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Analog Devices Inc. LT1937ES5#TRPBF
- Part No.:
- LT1937ES5#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- SOT-23-5 Thin, TSOT-23-5
- Datasheet:
-
LT1937ES5#TRPBF.pdf
- Description:
- IC LED DRVR RGLTR PWM TSOT23-5
- Quantity:
- Payment:
- Shipping:
Inventory:4,851
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Product details
Overview
LT1937ES5#TRPBF from Analog Devices (formerly Linear Technology) is a constant-current step-up DC/DC converter IC designed specifically to drive white LEDs in series. It delivers up to 20mA LED current with 95mV feedback reference, operates from 2.5V to 10V input, switches at 1.2MHz, and supports up to four LEDs from a Li-Ion cell in portable backlighting applications.
For engineers reviewing the LT1937ES5#TRPBF datasheet, LT1937ES5#TRPBF pinout, LT1937ES5#TRPBF application, or LT1937ES5#TRPBF equivalent, key selection criteria include its 36V bipolar switch rating, SC70/TSOT-23 package compatibility, low-quiescent-current shutdown mode, and fixed-frequency current-mode control for stable LED brightness regulation.
Technical Context
The LT1937ES5#TRPBF 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 output to regulate peak inductor current and maintain constant LED current.
It integrates a 36V rugged bipolar switch capable of 320mA current limit and 350mV VCE(SAT), enabling direct driving of LED strings up to 36V total forward voltage. The device lacks internal soft-start but supports external dimming via SHDN pin PWM, FB pin analog control, or logic-level current-stepping circuits.
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 rail operation without external LDO. |
| Feedback Reference Voltage | 95mV ±9mV - enables high-efficiency current setting with minimal I²R loss in external sense resistor. |
| Switching Frequency | 1.2MHz typical - allows use of sub-3mm-height inductors and 0.22µF ceramic output capacitor. |
| Switch Current Limit | 320mA - ensures safe operation with 22µH inductors while delivering ≥15mA to 4-series LEDs. |
| Shutdown Quiescent Current | 0.1µA typical - minimizes battery drain in always-on portable devices during display-off states. |
| Operating Temperature Range | –40°C to +85°C - qualified for industrial and consumer handheld environments including GPS receivers and digital cameras. |
Pinout & Package
LT1937ES5#TRPBF is housed in a 5-lead TSOT-23 (S5) package, 2.9mm × 1.6mm × 1.0mm, with exposed pad for thermal relief. Pin 1 is SW (switch node), Pin 2 is GND, Pin 3 is FB (feedback), Pin 4 is SHDN (shutdown), and Pin 5 is VIN (input supply).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (Pin 1) | Switch Node | Connects to inductor and Schottky diode anode; requires minimized trace area to reduce EMI radiation. |
| GND (Pin 2) | Power Ground | Primary ground return path; must connect directly to local ground plane with low-inductance routing. |
| FB (Pin 3) | Current Sense Input | References 95mV; connects to cathode of lowest LED and current-setting resistor RFB = 95mV/ILED. |
| SHDN (Pin 4) | Enable/Disable Control | Active-high logic input; ≥1.5V enables regulator, ≤0.4V disables with <1µA standby current. |
| VIN (Pin 5) | Input Supply | Accepts 2.5–10V; requires local 1µF X5R/X7R ceramic bypass capacitor placed adjacent to pin. |
Key Features
| Feature | Design Value |
|---|---|
| Inherently matched LED current | Series LED configuration eliminates current mismatch and ballast resistors, ensuring uniform brightness across multi-LED arrays. |
| High conversion efficiency | 84% typical at 15mA/3.6V input driving three white LEDs - reduces thermal load and extends battery life in compact devices. |
| Rugged 36V bipolar switch | Withstands open-circuit LED string conditions and transient overvoltage without external clamping in most designs. |
| Ultra-small external components | Supports 22µH inductors under 1mm height and 0.22µF output capacitance - enables <15mm² total solution footprint. |
| Flexible dimming interfaces | Native support for PWM (via SHDN), analog DC (via FB), filtered PWM, and discrete-step logic control - no additional ICs required. |
Applications
| Cellular Phone Backlighting | Digital Camera Flash/Backlight |
|---|---|
|
Use Scenario: Driving 3–4 white LEDs for main display backlight in GSM/UMTS smartphones with Li-Ion power source. IC Role / Device Role / Timing Role: Constant-current boost controller regulating LED string current independent of forward voltage variation and battery discharge. Use Value: Maintains consistent luminance over 3.0–4.2V battery range while achieving >82% efficiency at 15mA, reducing heat and extending talk time. |
Use Scenario: Powering auxiliary white LED array for LCD viewfinder backlight and low-power flash assist in compact digital cameras. IC Role / Device Role / Timing Role: High-frequency (1.2MHz) current-regulated boost stage enabling ultra-compact PCB layout with minimal EMI filtering. Use Value: Enables use of 0.22µF X5R ceramic output cap and 22µH shielded inductor - cuts BOM cost and board area by >30% vs. 300kHz alternatives. |
| PDA Display Illumination | GPS Receiver Status Indicators |
|
Use Scenario: Providing uniform brightness across dual-row white LED backlight for QVGA touchscreen in enterprise PDAs. IC Role / Device Role / Timing Role: Precision 95mV feedback-based current source delivering matched current to series-connected LEDs without sensing resistor drift compensation. Use Value: Eliminates need for individual LED current trimming or calibration, simplifying production test and improving long-term luminance stability. |
Use Scenario: Driving single or dual white LEDs for system status, satellite lock, and navigation alerts in automotive-grade portable GPS units. IC Role / Device Role / Timing Role: Industrial-temperature-rated (–40°C to +85°C) boost converter with robust 36V switch handling cold-cranking transients on 5V-derived rails. Use Value: Ensures reliable LED illumination during vehicle ignition events where input may dip to 3.2V and rebound rapidly - no dropout or flicker. |
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#TRPBF | Same S5 package, 1.2MHz switching, but supports up to eight LEDs from 1V–10V input and includes internal soft-start. | Better suited for higher-VF LED strings (e.g., 5–8 LEDs) and systems requiring inrush current limiting. | Select LT1932ES5#TRPBF when driving >4 LEDs or needing reduced input surge current; not drop-in due to different soft-start behavior. |
| LTC3200ES6#TRMPBF | Inductorless charge pump architecture, 2MHz, fixed 5x/4x/3x/2x gain, 100mA output, MS8/ThinSOT-6 package. | Lower EMI and smaller footprint than inductive solutions, but limited to ≤6 LEDs and lower efficiency at high currents. | Choose LTC3200ES6#TRMPBF for ultra-low-noise, space-constrained designs with ≤6 LEDs and moderate current (<20mA); incompatible pinout and topology. |
Compared with LT1937ES5#TRPBF, LT1932ES5#TRPBF offers extended LED count capability and built-in soft-start at the cost of slightly higher quiescent current, while LTC3200ES6#TRMPBF trades inductor dependency for charge-pump simplicity and noise reduction - neither is pin-compatible, and both require layout and control circuit redesign.
Availability
LT1937ES5#TRPBF is available at Aetrix Electronics and suitable for cellular phone backlighting, digital camera illumination, and GPS receiver indicator applications requiring stable component supply, full lifecycle traceability, and industrial-temperature grade performance.
Supply support for LT1937ES5#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 and maintains its legacy precision analog and power management product lines with full datasheet, reliability, and support continuity.
The LT1937 belongs to Linear's white LED driver family, engineered for portable backlighting where small size, high efficiency, and inherent current matching across series LEDs are critical design requirements.
FAQ
What is the maximum number of white LEDs the LT1937ES5#TRPBF can drive from a 3.6V input?
The LT1937ES5#TRPBF can drive up to four white LEDs in series from a 3.6V input, assuming typical white LED forward voltage of ~3.2V per diode (total ~12.8V). Its 36V switch rating and 1.2MHz boost architecture enable this with standard 22µH inductors and 0.22µF output capacitance, as verified in Figure 1937 TA02a/b of the official datasheet. Efficiency remains ≥80% at 15mA load.
Does the LT1937ES5#TRPBF include internal soft-start functionality?
No, the LT1937ES5#TRPBF does not include internal soft-start. As stated in the Applications Information section, "no internal soft-start circuit is included" to minimize start-up delay. Inrush current reaches ~200mA at turn-on (Figure 1937 F10), so external soft-start - such as the RC network shown in Figure 1937 F11a - is required if controlled ramp-up is needed. This distinguishes it from later variants like LT1932ES5#TRPBF.
What is the recommended external diode for use with the LT1937ES5#TRPBF?
The recommended external diode for LT1937ES5#TRPBF is the Central Semiconductor CMDSH-3 Schottky diode (100mA rating, 0.58V @100mA, 7pF capacitance), explicitly cited in the Typical Application schematics (e.g., Figure 1937 F01a) and Table 3 of the datasheet. Its low forward voltage and minimal junction capacitance optimize efficiency at 1.2MHz switching while maintaining thermal safety under 20mA LED loads.
Can the LT1937ES5#TRPBF operate below 2.5V input?
No, the LT1937ES5#TRPBF has a minimum operating voltage of 2.5V as specified in the Absolute Maximum Ratings and Electrical Characteristics tables. Operation below this threshold is not guaranteed - startup fails and regulation is lost. For sub-2.5V applications (e.g., single alkaline or NiMH cells), alternative parts like LT1615 or LT1932 should be considered, as confirmed in the Related Parts table (Page 12).
How is LED current set on the LT1937ES5#TRPBF, and what tolerance resistor is recommended?
LED current on the LT1937ES5#TRPBF is set by a single external resistor (RFB) connected between FB pin and LED string cathode, using the formula RFB = 95mV / ILED. A 1% tolerance metal-film or thin-film resistor is recommended to ensure accurate current regulation, as stated in the "LED Current Control" section - for example, 6.34Ω yields 15mA. Precision avoids drift from temperature or manufacturing variance.
LT1937ES5#TRPBF 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#TRPBF FAQ
1.How can I place an order for LT1937ES5#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1937ES5#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 LT1937ES5#TRPBF reliable?
The price and inventory of LT1937ES5#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1937ES5#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1937ES5#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1937ES5#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1937ES5#TRPBF?
LT1937ES5#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1937ES5#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 LT1937ES5#TRPBF?
For technical support, including LT1937ES5#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1937ES5#TRPBF requirements.
6.How does Aetrix verify that LT1937ES5#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1937ES5#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 LT1937ES5#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1937ES5#TRPBF?
All LT1937ES5#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1937ES5#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 LT1937ES5#TRPBF part is unused and in its original packaging.
Return procedure for LT1937ES5#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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