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Analog Devices Inc. LT1946EMS8#PBF
- Part No.:
- LT1946EMS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LT1946EMS8#PBF.pdf
- Description:
- IC REG BOOST ADJ 1.5A 8MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:157
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Product details
Overview
LT1946EMS8#PBF from Analog Devices (formerly Linear Technology) is a fixed-frequency, current-mode step-up DC/DC converter with an integrated 1.5A, 36V NPN switch. It delivers 8V at 430mA from a 3.3V input, features 1.2MHz switching, internal soft-start control via external capacitor, and supports output voltages up to 34V - optimized for TFT-LCD bias supplies and compact local power rails.
For engineers reviewing the LT1946EMS8#PBF datasheet, LT1946EMS8#PBF pinout, LT1946EMS8#PBF application, or LT1946EMS8#PBF equivalent, key selection considerations include its 1.2MHz constant-frequency operation, 1.25V feedback reference, 8-lead MSOP package with exposed pad option, soft-start timing control via SS pin, and compatibility with low-ESR ceramic output capacitors in space-constrained designs.
Technical Context
The LT1946EMS8#PBF employs a current-mode control architecture with a 1.2MHz oscillator and frequency foldback (to 400kHz) when FB voltage drops below 0.5V, improving startup stability. Its error amplifier (transconductance = 40 µmhos, gain = 300 V/V) drives the VC pin to regulate peak switch current, while internal compensation is enabled by shorting VC to COMP.
Switch current limiting is fixed at 1.5A (typ), with VCE(SAT) = 240 mV (typ) at 1A. Soft-start is implemented by sourcing 4 µA from the SS pin to charge an external capacitor; the resulting ramp directly limits VC voltage rise and thus peak switch current during startup.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 1.5A typical - ensures robust overcurrent protection without external sensing |
| Feedback Reference Voltage | 1.250V ±20mV - sets precise output voltage via R1/R2 divider (VOUT = 1.25 × (1 + R1/R2)) |
| Switching Frequency | 1.2MHz typical - enables use of small 4.7µH inductors and low-value ceramic capacitors |
| Input Voltage Range | 2.45V to 16V - supports single-cell Li-ion, 3.3V, and 5V rail inputs |
| Output Voltage Range | Up to 34V - suitable for high-voltage TFT-LCD AVDD, VON, and VOFF generation |
| Quiescent Current | 3.2mA typical (active), 0.1µA typical (shutdown) - minimizes standby power loss |
| Soft-Start Charging Current | 4µA typical - allows predictable, adjustable startup current ramp via external SS capacitor |
Pinout & Package
LT1946EMS8#PBF is housed in an 8-lead plastic MSOP package (MS8) with no exposed pad. The package measures 3.0mm × 3.0mm × 1.1mm max height and is RoHS-compliant and lead-free (#PBF).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VC (Pin 1) | Error amplifier output | Connects to external compensation network; short to COMP for internal compensation |
| FB (Pin 2) | Feedback input | Monitors output via resistive divider; 1.25V reference sets regulation point |
| SHDN (Pin 3) | Shutdown control | Active-high enable: ≥2.4V enables, ≤0.5V disables; must not be left floating |
| GND (Pin 4) | Power ground | Primary return path for switch, IC core, and compensation; tie directly to local ground plane |
| SW (Pin 5) | Switch collector | High-current node connecting internal NPN switch to external inductor/diode; minimize trace area to reduce EMI |
| VIN (Pin 6) | Input supply | Accepts 2.45V–16V; requires local 2.2µF ceramic bypass capacitor placed adjacent to pin |
| COMP (Pin 7) | Internal compensation | Provides access to internal 120kΩ resistor and 90pF capacitor; tie to VC for internal loop compensation |
| SS (Pin 8) | Soft-start control | Sources 4µA to external capacitor; voltage ramp on SS controls VC ramp rate and startup current slew |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 1.5A, 36V NPN switch | Eliminates external transistor and reduces BOM count; VCE(SAT) = 240 mV @ 1A enables high efficiency at medium loads |
| 1.2MHz fixed-frequency operation | Enables use of sub-5mm footprint inductors (e.g., TDK RLF5018T-4R7M1R4) and 10µF-class ceramic output caps |
| External soft-start capacitor control | 4µA SS pin current allows precise tuning of inrush current and output voltage rise time without firmware or extra ICs |
| Flexible compensation options | Supports both internal (VC–COMP short) and external (RC/CC network from COMP to GND) loop compensation for transient optimization |
| Frequency foldback at light load/startup | Reduces oscillator frequency to 400kHz when FB < 0.5V, improving controllability and reducing minimum duty cycle limitations |
Applications
| TFT-LCD Panel Bias Supply | GPS Receiver Power Rail |
|---|---|
|
Use Scenario: Generating AVDD (8V), VON (23V), and VOFF (–8V) for active-matrix LCD displays in portable instrumentation. IC Role / Device Role / Timing Role: Primary boost controller delivering regulated high-voltage rails from a 3.3V system bus. Use Value: 1.2MHz operation and MSOP package enable <1.2mm profile solutions; 34V max output supports wide-range TFT bias requirements. |
Use Scenario: Providing stable 3.3V-to-5V or 3.3V-to-8V local supply for GPS baseband ICs and RF front-end components. IC Role / Device Role / Timing Role: Compact, efficient step-up regulator powering noise-sensitive analog and mixed-signal blocks. Use Value: Low quiescent current (3.2mA) and fast transient response preserve battery life and maintain signal integrity under dynamic load changes. |
| DSL Modem Line Driver Supply | Industrial Local Power Management |
|
Use Scenario: Generating 12V rail for line driver amplifiers in ADSL/VDSL modems operating from 3.3V or 5V backplane. IC Role / Device Role / Timing Role: High-efficiency boost converter driving moderate-current analog circuitry with tight ripple tolerance. Use Value: 430mA output capability at 8V and 275mA at 12V meets line driver peak demands; ceramic-capacitor compatible design minimizes EMI. |
Use Scenario: Creating isolated auxiliary rails (e.g., 5V, ±12V) in programmable logic controllers and sensor interface modules. IC Role / Device Role / Timing Role: Flexible, externally compensated DC/DC building block for multi-rail industrial subsystems. Use Value: Dual compensation modes (internal/external) and wide VIN range (2.45–16V) simplify design across varied input sources and load profiles. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar boost converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1946EMS8E#PBF | Same die, but in MS8E package with exposed thermal pad (Pin 9 = GND); θJA = 125°C/W (4-layer board) vs. 40°C/W for MS8 | Better thermal performance in high-power or high-ambient environments; requires soldering exposed pad to PCB ground plane | Select LT1946EMS8E#PBF when thermal dissipation exceeds 0.5W or ambient temperature exceeds 70°C |
| LT1946AEMS8E#PBF | 2.7MHz switching frequency, same 1.5A switch; higher frequency enables smaller inductors (e.g., 2.2µH) and faster transient response | Higher switching losses at full load; reduced output capacitance requirement (e.g., 4.7µF instead of 20µF) | Choose LT1946AEMS8E#PBF for ultra-compact layouts where size is critical and efficiency at 430mA is secondary to footprint reduction |
Compared with LT1946EMS8#PBF, the LT1946EMS8E#PBF improves thermal handling via its exposed pad but requires additional PCB layout effort, while the LT1946AEMS8E#PBF trades higher-frequency operation for increased switching loss - making the original LT1946EMS8#PBF optimal for balanced efficiency, size, and thermal simplicity in mainstream TFT-LCD and DSL applications.
Availability
LT1946EMS8#PBF is available at Aetrix Electronics and suitable for TFT-LCD bias supplies, GPS receiver power rails, and DSL modem line driver circuits requiring stable component supply, long-term manufacturability, and consistent parametric performance across production lots.
Supply support for LT1946EMS8#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 legacy precision analog and power management portfolio. Linear was founded in 1981 and pioneered high-performance switching regulators for demanding industrial and communications applications.
The LT1946EMS8#PBF belongs to Linear's high-frequency, integrated-switch boost converter product line, designed specifically for space-constrained, high-voltage bias generation in display, telecom, and portable electronics - emphasizing low-profile packaging, external component flexibility, and robust startup behavior.
FAQ
What is the maximum output voltage achievable with the LT1946EMS8#PBF?
The LT1946EMS8#PBF supports output voltages up to 34V, as confirmed by Absolute Maximum Ratings and Typical Performance Characteristics. This is achieved using an external resistive feedback divider (R1/R2) referenced to the 1.25V internal bandgap. Output stability and regulation accuracy depend on proper compensation and low-ESR output capacitance, especially above 20V.
Can the LT1946EMS8#PBF operate from a 2.5V input source?
No - the LT1946EMS8#PBF has a minimum operating input voltage of 2.45V (typical) and 2.6V (guaranteed), so 2.5V falls within the marginal region and may result in unreliable startup or regulation. For reliable operation, VIN must be ≥2.6V across temperature and process variation; 2.7V or higher is recommended for margin.
How does the soft-start function work on the LT1946EMS8#PBF?
The LT1946EMS8#PBF sources a precise 4µA current from the SS pin during startup. An external capacitor connected between SS and GND integrates this current, generating a linear voltage ramp. This ramp directly controls the VC pin voltage, thereby limiting peak switch current and preventing inrush - typical SS capacitor values range from 10nF to 200nF.
Is the LT1946EMS8#PBF pin-compatible with the LT1946AEMS8E#PBF?
No - although both share functional similarity, the LT1946EMS8#PBF uses an 8-lead MS8 package without an exposed pad, while the LT1946AEMS8E#PBF uses the MS8E package with Pin 9 (exposed pad) tied to GND. Their pinouts differ: MS8E adds thermal pad connectivity and is not mechanically or electrically interchangeable without PCB redesign.
What type of diode is recommended for use with the LT1946EMS8#PBF?
A Schottky diode is required due to its low forward voltage and fast recovery. The Microsemi UPS120 (or equivalent) is explicitly recommended in the datasheet for ≤20V VIN-to-VOUT differentials. For higher differential applications (e.g., 3.3V-to-34V), the UPS140 (40V-rated) is specified. Diode average current rating must exceed peak inductor current, typically ≥1A.
LT1946EMS8#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Up
- Output Configuration:
- Positive
- Topology:
- Boost
- 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):
- 34V
- Current - Output:
- 1.5A (Switch)
- Frequency - Switching:
- 1.2MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-MSOP
LT1946EMS8#PBF FAQ
1.How can I place an order for LT1946EMS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1946EMS8#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 LT1946EMS8#PBF reliable?
The price and inventory of LT1946EMS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1946EMS8#PBF is usually 5 days.
3.What payment methods are accepted for LT1946EMS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1946EMS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1946EMS8#PBF?
LT1946EMS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1946EMS8#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 LT1946EMS8#PBF?
For technical support, including LT1946EMS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1946EMS8#PBF requirements.
6.How does Aetrix verify that LT1946EMS8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1946EMS8#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 LT1946EMS8#PBF meets industry standards.
7.What is the process for return or replacement of LT1946EMS8#PBF?
All LT1946EMS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1946EMS8#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 LT1946EMS8#PBF part is unused and in its original packaging.
Return procedure for LT1946EMS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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