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Analog Devices Inc. LT1946AEMS8E#PBF
- Part No.:
- LT1946AEMS8E#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT1946AEMS8E#PBF.pdf
- Description:
- IC REG BST SEPIC ADJ 1.5A 8MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:395
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Product details
Overview
LT1946AEMS8E#PBF from Analog Devices (formerly Linear Technology) is a fixed-frequency, current-mode step-up DC/DC converter IC with an integrated 1.5A, 36V NPN switch, 2.7MHz switching frequency, and adjustable output up to 35V. It delivers 12V at 430mA from a 5V input and is engineered for TFT-LCD bias supplies requiring compact, low-profile power solutions.
For engineers reviewing the LT1946AEMS8E#PBF datasheet, LT1946AEMS8E#PBF pinout, LT1946AEMS8E#PBF application, or LT1946AEMS8E#PBF equivalent, key selection criteria include its 2.7MHz operation enabling sub-1.1mm height designs, internal/external loop compensation flexibility, soft-start control via external capacitor, 1.25V feedback reference, and thermally enhanced 8-lead MSOP package with exposed ground pad.
Technical Context
The LT1946AEMS8E#PBF employs constant-frequency current-mode control with a 2.7MHz oscillator and built-in frequency foldback (reducing to 0.85MHz when FB < 0.5V) for stable start-up. Its error amplifier (transconductance = 40 µmhos, gain = 300 V/V) drives the VC pin to regulate peak switch current against a 1.25V reference.
Switching is governed by PWM comparator A2 comparing sensed switch current + ramp against the VC voltage. Current limiting (nominal 2.1A) is independent of duty cycle and acts as hard clamp. Soft-start is implemented by sourcing 4µA from the SS pin to charge an external capacitor, directly limiting VC slew rate and thus peak switch current during startup.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Rating | 1.5A continuous, 36V collector-emitter breakdown - supports high-voltage boost topologies with robust overcurrent protection. |
| Switching Frequency | 2.7MHz typical - enables use of ≤2.2µH inductors and low-ESR ceramic capacitors for ultra-low-profile (<1.1mm) PCB layouts. |
| Feedback Reference | 1.25V ±2% - sets output voltage via resistive divider (VOUT = 1.25 × (1 + R1/R2)); stable over –40°C to 85°C. |
| Quiescent Current | 5mA typical (active), 1µA max (shutdown) - minimizes standby power loss in battery-powered GPS and DSL modem applications. |
| Soft-Start Control | 4µA constant current source on SS pin - allows precise control of input current ramp rate using external capacitor (e.g., 100nF → ~375ms rise to 1.5V). |
| Thermal Resistance | θJA = 40°C/W, θJC = 10°C/W - exposed pad must be soldered to PCB ground plane to achieve rated 125°C junction temperature. |
| Operating Voltage Range | 2.6V to 16V input - compatible with single-cell Li-ion (3.0–4.2V), 3.3V, and 5V rails without pre-regulation. |
Pinout & Package
LT1946AEMS8E#PBF is housed in an 8-lead plastic MSOP (MS8E) package with exposed thermal pad (pin 4 and pad both GND). The package measures 3.00mm × 3.00mm × 1.10mm max and requires soldering the exposed pad to a local ground plane with multiple vias for thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VC (1) | Error amplifier output | Drives compensation network; short to COMP for internal compensation; external RC from VC to GND sets loop stability. |
| FB (2) | Feedback input | Connects to resistive divider tap; 1.25V reference sets regulated output; trace area must be minimized to reduce noise coupling. |
| SHDN (3) | Shutdown control | Active-high logic: ≥2.4V enables, ≤0.5V disables; 32µA max bias current; must not be left floating. |
| GND (4) | Power and signal ground | Pin 4 and exposed pad are common ground; pad must be soldered and connected via multiple vias to maximize heat dissipation. |
| SW (5) | Switch collector | High-slew-rate node; connects to inductor and Schottky diode anode; trace area must be minimized to limit EMI radiation. |
| VIN (6) | Input supply | Accepts 2.6V–16V; requires local 2.2µF ceramic bypass capacitor placed adjacent to pin. |
| COMP (7) | Internal compensation | Internally connects to 120kΩ resistor and 90pF capacitor; tie to VC for internal compensation; tie to GND if unused. |
| SS (8) | Soft-start timing | Sources 4µA to external capacitor; voltage ramp on SS controls VC slew rate and thus peak switch current during startup. |
Key Features
| Feature | Design Value |
|---|---|
| 2.7MHz fixed-frequency operation | Enables use of 2.2µH inductors and 2.2µF ceramic capacitors, reducing solution footprint and height to under 1.1mm. |
| Integrated 1.5A/36V NPN switch | Eliminates external transistor and drive circuitry; VCE(SAT) = 340mV max at 1.5A reduces conduction loss in high-current boost stages. |
| Flexible compensation architecture | Supports both internal (VC–COMP short) and external (RC–CC from VC to GND) loop compensation for optimized transient response with low-ESR ceramics. |
| Programmable soft-start | 4µA current source on SS pin allows precise control of inrush current and output voltage ramp time via external capacitor value. |
| Frequency foldback during start-up | Reduces switching frequency to 0.85MHz when FB < 0.5V, lowering minimum duty cycle and improving control of peak switch current during light-load startup. |
Applications
| TFT-LCD Bias Supply | GPS Receiver Power |
|---|---|
Use Scenario: Generating +10V, –10V, and +20V rails for active matrix TFT-LCD panels in portable medical displays and industrial HMIs. IC Role / Device Role / Timing Role: Primary step-up controller in triple-output SEPIC or cascade configuration; regulates AVDD, VON, and VOFF with independent feedback networks. Use Value: 2.7MHz operation and MS8E package enable full bias supply solution under 1.1mm height-critical for slim handheld enclosures. | Use Scenario: Providing stable 3.3V or 5V rail from single-cell Li-ion (3.0–4.2V) in compact GPS modules with aggressive size constraints. IC Role / Device Role / Timing Role: High-efficiency boost converter delivering up to 430mA; operates across full battery discharge curve with >75% efficiency at 200mA load. Use Value: 1µA shutdown current and 5mA quiescent current extend battery life; soft-start prevents GPS RF section disruption during power-on. |
| DSL Modem Local Supply | Industrial Sensor Node Power |
Use Scenario: Generating isolated 12V bias for line-driver amplifiers and 3.3V for PHY/MAC in residential DSL modems with strict EMI limits. IC Role / Device Role / Timing Role: Primary DC/DC stage converting 5V USB or wall-adapter input to 12V; operates at 2.7MHz to shift noise spectrum above sensitive ADSL bands. Use Value: Low EMI due to fixed frequency and small passive components; integrated switch eliminates layout-sensitive gate-drive routing. | Use Scenario: Powering low-power microcontrollers, analog front-ends, and wireless transceivers (e.g., LoRa, BLE) from 3.3V or 5V rails in edge sensor nodes. IC Role / Device Role / Timing Role: Compact, efficient boost stage extending usable input range down to 2.6V while maintaining regulated 3.3V output under dynamic load. Use Value: MS8E package and ceramic-only BOM simplify automated assembly; –40°C to 85°C rating ensures reliability in uncontrolled environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-up DC/DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3531EMS8E#PBF | 2.2MHz switching, 1.25A switch, 30V max, 1.215V feedback, no frequency foldback | Lower max switch current and voltage; lacks foldback for demanding start-up conditions | Choose for lower EMI sensitivity where 1.25A output suffices and foldback is unnecessary. |
| LT3467EMS8E#PBF | 1.3MHz switching, 1.3A switch, 40V max, 1.25V feedback, integrated soft-start but no foldback | Slower switching requires larger inductors/caps; higher VSW rating suits 36V+ inputs | Prefer when input exceeds 16V or board height >1.1mm is acceptable; avoid for ultra-low-profile TFT designs. |
Compared with LTC3531EMS8E#PBF and LT3467EMS8E#PBF, the LT1946AEMS8E#PBF offers superior combination of 2.7MHz speed for minimal passive size, 1.5A/36V switch robustness, and dual-stage start-up control (foldback + soft-start), making it uniquely suited for space-constrained TFT-LCD and portable RF applications.
Availability
LT1946AEMS8E#PBF is available at Aetrix Electronics and suitable for TFT-LCD bias supplies, GPS receiver power management, DSL modem local regulation, and industrial sensor node designs requiring stable component supply with guaranteed long-term availability.
Supply support for LT1946AEMS8E#PBF 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 precision analog and power management portfolio. Linear pioneered high-performance DC/DC converters with integrated power switches and advanced control architectures.
The LT1946AEMS8E#PBF belongs to Linear's high-frequency boost converter product line, designed specifically for space-constrained applications like portable displays and communications equipment where low profile, fast transient response, and reliable start-up are critical.
FAQ
What is the maximum output voltage achievable with the LT1946AEMS8E#PBF?
The LT1946AEMS8E#PBF supports adjustable output voltages from VIN up to 35V, as confirmed in the "Features" section of the datasheet. This is enabled by its 36V-rated internal NPN switch and 1.25V feedback reference, allowing VOUT = 1.25 × (1 + R1/R2) scaling. Output stability and efficiency depend on proper selection of external components-including Schottky diode voltage rating, inductor saturation current, and output capacitor voltage rating-as detailed in Application Note 1946A TA01.
Does the LT1946AEMS8E#PBF require external compensation components?
The LT1946AEMS8E#PBF supports both internal and external compensation. Tying the VC pin to the COMP pin enables internal compensation (using built-in 120kΩ and 90pF), while connecting an RC network from VC to GND provides external control for optimizing transient response-especially with low-ESR ceramic output capacitors. The datasheet recommends starting with CC = 270pF and RC = 27.4kΩ for the 5V-to-12V/430mA reference design, and adjusting RC with a potentiometer while observing transient waveforms.
How is soft-start configured on the LT1946AEMS8E#PBF?
Soft-start on the LT1946AEMS8E#PBF is controlled by an external capacitor connected to the SS (pin 8) terminal. A constant 4µA current charges this capacitor; when its voltage reaches 1.5V, full regulation begins. For example, a 100nF capacitor yields ~375ms ramp time (1.5V / 4µA = 375ms). Leaving SS open disables soft-start. The SS pin directly limits the slew rate of the VC pin, thereby controlling peak switch current during startup and preventing inrush-related stress on input sources and output capacitors.
What thermal considerations apply to the LT1946AEMS8E#PBF MS8E package?
The LT1946AEMS8E#PBF uses an 8-lead MSOP with exposed thermal pad (pin 4 and pad share GND). To achieve the specified θJA = 40°C/W and operate reliably at 125°C junction temperature, the exposed pad must be soldered to a large local ground plane and connected via ≥4 thermal vias (0.3mm diameter) to an internal or backside ground layer. Layout guidelines emphasize wide copper pours and minimizing trace length between pin 4 and the pad, as insufficient thermal relief causes premature thermal shutdown or parametric drift under sustained 430mA loads.
Can the LT1946AEMS8E#PBF be used in SEPIC topology configurations?
Yes-the LT1946AEMS8E#PBF is explicitly validated in SEPIC topology for triple-output TFT-LCD supplies, as shown in datasheet Figures TA09 and TA05. Its current-mode control, 36V switch rating, and ability to regulate outputs both above and below VIN make it suitable for SEPIC implementations requiring output disconnect capability and wide input/output differentials. External component selection (e.g., two coupled inductors, appropriate diodes) must follow Linear's application guidance to maintain stability and efficiency.
LT1946AEMS8E#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width) Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Up, Step-Up/Step-Down
- Output Configuration:
- Positive
- Topology:
- Boost, SEPIC
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.45V
- Voltage - Input (Max):
- 16V
- Voltage - Output (Min/Fixed):
- 2.45V
- Voltage - Output (Max):
- 35V
- Current - Output:
- 1.5A (Switch)
- Frequency - Switching:
- 2.7MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-MSOP-EP
LT1946AEMS8E#PBF FAQ
1.How can I place an order for LT1946AEMS8E#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1946AEMS8E#PBF 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 LT1946AEMS8E#PBF reliable?
The price and inventory of LT1946AEMS8E#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1946AEMS8E#PBF is usually 5 days.
3.What payment methods are accepted for LT1946AEMS8E#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1946AEMS8E#PBF transactions.
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4.How is shipping managed for LT1946AEMS8E#PBF?
LT1946AEMS8E#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1946AEMS8E#PBF 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 LT1946AEMS8E#PBF?
For technical support, including LT1946AEMS8E#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1946AEMS8E#PBF requirements.
6.How does Aetrix verify that LT1946AEMS8E#PBF is sourced from the original manufacturer or authorized distributors?
All LT1946AEMS8E#PBF 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 LT1946AEMS8E#PBF meets industry standards.
7.What is the process for return or replacement of LT1946AEMS8E#PBF?
All LT1946AEMS8E#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1946AEMS8E#PBF, 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 LT1946AEMS8E#PBF part is unused and in its original packaging.
Return procedure for LT1946AEMS8E#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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