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Analog Devices Inc. LT1977EFE#PBF
- Part No.:
- LT1977EFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT1977EFE#PBF.pdf
- Description:
- IC REG BUCK ADJ 1.5A 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,889
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Product details
Overview
LT1977EFE#PBF from Analog Devices (formerly Linear Technology) is a high-voltage, current-mode synchronous step-down switching regulator IC designed for automotive and industrial power conversion. It operates from 3.3V to 60V input, delivers up to 1.5A peak switch current with 0.2Ω on-resistance, supports 500kHz fixed-frequency operation, and features Burst Mode® for 100µA quiescent current-enabling efficient 14V/42V automotive systems and battery-powered applications.
For engineers reviewing the LT1977EFE#PBF datasheet, LT1977EFE#PBF pinout, LT1977EFE#PBF application, or LT1977EFE#PBF equivalent, key selection considerations include its wide 3.3–60V input range, programmable Power Good flag, soft-start capability via CSS pin, load dump protection to 60V, and thermally enhanced 16-pin TSSOP package with exposed pad.
Technical Context
The LT1977EFE#PBF implements constant-frequency current-mode control with an internal 500kHz oscillator, peak-current sensing, and dual-loop regulation (error amplifier + current comparator). Its architecture enables fast transient response and stable loop compensation across wide input/output conditions.
It integrates a high-voltage NPN power switch with BOOST-driven saturation, uses external diode-based catch topology, and supports programmable PG delay via CT capacitor timing. Burst Mode® operation disables non-essential circuitry at light loads to maintain ultra-low 100µA quiescent current while preserving output regulation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.3V to 60V - supports direct connection to 42V automotive batteries and industrial 24/48V rails without pre-regulation. |
| Switch Current Limit | 1.5A peak - ensures robust overload handling while maintaining thermal safety under full duty cycle. |
| Quiescent Current | 100µA in Burst Mode - enables >10-year battery life in always-on vehicle modules (e.g., CAN gateways, telematics). |
| Switch On-Resistance | 0.2Ω - reduces conduction loss and thermal rise at 1.5A, enabling compact layout without heatsink. |
| Feedback Reference | 1.25V ±2.5% - allows precise output voltage setting (e.g., 3.3V, 5V, 12V) using standard 1% resistor dividers. |
| Power Good Threshold | Programmable via PGFB pin (88–92% of VREF) - provides flexible output monitoring for system sequencing and fault detection. |
| Thermal Range | –40°C to +125°C junction - qualified for under-hood automotive environments and industrial control cabinets. |
| Switching Frequency | 425–575kHz - enables small 10µH inductors and low-profile ceramic input capacitors (4.7–20µF). |
Pinout & Package
LT1977EFE#PBF is housed in a 16-pin thermally enhanced TSSOP package with exposed GND pad (Pin 17), requiring soldering to PCB ground plane for optimal thermal performance (θJC = 10°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (Pin 2) | Emiter of internal NPN switch | Connects to inductor node; clamped externally by catch diode; handles full switch current and negative flyback voltage. |
| VIN (Pin 4) | Collector of internal NPN switch | Primary input power path; supplies internal bias when BIAS pin is unconnected; requires low-inductance bypass to SW/GND. |
| BOOST (Pin 6) | Switch driver boost supply | Drives internal NPN base above VIN via external capacitor/diode; enables 0.2Ω RCE(SAT) and high efficiency at high input voltages. |
| CT (Pin 7) | Power Good timer control | Sources/sinks current to external capacitor to set PG delay time; clamps at 1.2V to trigger PG high-impedance state. |
| GND (Pins 8, 17) | Signal and thermal reference | Pins 8 and 17 plus exposed pad must be soldered to solid ground plane to minimize noise coupling and thermal resistance. |
| CSS (Pin 9) | Soft-start ramp control | Sets dV/dt of output during startup via capacitor to VOUT; disables when FB > 0.9V to prevent unnecessary delay in normal operation. |
| BIAS (Pin 10) | Efficiency-boost auxiliary supply | When connected to regulated output ≥3V, powers internal circuitry from VOUT instead of VIN-reducing input current and improving efficiency at high VIN/VOUT ratios. |
| VC (Pin 11) | Error amplifier output / current limit input | Directly controls peak switch current; used for loop compensation; clamped at 2.2V max to limit output current. |
| FB (Pin 12) | Output voltage feedback | Compares divider voltage against 1.25V reference; triggers frequency foldback and soft-start when <0.9V to protect during faults or brownouts. |
| PGFB (Pin 13) | Power Good threshold input | Resistive divider from VOUT sets PG activation point (88–92% of 1.25V); enables system-level power sequencing and fault reporting. |
| SYNC (Pin 14) | External clock synchronization | Accepts logic-level signal (30–70% duty, ≤700kHz); disabled during frequency foldback to avoid interference with protection modes. |
| SHDN (Pin 15) | Enable/disable control | Logic-high (>1.3V) enables regulation; logic-low (<1.15V) reduces input current to <1µA for deep sleep or system-level power gating. |
| PG (Pin 16) | Power Good open-drain flag | Active-low output (200µA sink) indicating valid VOUT; high-impedance when CT clamp is active-supports wired-OR fault signaling. |
Key Features
| Feature | Design Value |
|---|---|
| Burst Mode® Operation | Maintains 100µA no-load IQ across full input range, enabling multi-year operation in always-on automotive modules without compromising regulation. |
| Load Dump Protection | Withstands 60V transients on VIN-meets ISO 7637-2 Pulse 5a requirements for 12V/24V automotive systems without external TVS. |
| Programmable Power Good | Configurable PG delay and threshold via external CT capacitor and PGFB resistor divider-supports custom power-up sequencing in multi-rail systems. |
| BOOST-Driven Saturation | Uses external boost capacitor/diode to fully saturate internal NPN switch, achieving 0.2Ω RCE(SAT) and minimizing conduction loss at high input voltages. |
| Current-Mode Control | Provides inherent cycle-by-cycle current limiting, fast transient response, and simplified loop compensation-critical for dynamic load applications like infotainment processors. |
| Thermally Enhanced TSSOP | 16-pin TSSOP with exposed GND pad achieves θJA = 45°C/W-enables 1.5A continuous output in compact layouts without forced air or heatsinks. |
Applications
| Automotive Body Control Module (BCM) | Industrial PLC I/O Power Supply |
|---|---|
Use Scenario: Regulating 12V battery to 3.3V/5V for microcontroller, CAN transceiver, and sensor interface circuits in door modules or lighting controllers. IC Role / Device Role / Timing Role: Primary buck converter providing isolated, low-noise, and load-dump-protected DC-DC conversion with programmable PG for safe MCU boot sequencing. Use Value: Eliminates need for external TVS and discrete enable logic; 100µA IQ extends battery life during vehicle sleep mode; 60V tolerance avoids fuse blowing during alternator load dump events. | Use Scenario: Generating 5V rail from 24V industrial bus to power digital I/O isolators, ADCs, and fieldbus communication ICs in programmable logic controllers. IC Role / Device Role / Timing Role: High-reliability step-down regulator delivering stable 5V output under wide temperature (-40°C to +125°C) and noisy EMI environments. Use Value: 0.2Ω switch RCE(SAT) minimizes heat generation in sealed enclosures; current-mode control rejects line/load transients from motor drives; SYNC pin allows synchronization to master clock to reduce system EMI. |
| 42V Mild Hybrid Vehicle DC-DC Converter | Portable Test Equipment Power Management |
Use Scenario: Converting 42V starter-generator output to 12V for legacy vehicle subsystems in 48V mild hybrid architectures. IC Role / Device Role / Timing Role: High-input-voltage buck regulator operating in continuous conduction mode with burst-mode fallback during idle periods. Use Value: 60V absolute max rating accommodates 42V system transients; 500kHz switching enables compact magnetics; BIAS pin connection to 12V output improves efficiency by >3% at 42VIN/12VOUT. | Use Scenario: Providing regulated 3.3V and 5V rails from Li-ion battery (3.0–4.2V) or USB-C PD input (5–20V) in handheld oscilloscopes and multimeters. IC Role / Device Role / Timing Role: Wide-input buck controller supporting both battery and adapter operation with seamless transition and low quiescent current. Use Value: 3.3V minimum input enables operation down to nearly depleted battery; 100µA IQ extends runtime in battery-only mode; soft-start prevents inrush into large display capacitors. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-voltage buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3639EMSE#PBF | 40V max input, 1.2A output, integrated MOSFETs, 3mm × 4mm MSOP; lacks BOOST pin and load dump tolerance. | Best for space-constrained, lower-voltage industrial sensors where 60V tolerance is unnecessary. | Select LTC3639 when board area is critical and input stays below 40V; avoid for automotive 42V or load dump scenarios. |
| LM5164QPWPRQ1 | 65V max input, 1A output, integrated high-side FET, 500kHz, AEC-Q100 Grade 1; no programmable PG or BIAS pin. | Optimized for automotive infotainment power rails requiring AEC-Q100 qualification but less demanding on PG flexibility. | Choose LM5164Q1 for AEC-Q100-compliant designs needing higher VIN headroom; use LT1977EFE#PBF when programmable PG, BIAS, and 1.5A are required. |
Compared with LTC3639EMSE#PBF and LM5164QPWPRQ1, the LT1977EFE#PBF uniquely combines 60V input tolerance, 1.5A capability, programmable Power Good, and BIAS-assisted efficiency-making it the preferred choice for high-reliability 14V/42V automotive body electronics and industrial systems requiring design flexibility and long-term supply stability.
Availability
LT1977EFE#PBF is available at Aetrix Electronics and suitable for automotive body control modules, industrial PLC power supplies, 42V mild hybrid DC-DC converters, and portable test equipment requiring stable component supply across extended temperature and voltage ranges.
Supply support for LT1977EFE#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 automotive, industrial, communications, and healthcare markets.
The LT1977 product line was developed specifically for high-input-voltage DC-DC conversion in harsh environments-targeting automotive, industrial, and battery-powered systems where wide VIN range, low IQ, and robust transient protection are essential.
FAQ
What is the maximum input voltage rating for the LT1977EFE#PBF?
The LT1977EFE#PBF has an absolute maximum input voltage rating of 60V on the VIN pin, and it is specifically designed to withstand automotive load dump transients up to that level. Its operational input range is specified from 3.3V to 60V, making it suitable for 12V, 24V, and 42V automotive systems as well as industrial 48V distributed power rails. Exceeding 60V risks permanent damage per Absolute Maximum Ratings.
Does the LT1977EFE#PBF require an external catch diode, and why?
Yes, the LT1977EFE#PBF requires an external catch diode connected between SW and GND. Because it integrates an NPN bipolar transistor as the main switch-not a synchronous MOSFET-it cannot conduct reverse current during the off-time. The external diode provides the return path for inductor current, enabling proper buck operation. Diodes such as the Diodes Inc. B1100 are recommended per the datasheet for optimal forward voltage and recovery performance.
How does the BIAS pin improve efficiency in the LT1977EFE#PBF?
The BIAS pin on the LT1977EFE#PBF allows the IC's internal circuitry to draw operating current from the regulated output (≥3V) rather than the high-voltage input rail. When connected to VOUT, it reduces input supply current-especially beneficial at high VIN/VOUT ratios (e.g., 42V→5V), where efficiency gains of >3% are typical. This feature directly lowers power loss and thermal stress in high-input-voltage applications.
Can the LT1977EFE#PBF be synchronized to an external clock, and what are the limits?
Yes, the LT1977EFE#PBF supports external synchronization via the SYNC pin, which accepts logic-level inputs (30–70% duty cycle) from 425kHz up to 700kHz. Synchronization is disabled automatically when FB voltage falls below 0.9V (e.g., during short-circuit or brownout), ensuring protection modes remain unaffected. This capability enables EMI reduction in multi-converter systems by aligning switching edges.
What thermal management is required for the LT1977EFE#PBF in 1.5A continuous operation?
For 1.5A continuous output, the LT1977EFE#PBF requires soldering of both Pin 8 (GND) and the exposed pad (Pin 17) to a minimum 1-in² copper ground plane to achieve θJA ≈ 45°C/W. Without proper thermal land, junction temperature can exceed 125°C under full load at +85°C ambient. The datasheet specifies θJC(PAD) = 10°C/W-so direct thermal coupling to the PCB ground plane is mandatory for reliable operation.
LT1977EFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3V
- Voltage - Input (Max):
- 60V
- Voltage - Output (Min/Fixed):
- 1.25V
- Voltage - Output (Max):
- 55.2V
- Current - Output:
- 1.5A (Switch)
- Frequency - Switching:
- 500kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP-EP
LT1977EFE#PBF FAQ
1.How can I place an order for LT1977EFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1977EFE#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 LT1977EFE#PBF reliable?
The price and inventory of LT1977EFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1977EFE#PBF is usually 5 days.
3.What payment methods are accepted for LT1977EFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1977EFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1977EFE#PBF?
LT1977EFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1977EFE#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 LT1977EFE#PBF?
For technical support, including LT1977EFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1977EFE#PBF requirements.
6.How does Aetrix verify that LT1977EFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT1977EFE#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 LT1977EFE#PBF meets industry standards.
7.What is the process for return or replacement of LT1977EFE#PBF?
All LT1977EFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1977EFE#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 LT1977EFE#PBF part is unused and in its original packaging.
Return procedure for LT1977EFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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