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Analog Devices Inc. LT8631HFE#PBF
- Part No.:
- LT8631HFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 20-TSSOP (0.173", 4.40mm Width), 16 Leads, Exposed Pad
- Datasheet:
-
LT8631HFE#PBF.pdf
- Description:
- IC REG BUCK ADJ 1A 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:406
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Product details
Overview
LT8631HFE#PBF from Analog Devices is a 100V input, 1A synchronous step-down DC/DC regulator with peak current mode control, internal MOSFETs (775 mΩ top / 550 mΩ bottom), and low-ripple Burst Mode operation delivering 16 µA quiescent current at 12VIN→5VOUT. It supports 3V–100V input, 0.8V–60V output, and operates across –40°C to +150°C junction temperature for automotive and industrial power rails.
For engineers reviewing the LT8631HFE#PBF datasheet, LT8631HFE#PBF pinout, LT8631HFE#PBF application, or LT8631HFE#PBF equivalent, key selection criteria include its ultrawide input range, programmable 100 kHz–1 MHz switching frequency via RT resistor, ±7.5% power good flag accuracy, and thermal robustness in the 20-lead TSSOP package with exposed GND pad.
Technical Context
The LT8631HFE#PBF implements constant-frequency peak current mode control with internal synchronous switches and a dedicated BST bootstrap circuit for high-side gate drive. Its VC node regulates peak inductor current up to 2.1 A typical, while soft-start and tracking are controlled by a 4.5 µA current source on TR/SS.
Burst Mode operation activates below ~100 mA load, reducing IQ to 16 µA at 12VIN while maintaining <10 mVP-P output ripple; pulse-skipping or external synchronization is selectable via SYNC/MODE pin voltage or signal, supporting 100–1000 kHz sync range.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3 V to 100 V - supports direct connection to unregulated automotive battery (cold-crank), telecom 48 V/72 V, and industrial HV rails without pre-regulation. |
| Output Current | 1.0 A continuous - verified at 7.5 VIN and 50 VIN with 15 µH inductor; derated above 125°C per H-grade thermal spec. |
| Quiescent Current | 16 µA at 12 VIN → 5 VOUT - enables >10-year battery life in always-on IoT sensors and remote monitoring nodes. |
| Switching Frequency | 100 kHz to 1 MHz - set by RT resistor (8.66 kΩ to 187 kΩ); allows trade-off between EMI filtering size and efficiency at light loads. |
| Power Good Accuracy | ±7.5% of 0.808 V reference - provides reliable system reset and sequencing control for downstream FPGAs and microcontrollers. |
| Junction Temp Range | –40°C to +150°C - qualified for under-hood automotive, industrial motor drives, and high-ambient power supplies. |
| Feedback Reference | 0.808 V ±12 mV - enables precise output regulation with minimal drift over temperature and line/load conditions. |
Pinout & Package
The LT8631HFE#PBF is housed in a thermally enhanced 20-lead plastic TSSOP package (FE20) with exposed GND pad (Pin 21) requiring PCB soldering for thermal performance and high-voltage creepage spacing. θJA = 40°C/W, θJC(PAD) = 10°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (1) | Main power input & switch drain | Accepts 3–100 V; connects to internal high-side MOSFET drain and UVLO comparator; requires local 10 µF ceramic decoupling. |
| EN/UV (3) | Enable & undervoltage lockout input | Active-high enable with 1.19 V threshold; externally programmable UVLO using resistor divider from VIN to GND. |
| PG (5) | Open-drain power good flag | Sinks current when FB deviates >±7.5% from 0.808 V; 1.9% hysteresis prevents chatter during marginal regulation. |
| SYNC/MODE (7) | Mode selection & sync input | GND = Burst Mode; >1.5 V = pulse-skipping; external 100–1000 kHz clock = synchronized pulse-skipping. |
| RT (8) | Frequency programming | Resistor to GND sets fSW: 8.66 kΩ = 1 MHz, 19.6 kΩ = 500 kHz, 187 kΩ = 100 kHz. |
| TR/SS (10) | Soft-start & tracking control | 4.5 µA current source charges external capacitor; slope controls VOUT ramp rate and enables output voltage tracking. |
| FB (11) | Feedback input | Inverting input of error amplifier; regulated to 0.808 V; bias current ≤25 nA minimizes divider loading error. |
| VOUT (12) | Output sense & current monitor | Connects to output capacitor; internal current-sense resistor measures inductor current for peak current mode control. |
| IND (14) | Inductor connection | High-current path to external inductor; must be routed with short, low-inductance trace to minimize switching noise. |
| INTVCC (16) | Internal LDO bypass | Bypassed with 2.2 µF ceramic to GND; powers internal analog circuitry; not for external loading. |
| BST (18) | Bootstrap supply | Drives high-side gate; requires 0.1 µF ceramic capacitor between BST and SW pins placed adjacent to IC. |
| SW (20) | Switch node | Connection point of internal MOSFETs; high dI/dt node requiring minimized loop area with inductor and BST cap. |
| GND (21) | Ground reference & thermal pad | Only ground connection; exposed pad must be soldered to large copper pour for thermal and EMI performance. |
Key Features
| Feature | Design Value |
|---|---|
| Ultrawide 3V–100V Input Range | Eliminates need for pre-regulators in 24 V/48 V industrial systems and 12 V/24 V automotive applications with cold-crank tolerance. |
| Low-Ripple Burst Mode Operation | Maintains <10 mVP-P output ripple at no-load while drawing only 16 µA from VIN - critical for noise-sensitive analog and RF subsystems. |
| Programmable Undervoltage Lockout | EN/UV pin accepts resistor divider to set custom startup voltage (e.g., 5.5 V for 12 V battery systems), preventing brownout operation. |
| Flexible Output Tracking | TR/SS pin supports coordinated power-up sequencing with other regulators via shared soft-start capacitor or external voltage ramp. |
| Thermally Enhanced TSSOP Package | Exposed GND pad reduces θJA to 40°C/W and supports full 1 A output at +150°C junction temperature - validated for H-grade qualification. |
Applications
| Automotive Infotainment Power | Industrial PLC I/O Module |
|---|---|
Use Scenario: Powering FPGA, DSP, and display controllers in head units where input voltage varies from 6 V (cold crank) to 16 V (load dump). IC Role / Device Role / Timing Role: Primary 5 V/1 A buck regulator with programmable UVLO and PG flag for system-level fault reporting and safe shutdown. Use Value: 100 V absolute max rating withstands load-dump transients; ±7.5% PG accuracy ensures deterministic reset timing for safety-critical firmware. | Use Scenario: Regulating 5 V for isolated digital I/O channels in modular PLC backplanes operating in 40–85°C ambient environments. IC Role / Device Role / Timing Role: High-reliability point-of-load converter with H-grade temperature rating and low-IQ Burst Mode for standby power management. Use Value: 150°C junction rating enables operation without forced air cooling; 16 µA IQ extends battery backup runtime during AC loss events. |
| Telecom Remote Radio Unit | Medical Portable Diagnostic Device |
Use Scenario: Converting 48 V telecom supply to 3.3 V for baseband processors and ADCs in outdoor small-cell radios. IC Role / Device Role / Timing Role: Synchronous buck with 100 kHz–1 MHz programmable frequency to avoid sensitive IF bands and meet EMI compliance. Use Value: RT-resistor tuning enables optimal frequency selection for filter size vs. efficiency; low ripple preserves SNR in high-resolution data converters. | Use Scenario: Providing stable 3.3 V rail for low-power MCU, touch controller, and Bluetooth LE radio in handheld ultrasound or glucose monitors. IC Role / Device Role / Timing Role: Micropower step-down regulator with soft-start and tracking for multi-rail sequencing during battery-powered boot. Use Value: 16 µA IQ extends single-charge battery life beyond 12 months; TR/SS tracking ensures clean power-up of analog front-end before digital logic activation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3639EMSE#PBF | 60 V max input, 1.5 A output, fixed 2 MHz fSW, no SYNC input, lower IQ (4 µA) | Not suitable for >60 V inputs (e.g., 72 V telecom, load-dump automotive); lacks frequency synchronization. | Select when input stays ≤60 V and ultra-low IQ is prioritized over input range flexibility. |
| LM5164QPWPRQ1 | 100 V input, 1 A, adjustable fSW (100 kHz–2.2 MHz), integrated compensation, no PG flag | Missing power good output limits use in systems requiring regulated-rail validation; different compensation architecture. | Choose when simplified design with internal compensation is preferred and PG flag is not required for system sequencing. |
Compared with LTC3639EMSE#PBF and LM5164QPWPRQ1, the LT8631HFE#PBF uniquely combines 100 V input capability, ±7.5% PG flag, and programmable Burst Mode/sync operation - making it the only option qualified for automotive under-hood and industrial high-temperature deployments requiring both reliability and precision monitoring.
Availability
LT8631HFE#PBF is available at Aetrix Electronics and suitable for automotive infotainment, industrial PLC I/O modules, and telecom remote radio units requiring stable component supply across extended temperature and high-reliability requirements.
Supply support for LT8631HFE#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 is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT8631HFE#PBF belongs to Analog Devices' monolithic synchronous buck regulator product line, designed specifically for ultrawide-input, high-temperature, and low-quiescent-current power conversion in harsh environments.
FAQ
What is the maximum junction temperature specification for the LT8631HFE#PBF?
The LT8631HFE#PBF is guaranteed over the full –40°C to +150°C junction temperature range, with thermal protection activating above 150°C. This H-grade qualification distinguishes it from E- and I-grade variants (both rated to 125°C) and enables deployment in under-hood automotive and high-ambient industrial applications where passive cooling is insufficient.
How does the LT8631HFE#PBF achieve 16 µA quiescent current in Burst Mode?
The LT8631HFE#PBF achieves 16 µA quiescent current by entering low-ripple Burst Mode below ~100 mA load: internal control circuitry shuts down between bursts, leaving only essential bias currents active. The 4.5 µA TR/SS current source remains enabled, but all switching, error amplifier, and oscillator functions are gated - verified at 12 VIN→5 VOUT with no load per datasheet Figure G03.
Can the LT8631HFE#PBF be synchronized to an external clock, and what are the requirements?
Yes, the LT8631HFE#PBF supports external synchronization via the SYNC/MODE pin. The external clock must be 100–1000 kHz, have 20–80% duty cycle, and be applied directly to SYNC/MODE. When detected, the LT8631HFE#PBF enters pulse-skipping mode and locks its switching edge to the rising edge of the external signal - enabling EMI reduction and deterministic timing in multi-rail systems.
What is the purpose of the exposed pad (Pin 21) on the LT8631HFE#PBF, and how must it be handled on the PCB?
The exposed pad (Pin 21) on the LT8631HFE#PBF is the sole GND connection and primary thermal path. It must be soldered to a large, low-thermal-resistance copper pour on the PCB - not left floating or connected only through traces. Per datasheet, this pad reduces θJA to 40°C/W and is mandatory for achieving full 1 A output at +150°C junction temperature; failure to solder it compromises both thermal performance and high-voltage creepage spacing.
Does the LT8631HFE#PBF support output voltage tracking, and how is it implemented?
Yes, the LT8631HFE#PBF supports output voltage tracking via the TR/SS pin. A shared capacitor between TR/SS and GND enables soft-start ramp coordination with other regulators; alternatively, an external voltage ramp applied to TR/SS forces the LT8631HFE#PBF's output to follow that ramp. This is used for controlled power-up sequencing in multi-rail systems such as FPGAs and SoCs where core and I/O voltages must ramp in defined order.
LT8631HFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-TSSOP (0.173", 4.40mm Width), 16 Leads, 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):
- 100V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 60V
- Current - Output:
- 1A
- Frequency - Switching:
- 100kHz ~ 1MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-TSSOP-EP
LT8631HFE#PBF FAQ
1.How can I place an order for LT8631HFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8631HFE#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 LT8631HFE#PBF reliable?
The price and inventory of LT8631HFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8631HFE#PBF is usually 5 days.
3.What payment methods are accepted for LT8631HFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8631HFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8631HFE#PBF?
LT8631HFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8631HFE#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 LT8631HFE#PBF?
For technical support, including LT8631HFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8631HFE#PBF requirements.
6.How does Aetrix verify that LT8631HFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT8631HFE#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 LT8631HFE#PBF meets industry standards.
7.What is the process for return or replacement of LT8631HFE#PBF?
All LT8631HFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8631HFE#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 LT8631HFE#PBF part is unused and in its original packaging.
Return procedure for LT8631HFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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