with LT1937ES5#TRMPBF, LT1932ES5#TRMPBF extends LED count capability at lower input voltages but sacrifices some current accuracy at light loads, while LTC3200ES6#TRMPBF eliminates magnetics at the expense of peak efficiency and output voltage headroom - making LT1937ES5#TRMPBF the optimal balance of efficiency, simplicity, and thermal robustness for 2–4 LED strings.
Availability
LT1937ES5#TRMPBF is available at Aetrix Electronics and suitable for cellular phones, PDAs, digital cameras, and GPS receivers requiring stable component supply, long-lifecycle support, and guaranteed traceable sourcing.
Supply support for LT1937ES5#TRMPBF 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 full product support, documentation, and manufacturing continuity for legacy Linear parts including the LT1937 family.
The LT1937 product line was engineered for space-constrained, battery-powered portable electronics requiring high-efficiency, constant-current white LED backlighting with minimal external components.
FAQ
What is the minimum input voltage required for LT1937ES5#TRMPBF to regulate three white LEDs?
The LT1937ES5#TRMPBF requires a minimum input voltage of 2.5V to operate. For three white LEDs (typical VF ≈ 3.0–3.6V each), regulation begins reliably at ≥3.2V input - confirmed by Figure 1 and Typical Application circuits in the datasheet. Below this, dropout occurs and current regulation degrades.
Can LT1937ES5#TRMPBF drive six white LEDs, and what input voltage is needed?
Yes, LT1937ES5#TRMPBF can drive up to six white LEDs when supplied from 5V, as stated in the FEATURES section and verified in the "5V to Seven White LEDs" application (Figure TA04a). At 5V input, six LEDs (≈28–32V total VF) are supported within the 36V switch rating - though efficiency drops to ~75% at 15mA.
What is the recommended output capacitor value for LT1937ES5#TRMPBF, and why?
The recommended output capacitor for LT1937ES5#TRMPBF is 0.22µF ceramic (X5R or X7R dielectric), as specified in the Typical Applications and Capacitor Selection sections. This value stabilizes the feedback loop at 1.2MHz, minimizes board area, and maintains <100mVpp ripple at 15mA load - validated across temperature in Figure TA01b.
How does the FB pin of LT1937ES5#TRMPBF set LED current, and what resistor tolerance is advised?
The FB pin regulates voltage to 95mV (typ), so LED current is calculated as ILED = 95mV / RFB. A 1% tolerance resistor is recommended (e.g., 6.34Ω for 15mA) to ensure ±1% current accuracy - critical for display uniformity. The FB pin bias current (10–100nA) introduces negligible error at standard RFB values.
Does LT1937ES5#TRMPBF include built-in soft-start, and how is inrush current managed?
No, LT1937ES5#TRMPBF has no internal soft-start. At turn-on, inrush current peaks near 200mA (Figure F10). To limit this, an external RC soft-start circuit is recommended (Figure F11a): a 100kΩ resistor and 1nF capacitor between VIN and SHDN, delaying enable until input stabilizes - reducing stress on input capacitors and power sources.
LT1937ES5#TRMPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- SOT-23-5 Thin, TSOT-23-5
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- DC DC Regulator
- Topology:
- Step-Up (Boost)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 2.5V
- Voltage - Supply (Max):
- 10V
- Voltage - Output:
- 36V
- Current - Output / Channel:
- 320mA (Switch)
- Frequency:
- 1.2MHz
- Dimming:
- Analog, PWM
- Applications:
- Backlight
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- TSOT-23-5
LT1937ES5#TRMPBF FAQ
1.How can I place an order for LT1937ES5#TRMPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1937ES5#TRMPBF 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 LT1937ES5#TRMPBF reliable?
The price and inventory of LT1937ES5#TRMPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1937ES5#TRMPBF is usually 5 days.
3.What payment methods are accepted for LT1937ES5#TRMPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1937ES5#TRMPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1937ES5#TRMPBF?
LT1937ES5#TRMPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1937ES5#TRMPBF 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 LT1937ES5#TRMPBF?
For technical support, including LT1937ES5#TRMPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1937ES5#TRMPBF requirements.
6.How does Aetrix verify that LT1937ES5#TRMPBF is sourced from the original manufacturer or authorized distributors?
All LT1937ES5#TRMPBF 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 LT1937ES5#TRMPBF meets industry standards.
7.What is the process for return or replacement of LT1937ES5#TRMPBF?
All LT1937ES5#TRMPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1937ES5#TRMPBF, 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 LT1937ES5#TRMPBF part is unused and in its original packaging.
Return procedure for LT1937ES5#TRMPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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