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Analog Devices Inc. LTC1538IG-AUX#PBF
- Part No.:
- LTC1538IG-AUX#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 28-SSOP (0.209", 5.30mm Width)
- Datasheet:
-
LTC1538IG-AUX#PBF.pdf
- Description:
- IC REG CTRLR BUCK 28SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,594
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Product details
Overview
LTC1538IG-AUX#PBF from Analog Devices (formerly Linear Technology) is a dual synchronous step-down switching regulator controller driving external N-channel MOSFETs in a phase-lockable fixed-frequency architecture. It delivers two independent regulated outputs - one fixed 3.3V/5V (Controller 1), one adjustable 1.19V–9V (Controller 2) - with up to 3.5A per channel, 99% duty cycle dropout operation, and integrated 5V/20mA standby regulator. It is used in notebook computers and portable instrumentation requiring high efficiency across wide input range (3.5V–36V).
For engineers reviewing the LTC1538IG-AUX#PBF datasheet, LTC1538IG-AUX#PBF pinout, LTC1538IG-AUX#PBF application, or LTC1538IG-AUX#PBF equivalent, key selection criteria include dual-channel programmable output voltage, adaptive power mode for low-load efficiency, remote sensing on Channel 2, integrated POR timer, and SSOP-28 package compatibility with thermal derating at –40°C to +85°C.
Technical Context
The LTC1538IG-AUX#PBF implements constant-frequency current-mode control with dual independent error amplifiers, each feeding ITH pins that set peak inductor current via external sense resistors. Its Adaptive Power™ architecture dynamically switches between large (TGL/BG) and small (TGS) top-side MOSFET drivers to maintain fixed-frequency operation down to ~1% load - avoiding burst-mode noise while minimizing gate charge losses.
It integrates a 5V/20mA INTVCC LDO active during full shutdown, an auxiliary linear regulator controlled via AUXON/AUXDR/AUXFB for 12V or adjustable VPP generation, and a secondary feedback input (SFB1) forcing continuous conduction on Controller 1 - critical for flyback-derived auxiliary supplies. The device lacks PLLIN and PLL LPF pins, distinguishing it from the LTC1539 variant.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.5V to 36V - supports wide industrial and battery-powered inputs including 12V/24V rails and Li-ion stacks. |
| Output Voltage Options | Channel 1: 3.3V or 5.0V only (VPROG1-selectable); Channel 2: 1.19V to 9V adjustable via VOSENSE2 and external divider. |
| Max Output Current | 3.5A per channel - determined by external MOSFETs and RSENSE (e.g., 0.03Ω yields ~150mV threshold). |
| Operating Frequency | 112–138kHz (typ 125kHz) - set by COSC capacitor; no PLL capability (pins absent in LTC1538-AUX). |
| Shutdown Quiescent Current | <200µA - enables ultra-low-power standby with 5V regulator and reference active. |
| Temperature Range | –40°C to +85°C (Industrial grade) - validated for extended ambient operation with θJA = 95°C/W (SSOP-28). |
| Dropout Capability | 99% duty cycle - maintains regulation under near-zero VIN–VOUT differential, critical for low-voltage systems. |
Pinout & Package
Package: 28-lead plastic SSOP (G package), 0.635mm pitch, exposed pad not electrically connected. Thermal resistance θJA = 95°C/W; suitable for standard reflow and manual soldering with controlled moisture sensitivity level (MSL 3).
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| BOOST 1 / BOOST 2 | Floating top-side gate driver supply | Provides bias for TGL1/TGL2 drivers; requires bootstrap capacitors tied to SW1/SW2 nodes. |
| TGL1 / TGL2 | High-current top-side N-MOSFET gate drive | Drives large external N-channel MOSFETs (e.g., Si4412DY); swing = INTVCC superimposed on SW node. |
| BG1 / BG2 | Bottom-side N-MOSFET gate drive | Sinks/source current to turn on/off synchronous rectifiers; swing = 0V to INTVCC. |
| SENSE+ 1 / SENSE+ 2 | Current sense comparator non-inverting input | Paired with SENSE– to detect RSENSE voltage drop; built-in offset sets trip threshold (~150mV). |
| VOSENSE2 | Remote feedback input (Channel 2 only) | Enables true remote sensing for Channel 2 output; required for precision regulation under PCB trace IR drop. |
| RUN/SS1 / RUN/SS2 | Combined enable & soft-start control | Pulling below 1.3V disables respective channel; capacitor to ground sets ramp time (~0.5s/µF). |
| INTVCC/5V | Internal 5V LDO output | Supplies internal logic and gate drivers; remains active in shutdown; requires ≥2.2µF local capacitance. |
| PGND | Power ground return | Connects to sources of bottom MOSFETs and (–) terminals of input capacitors - separate from SGND. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent controllers | Enables simultaneous 5V/3.3V or 5V/adjustable rails from single IC - reduces BOM count and layout area. |
| Adaptive Power™ mode | Maintains fixed-frequency operation down to ~1% load by switching between TGL (high-current) and TGS (low-current) drivers - eliminates burst-mode EMI. |
| Integrated 5V/20mA standby regulator | Remains powered during full shutdown - supports real-time clocks, memory retention, and wake-up circuitry without external LDO. |
| Programmable soft start & POR timer | Capacitor-controlled ramp (RUN/SS pins) prevents inrush; POR1 asserts after 65536 oscillator cycles (~300ms at 125kHz) once output reaches ±5% regulation. |
| Remote sensing on Channel 2 | VOSENSE2 pin allows Kelvin connection to load - compensates for PCB trace resistance and ensures accurate load regulation. |
| Low-battery detection | LBI/LBO pins provide dedicated comparator with 1.19V internal reference - enables system-level brownout protection independent of RUN/SS state. |
Applications
| Portable Instrumentation | Notebook Computing |
|---|---|
|
Use Scenario: Handheld multimeters and data loggers powered by 2–3-cell Li-ion batteries with dynamic load profiles. IC Role / Device Role: Dual-output DC/DC controller generating stable 3.3V for microcontroller and 5V for analog front-end, with adaptive efficiency scaling. Use Value: Extends battery runtime by >25% vs. fixed-frequency-only regulators at light loads, while maintaining low-noise 3.3V rail for precision ADCs. |
Use Scenario: Embedded subsystems in ultrabooks requiring isolated 5V standby and main 3.3V domain. IC Role / Device Role: Primary power controller managing both always-on 5V rail (via INTVCC) and switched 3.3V rail (via RUN/SS2), with POR sequencing. Use Value: Eliminates need for discrete 5V LDO and reset IC - reduces component count and improves cold-start reliability. |
| DC Power Distribution | Industrial Portable Equipment |
|
Use Scenario: DIN-rail mounted test equipment drawing from 24V DC bus with strict ripple and transient requirements. IC Role / Device Role: Dual-channel buck controller delivering 5V for digital logic and 3.3V for communication interfaces (RS-485, CAN transceivers). Use Value: Achieves <15mVpp output ripple at full load via synchronous rectification and remote sensing - meets EN 61000-4-4 immunity thresholds. |
Use Scenario: Ruggedized handheld HMI panels operating in –25°C to +70°C ambient with intermittent high-current backlight loads. IC Role / Device Role: Regulator controlling 5V display backlight driver and 3.3V MCU core, using SFB1 to force continuous mode during backlight dimming transitions. Use Value: Prevents audible coil whine during PWM dimming by eliminating burst-mode discontinuities - improves user experience. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC1539IGW#PBF | 36-pin SSOP package; includes PLLIN and PLL LPF pins for external frequency synchronization - absent in LTC1538IG-AUX#PBF. | Required where system-level clock alignment (e.g., to USB or PCIe reference) is mandatory; adds board space and passive components. | Select when deterministic switching frequency alignment is needed; otherwise LTC1538IG-AUX#PBF offers identical regulation performance in smaller footprint. |
| MP2451DT-LF-Z | Single-channel 2A buck controller (no dual output); no adaptive power mode; fixed 3.3V/5V options only; no remote sensing or SFB1. | Suitable only for simpler single-rail systems; lacks auxiliary regulator, POR, and low-battery detection functions. | Choose for cost-sensitive, space-constrained designs needing only one regulated output - not a functional replacement for dual-channel use cases. |
Compared with LTC1539IGW#PBF, LTC1538IG-AUX#PBF trades PLL synchronization capability for reduced pin count and smaller SSOP-28 package, while retaining identical control loop accuracy, efficiency, and feature set for standalone dual-rail applications. MP2451DT-LF-Z provides no path to replicate the dual-output, remote-sense, or auxiliary-regulator functionality of LTC1538IG-AUX#PBF.
Availability
LTC1538IG-AUX#PBF is available at Aetrix Electronics and suitable for notebook computing, portable instrumentation, and industrial portable equipment requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LTC1538IG-AUX#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 industrial, automotive, communications, and healthcare markets.
The LTC1538-AUX product line was designed specifically for dual-output, high-efficiency DC/DC conversion in space-constrained portable systems - emphasizing adaptive efficiency, robust protection features, and seamless integration with external power stages.
FAQ
What is the maximum supported input voltage for the LTC1538IG-AUX#PBF?
The LTC1538IG-AUX#PBF supports an absolute maximum input voltage of 36V on the VIN pin. Continuous operation is specified from 3.5V to 30V, making it suitable for 12V and 24V industrial rails as well as multi-cell Li-ion battery packs. Exceeding 36V risks permanent damage to internal circuitry and gate drivers.
Does the LTC1538IG-AUX#PBF support remote voltage sensing on both output channels?
No. Remote sensing is supported only on Channel 2 via the VOSENSE2 pin. Channel 1 (SENSE–1) is internally connected to its output node, preventing true remote sensing - it is limited to 3.3V or 5.0V fixed outputs selected by VPROG1. This architectural distinction is documented in the Pin Functions section of the datasheet.
Can the LTC1538IG-AUX#PBF operate in dropout mode, and what is its minimum dropout voltage?
Yes. The LTC1538IG-AUX#PBF supports ultralow dropout operation with up to 99% duty cycle, enabling regulation when VIN approaches VOUT. The effective dropout voltage is determined by RDS(on) of external high-side MOSFET and gate drive strength - typical practical dropout is <200mV at 1A with appropriate FET selection.
What is the function of the SFB1 pin on the LTC1538IG-AUX#PBF?
The SFB1 pin forces continuous conduction mode on Controller 1 when pulled below 1.19V. It is used primarily in flyback-derived auxiliary supplies to guarantee regulation regardless of main output loading. In non-flyback applications, SFB1 is tied to INTVCC or grounded depending on desired operational mode - a key differentiator from standard buck controllers.
Is the 5V standby regulator on the LTC1538IG-AUX#PBF active during full shutdown?
Yes. The INTVCC/5V regulator remains fully operational even when both RUN/SS1 and RUN/SS2 pins are held low, delivering up to 20mA at <200µA quiescent current. This enables always-on functions such as RTC backup, memory retention, and wake-up logic without requiring additional regulators - a defining feature of the LTC1538-AUX family.
LTC1538IG-AUX#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-SSOP (0.209", 5.30mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Number of Outputs:
- 2
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 3.5V ~ 30V
- Frequency - Switching:
- Up to 400kHz
- Duty Cycle (Max):
- 99%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Enable, Power on Reset, Soft Start
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-SSOP
LTC1538IG-AUX#PBF FAQ
1.How can I place an order for LTC1538IG-AUX#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1538IG-AUX#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 LTC1538IG-AUX#PBF reliable?
The price and inventory of LTC1538IG-AUX#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1538IG-AUX#PBF is usually 5 days.
3.What payment methods are accepted for LTC1538IG-AUX#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1538IG-AUX#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1538IG-AUX#PBF?
LTC1538IG-AUX#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1538IG-AUX#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 LTC1538IG-AUX#PBF?
For technical support, including LTC1538IG-AUX#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1538IG-AUX#PBF requirements.
6.How does Aetrix verify that LTC1538IG-AUX#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1538IG-AUX#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 LTC1538IG-AUX#PBF meets industry standards.
7.What is the process for return or replacement of LTC1538IG-AUX#PBF?
All LTC1538IG-AUX#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1538IG-AUX#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 LTC1538IG-AUX#PBF part is unused and in its original packaging.
Return procedure for LTC1538IG-AUX#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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