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Analog Devices Inc. LT1946EMS8E#PBF
- Part No.:
- LT1946EMS8E#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT1946EMS8E#PBF.pdf
- Description:
- IC REG BOOST ADJ 1.5A 8MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,042
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Product details
Overview
LT1946EMS8E#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, operates at 1.2MHz switching frequency, features internal/external loop compensation, and includes programmable soft-start via external capacitor. It is engineered for TFT-LCD bias supplies requiring compact, high-efficiency boost conversion.
For engineers reviewing the LT1946EMS8E#PBF datasheet, LT1946EMS8E#PBF pinout, LT1946EMS8E#PBF application, or LT1946EMS8E#PBF equivalent, key selection considerations include its 1.2MHz operation enabling small inductors/ceramic capacitors, 1.25V feedback reference, 8-lead MSOP-E package with exposed ground pad, and soft-start control via SS pin current sourcing (4µA typical).
Technical Context
The LT1946EMS8E#PBF employs constant-frequency current-mode control with a 1.2MHz oscillator and foldback to 0.4MHz during startup when FB < 0.5V. Its error amplifier (transconductance = 40 µmhos, gain = 300 V/V) drives the VC pin to regulate peak switch current, while the internal 1.5A switch exhibits 340mV VCE(SAT) at 1A.
Loop compensation is flexible: internal (VC tied to COMP) or external (RC network from COMP to GND). Soft-start is implemented by sourcing 4µA from the SS pin to charge an external capacitor, directly limiting VC ramp rate and thus peak switch current during startup.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 1.2 MHz typical; enables use of ≤5.4µH inductors and low-ESR ceramic capacitors for ultra-low-profile designs. |
| Internal Switch Rating | 1.5A continuous, 36V breakdown; supports output voltages up to 34V with robust overcurrent protection. |
| Feedback Reference | 1.250 V ±20 mV; sets output voltage via external resistor divider (VOUT = 1.25 × (1 + R1/R2)). |
| Soft-Start Current | 4 µA typical sourced from SS pin; determines startup slew rate and inrush current control via external capacitor. |
| Quiescent Current | 5 mA typical in operation; ensures low standby power loss in battery-sensitive applications like GPS receivers. |
| Operating Input Range | 2.6 V to 16 V; supports single-cell Li-ion (3.3V), dual-cell alkaline, and industrial 5V/12V rails. |
| Output Voltage Range | Up to 34 V; validated for 8V/430mA, 12V/275mA, and triple-output TFT-LCD supplies (e.g., +8V/–8V/23V). |
Pinout & Package
LT1946EMS8E#PBF uses an 8-lead plastic MSOP package with exposed ground pad (Pin 9), requiring soldering to PCB for thermal and electrical performance. Thermal resistance θJA = 125°C/W (4-layer board), θJC = 10°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VC (Pin 1) | Error amplifier output | Drives compensation network; connects to external RC or shorted to COMP for internal compensation. |
| FB (Pin 2) | Feedback input | High-impedance node sensing resistive divider; 1.25V reference enables precise output regulation. |
| SHDN (Pin 3) | Shutdown control | Active-high enable: ≥2.4V enables, ≤0.5V disables; sinks <0.1µA in shutdown for ultra-low leakage. |
| GND (Pin 4) | Power ground | Primary return path; must tie directly to local ground plane with low-inductance connection. |
| SW (Pin 5) | Switch collector | High-current, high-dV/dt node; requires minimized trace area to reduce EMI and switching losses. |
| VIN (Pin 6) | Input supply | Accepts 2.6–16V; requires local 2.2µF ceramic bypass capacitor placed adjacent to pin. |
| COMP (Pin 7) | Compensation access | Provides internal 120kΩ/90pF network; tie to VC for internal comp or to RC network for external tuning. |
| SS (Pin 8) | Soft-start control | Sources 4µA to external capacitor; voltage ramp on SS limits VC rise and controls startup current slew. |
| Exposed Pad (Pin 9) | Thermal & electrical ground | Mandatory solder connection to PCB ground plane for thermal dissipation and noise reduction. |
Key Features
| Feature | Design Value |
|---|---|
| 1.2MHz fixed-frequency operation | Enables use of sub-6µH ferrite inductors and 10µF-class ceramic output capacitors, reducing solution height to <1.2mm. |
| Integrated 1.5A, 36V NPN switch | Eliminates external transistor; VCE(SAT) = 340mV @ 1A ensures >85% efficiency at 430mA output (3.3V→8V). |
| Programmable soft-start | 4µA current source on SS pin allows precise control of input current ramp rate, preventing inrush-induced supply droop. |
| Dual compensation architecture | Supports either internal (VC–COMP short) or external (RC from COMP to GND) loop tuning for optimal transient response with low-ESR ceramics. |
| Frequency foldback at startup | Oscillator reduces to 0.4MHz when FB < 0.5V, lowering minimum duty cycle and improving controllability during output voltage build-up. |
Applications
| TFT-LCD Panel Bias Supply | GPS Receiver Power Management |
|---|---|
|
Use Scenario: Generating +8V, –8V, and +23V rails for active matrix LCD gate/source drivers and gamma correction circuitry in portable displays. IC Role / Device Role / Timing Role: Primary boost controller providing regulated high-voltage bias from a 3.3V system rail; manages startup sequencing via SS pin. Use Value: Achieves 375mA at 8V with >75% efficiency and <1.2mm profile using 5.4µH inductor and X5R ceramics-critical for slim handheld form factors. |
Use Scenario: Stepping up 3.3V battery voltage to 12V for GPS front-end LNA and RF synthesizer bias in automotive and portable navigation units. IC Role / Device Role / Timing Role: High-frequency boost converter supplying stable 12V/275mA; leverages 1.2MHz switching to minimize EMI near sensitive RF sections. Use Value: Delivers 80%+ efficiency across 100–400mA load range while maintaining tight output regulation (<±1.5%) under dynamic GPS signal acquisition loads. |
| DSL Modem Local Power Rail | Industrial Local Boost Converter |
|
Use Scenario: Creating isolated 5V or 12V auxiliary rails from a 3.3V or 5V system supply for DSL line driver ICs and analog front-end components. IC Role / Device Role / Timing Role: Compact, high-efficiency DC/DC stage replacing discrete boost solutions; integrates soft-start to prevent upstream supply sag during modem initialization. Use Value: Reduces BOM count by 4 components vs. discrete implementation and achieves <15mVpp output ripple with 20µF X5R output capacitor. |
Use Scenario: Providing 34V maximum output for industrial sensor excitation, piezo actuator drive, or analog signal conditioning circuits operating from 5V or 12V backplanes. IC Role / Device Role / Timing Role: Robust boost controller with 36V switch rating and thermal shutdown; used with external Schottky diode (e.g., Microsemi UPS120) for reliability. Use Value: Sustains 430mA output at 34V with <100mV dropout under full load, enabled by low 340mV VCE(SAT) and exposed-pad thermal design. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar boost converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1946AEMS8E#PBF | 2.7MHz switching frequency, same 8-lead MSOP-E package; higher quiescent current (6mA) but faster transient response. | Better suited for space-constrained designs needing smaller inductors (<2.2µH); less optimal for noise-sensitive RF applications due to higher fundamental frequency. | Select LT1946AEMS8E#PBF only if board area is critical and EMI filtering can accommodate 2.7MHz harmonics. |
| LT1930AIMS5#TRPBF | 5-lead ThinSOT package, 1A switch, 1.2MHz; lacks soft-start, compensation flexibility, and exposed thermal pad. | Targeted at cost-sensitive, lower-current (≤300mA) applications where PCB area is secondary to unit cost and simplicity. | Choose LT1930AIMS5#TRPBF for fixed 12V/300mA outputs where soft-start and thermal performance are non-critical. |
Compared with LT1946EMS8E#PBF, the LT1946AEMS8E#PBF trades higher switching frequency for increased EMI sensitivity and quiescent current, while the LT1930AIMS5#TRPBF sacrifices soft-start, thermal performance, and output flexibility to achieve lower cost and smaller footprint in less demanding applications.
Availability
LT1946EMS8E#PBF is available at Aetrix Electronics and suitable for TFT-LCD bias supplies, GPS receiver power management, and DSL modem local power rails requiring stable component supply, long-term lifecycle support, and guaranteed RoHS-compliant sourcing.
Supply support for LT1946EMS8E#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving precision instrumentation, communications, and industrial markets.
The LT1946EMS8E#PBF belongs to Linear's high-frequency boost converter product line, designed specifically for compact, high-efficiency DC/DC conversion in display, portable, and telecom power applications where low profile and fast transient response are essential.
FAQ
What is the maximum output voltage achievable with the LT1946EMS8E#PBF?
The LT1946EMS8E#PBF supports output voltages up to 34V, as confirmed by Absolute Maximum Ratings (SW voltage = –0.4V to 36V) and Typical Application circuits generating +23V and +34V rails. This capability is enabled by its 36V-rated internal NPN switch and stable loop compensation up to high gain-bandwidth products.
How does the soft-start function work on the LT1946EMS8E#PBF?
The LT1946EMS8E#PBF sources a precise 4µA current from the SS pin to charge an external capacitor. The resulting voltage ramp on SS directly limits the rate of rise on the VC pin, thereby controlling peak switch current during startup. A 100nF capacitor yields ~38ms soft-start time to 1.5V, preventing input inrush and output overshoot.
Can the LT1946EMS8E#PBF operate with internal compensation only?
Yes, the LT1946EMS8E#PBF supports internal compensation by shorting the VC pin to the COMP pin. This configuration uses the internal 120kΩ resistor and 90pF capacitor, eliminating external components. It is validated in Figure 1 and suitable for standard 8V/430mA and 12V/275mA applications with moderate transient requirements.
What is the recommended diode for use with the LT1946EMS8E#PBF?
The Microsemi UPS120 Schottky diode is explicitly recommended in the LT1946EMS8E#PBF datasheet for ≤20V input-to-output differentials. For higher differentials (e.g., 34V output), the UPS140 (40V-rated) is specified. Both handle 1A average forward current and minimize conduction losses due to low VF.
Does the LT1946EMS8E#PBF require the exposed pad to be soldered?
Yes, the exposed pad (Pin 9) of the LT1946EMS8E#PBF is electrically and thermally connected to GND and must be soldered to the PCB ground plane. The datasheet states "EXPOSED PAD (PIN 9) IS GROUND (MUST BE SOLDERED TO PCB)" and specifies θJC = 10°C/W only when properly soldered-omission degrades thermal performance and may cause thermal shutdown.
LT1946EMS8E#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
- 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-EP
LT1946EMS8E#PBF FAQ
1.How can I place an order for LT1946EMS8E#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1946EMS8E#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 LT1946EMS8E#PBF reliable?
The price and inventory of LT1946EMS8E#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1946EMS8E#PBF is usually 5 days.
3.What payment methods are accepted for LT1946EMS8E#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1946EMS8E#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1946EMS8E#PBF?
LT1946EMS8E#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1946EMS8E#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 LT1946EMS8E#PBF?
For technical support, including LT1946EMS8E#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1946EMS8E#PBF requirements.
6.How does Aetrix verify that LT1946EMS8E#PBF is sourced from the original manufacturer or authorized distributors?
All LT1946EMS8E#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 LT1946EMS8E#PBF meets industry standards.
7.What is the process for return or replacement of LT1946EMS8E#PBF?
All LT1946EMS8E#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1946EMS8E#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 LT1946EMS8E#PBF part is unused and in its original packaging.
Return procedure for LT1946EMS8E#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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