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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Voltage Regulators - Linear Regulator Controllers

Analog Devices Inc. LT1575CN8-3.5

Name: LT1575CN8-3.5
Brand: Analog Devices Inc.
SKU: LT1575CN8-3.5
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LT1575CN8-3.5

Manufacturer:: Analog Devices Inc.

Category:: Voltage Regulators - Linear Regulator Controllers

Package:: 8-DIP (0.300", 7.62mm)

Datasheet:: LT1575CN8-3.5.pdf

Description:: IC LNR REG CTRLR 1OUT 8DIP

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Product details

Overview

LT1575CN8-3.5 from Analog Devices (formerly Linear Technology) is a fixed-output 3.5V, ultrafast transient response low-dropout regulator controller IC that drives external N-channel MOSFETs in source-follower configuration. It delivers ±1% output voltage accuracy over temperature, supports up to 5A load current, achieves <500ns transient response, and eliminates bulk electrolytic/tantalum output capacitors - used in Pentium® and PowerPC™ microprocessor core supplies.

For engineers reviewing the LT1575CN8-3.5 datasheet, LT1575CN8-3.5 pinout, LT1575CN8-3.5 application, or LT1575CN8-3.5 equivalent, key selection criteria include its 3.5V fixed output, PDIP-8 package, 1.21V internal reference, high-side current limit with 50mV threshold, and multifunction SHDN pin supporting latchoff, overvoltage, and thermal protection.

Technical Context

The LT1575CN8-3.5 implements a precision error amplifier with 15 mS transconductance and 84 dB open-loop gain, driving an integrated gate buffer capable of sourcing/sinking 50 mA peak for fast MOSFET gate slewing. Its feedback loop uses the OUT pin (not FB), internally tied to a trimmed resistor divider referencing the 1.21 V bandgap.

Protection architecture includes a high-side current sense amplifier (50 mV threshold), a programmable SHDN timer activated by current limit, and comparator-based overvoltage/thermal shutdown via resistor-divider biasing of the SHDN pin - all operating without external op-amps or discrete logic.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	Fixed 3.5 V ±0.6% at 25°C; ±1% over 0°C to 70°C ambient - enables direct core supply for 3.3–3.6 V logic families without trimming.
Reference Voltage	1.21 V ±0.6% - precision-trimmed bandgap used internally to set output via fixed resistor divider.
Load Regulation	Typical 1 mV - ensures stable output under dynamic CPU load steps from 0.2 A to 5 A.
Current Limit Threshold	50 mV ±8% - defines trip point across IPOS range (3–20 V); sets max output current via external sense resistor.
Supply Current (IQ)	5–19 mA - scales with VIN (8–20 V); enables low-quiescent design for always-on power rails.
Operating Temperature	0°C to 70°C ambient - validated for commercial motherboard environments; junction limited to 100°C.
GATE Output Swing	VIN − 1.6 V (high), 2.5–3.0 V (low) - provides sufficient gate drive headroom for N-MOSFETs with VGS(th) > 3 V − VOUT.

Pinout & Package

LT1575CN8-3.5 is housed in an 8-lead PDIP (Plastic Dual In-line Package) with 0.3-inch body width and through-hole mounting. Thermal resistance θJA = 100°C/W. Pin 1 is SHDN; pin 3 is GND (analog ground and reference return); pin 4 is OUT (feedback node for fixed-output versions).

Pin/Terminal	Circuit Role	Design Meaning
SHDN (1)	Multifunction shutdown input	Accepts resistor-divider bias for overvoltage/thermal protection; activates latchoff timer on current limit; reset by pulling below 1.21 V.
VIN (2)	Main IC supply input	Powers internal circuitry and gate driver; operates 3–22 V; must exceed VOUT + VGS(th) + 1.6 V for full gate swing.
GND (3)	Analog ground / reference return	Return path for 1.21 V reference and feedback network; must be star-connected to minimize noise coupling.
OUT (4)	Fixed-output feedback node	Internally connected to precision resistor divider; ties directly to regulated output for optimal regulation accuracy.
COMP (5)	Error amplifier high-impedance gain node	External RC compensation point; transconductance = 15 mS; open-loop gain ≈ 84 dB.
GATE (6)	MOSFET gate driver output	Sources/sinks 50 mA peak; drives ≤5000 pF gate capacitance; output impedance ≈ 2 Ω.
INEG (7)	Negative current sense input	High-side current limit amplifier inverting input; tie to IPOS to disable current limit.
IPOS (8)	Positive current sense input	Connects to main input rail; also enables startup monitoring of MOSFET VDS to prevent premature SHDN activation.

Key Features

Feature	Design Value
Ultrafast transient response	Eliminates need for bulk electrolytic/tantalum output capacitors - only 24 × 1 µF ceramic caps required for Pentium® processors.
FET R_DS(ON)-defined dropout	Dropout voltage set solely by external MOSFET's on-resistance - enables sub-100 mV dropout with appropriate FET selection.
1% reference/output tolerance over temp	Ensures ±35 mV absolute output deviation across 0°C–70°C - critical for tight-tolerance microprocessor core rails.
High-side sense current limit	50 mV threshold enables accurate, noise-immune current limiting without affecting main feedback loop stability.
Multifunction SHDN with latchoff	Single pin supports programmable time-out shutdown, overvoltage protection, and thermal shutdown - reduces BOM count and PCB area.

Applications

Pentium® Processor Core Supply	PowerPC™ I/O Supply
Use Scenario: Regulating 12 V input to stable 3.5 V for Intel Pentium® processor core during rapid 0.2 A → 5 A load transients. IC Role / Device Role / Timing Role: Controller IC driving IRFZ24 N-MOSFET as source follower; provides feedback via OUT pin and compensates loop at COMP pin. Use Value: Achieves sub-500 ns transient recovery with only 24 × 1 µF ceramic capacitors - removes 200+ µF bulk electrolytics and saves >$0.35 per board in capacitor cost.	Use Scenario: Generating clean 3.5 V rail for PowerPC™ I/O buffers requiring low-noise, fast-response regulation near FPGA or ASIC interfaces. IC Role / Device Role / Timing Role: Fixed-output LDO controller with high PSRR and <1 mV load regulation - rejects switching noise from adjacent DC/DC converters. Use Value: Maintains ±100 mV output window during 100 ns load steps - meets JEDEC JESD8-12B I/O supply spec without additional filtering.
GTL Bus Termination	Low-Voltage Logic (LVTTL/LVCMOS) Supply
Use Scenario: Providing precisely regulated 3.5 V termination voltage for GTL (Gunning Transceiver Logic) buses in high-speed backplanes. IC Role / Device Role / Timing Role: Fixed-output controller with 1% accuracy and 1 mV load regulation - maintains GTL reference stability across temperature and load. Use Value: Enables reliable 100+ MHz GTL signaling by holding termination voltage within ±15 mV of nominal - prevents signal integrity degradation.	Use Scenario: Powering 3.3–3.6 V logic families (e.g., LVTTL, LVCMOS) in industrial controllers where input ripple and load step rejection are critical. IC Role / Device Role / Timing Role: Low-dropout controller with VIN down to 3 V + VGS(th) + 1.6 V - supports wide-input industrial 5–15 V rails. Use Value: Delivers 5 A continuous current with <100 mV dropout using IRFZ24 - extends operational range beyond standard 3-terminal regulators.

Pentium® Processor Core Supply

PowerPC™ I/O Supply

Use Scenario: Regulating 12 V input to stable 3.5 V for Intel Pentium® processor core during rapid 0.2 A → 5 A load transients.

IC Role / Device Role / Timing Role: Controller IC driving IRFZ24 N-MOSFET as source follower; provides feedback via OUT pin and compensates loop at COMP pin.

Use Value: Achieves sub-500 ns transient recovery with only 24 × 1 µF ceramic capacitors - removes 200+ µF bulk electrolytics and saves >$0.35 per board in capacitor cost.

Use Scenario: Generating clean 3.5 V rail for PowerPC™ I/O buffers requiring low-noise, fast-response regulation near FPGA or ASIC interfaces.

IC Role / Device Role / Timing Role: Fixed-output LDO controller with high PSRR and <1 mV load regulation - rejects switching noise from adjacent DC/DC converters.

Use Value: Maintains ±100 mV output window during 100 ns load steps - meets JEDEC JESD8-12B I/O supply spec without additional filtering.

GTL Bus Termination

Low-Voltage Logic (LVTTL/LVCMOS) Supply

Use Scenario: Providing precisely regulated 3.5 V termination voltage for GTL (Gunning Transceiver Logic) buses in high-speed backplanes.

IC Role / Device Role / Timing Role: Fixed-output controller with 1% accuracy and 1 mV load regulation - maintains GTL reference stability across temperature and load.

Use Value: Enables reliable 100+ MHz GTL signaling by holding termination voltage within ±15 mV of nominal - prevents signal integrity degradation.

Use Scenario: Powering 3.3–3.6 V logic families (e.g., LVTTL, LVCMOS) in industrial controllers where input ripple and load step rejection are critical.

IC Role / Device Role / Timing Role: Low-dropout controller with VIN down to 3 V + VGS(th) + 1.6 V - supports wide-input industrial 5–15 V rails.

Use Value: Delivers 5 A continuous current with <100 mV dropout using IRFZ24 - extends operational range beyond standard 3-terminal regulators.

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-dropout regulator controller applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
LT1575CS8-3.5	Same electrical specs; SO-8 package (θJA = 130°C/W vs PDIP's 100°C/W); surface-mount only.	Preferred for automated assembly and space-constrained boards; requires reflow profile validation.	Select LT1575CS8-3.5 when PCB layout mandates SMT or thermal budget allows higher θJA.
LT1577CS-3.3/ADJ	Dual-output controller (3.3 V fixed + adjustable); 16-pin SO; independent current limit per channel; no 3.5 V option.	Used in dual-rail systems (e.g., core + I/O); cannot replace single 3.5 V rail without redesign.	Choose LT1577CS-3.3/ADJ only when dual outputs and flexibility outweigh cost/size penalties of extra channel.

Compared with LT1575CS8-3.5, the LT1575CN8-3.5 offers lower thermal resistance for through-hole prototyping and manual rework; compared with LT1577CS-3.3/ADJ, it provides lower cost, smaller footprint, and simpler layout for single-rail 3.5 V applications - making it optimal for cost-sensitive, high-volume motherboard designs.

Availability

LT1575CN8-3.5 is available at Aetrix Electronics and suitable for Pentium® processor core supplies, PowerPC™ I/O rails, GTL bus termination, and low-voltage logic power distribution requiring stable component supply and long-term obsolescence management.

Supply support for LT1575CN8-3.5 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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and computing markets.

The LT1575 series belongs to Linear Technology's UltraFast™ transient response regulator controller product line, designed specifically to replace bulky capacitor networks in high-speed microprocessor power supplies while maintaining precision, reliability, and ease of use.

FAQ

What is the output voltage tolerance of the LT1575CN8-3.5 over temperature?

The LT1575CN8-3.5 guarantees ±1% output voltage tolerance across the full operating ambient temperature range of 0°C to 70°C. At 25°C, tolerance tightens to ±0.6%. This is achieved via factory-trimmed internal resistor divider referenced to a ±0.6% 1.21 V bandgap - ensuring compliance with tight-core-voltage requirements for Pentium® and PowerPC™ processors. The LT1575CN8-3.5 maintains this accuracy without external calibration.

Can the LT1575CN8-3.5 be used without an external current sense resistor?

Yes - the LT1575CN8-3.5 supports "sense-less" current limiting by grounding the INEG pin. This disables the high-side current sense amplifier and activates an internal saturation detector on the GATE pin. When GATE swings to VIN (indicating MOSFET saturation), the SHDN timer triggers latchoff. This mode avoids 50 mV sense loss but trades off current accuracy for short-circuit robustness. The LT1575CN8-3.5 remains fully functional in either configuration.

What package type does the LT1575CN8-3.5 use, and what are its thermal characteristics?

The LT1575CN8-3.5 uses an 8-lead PDIP (plastic dual in-line package) with 0.3-inch body width and through-hole leads. Its junction-to-ambient thermal resistance is θJA = 100°C/W. Maximum junction temperature is 100°C, limiting continuous power dissipation to ~700 mW at 70°C ambient. This makes the LT1575CN8-3.5 suitable for moderate-power, manually assembled, or prototyped motherboard rails where thermal mass aids heat spreading.

How does the SHDN pin function in overvoltage protection mode for the LT1575CN8-3.5?

The SHDN pin serves as the positive input to an internal comparator referenced to the 1.21 V bandgap. Applying a resistor divider from VIN to GND to SHDN sets a precise overvoltage trip point: when SHDN voltage exceeds 1.21 V + 100 mV (typical hysteresis), the comparator latches GATE low. For example, a 10 kΩ/2.2 kΩ divider from 12 V trips at ~6.6 V output. This protection is active independently of current limit and resets only when SHDN falls below 1.11 V - ensuring robust fault handling in the LT1575CN8-3.5.

Which external MOSFET parameters are critical for stable operation of the LT1575CN8-3.5?

Three MOSFET parameters are critical for the LT1575CN8-3.5: (1) VGS(th) > 3 V − VOUT (i.e., > −0.5 V for 3.5 V output - satisfied by all logic-level N-MOSFETs), (2) gate capacitance ≤ 5000 pF to avoid loop instability, and (3) RDS(ON) selected to meet dropout target (e.g., 20 mΩ yields ~100 mV dropout at 5 A). The LT1575CN8-3.5 has been validated with IRFZ24; gate resistors of 2–10 Ω are recommended for MOSFETs with <1500 pF input capacitance to damp LC ringing.

LT1575CN8-3.5 Specifications

Product attributes: Attribute value

Manufacturer:: Analog Devices Inc.

Series:: -

Package/Case:: 8-DIP (0.300", 7.62mm)

Packaging:: Tube

Product Status:: Active

Type:: Positive Fixed

Number of Outputs:: 1

Current - Supply:: 12mA

Voltage - Input:: 10V ~ 20V

Operating Temperature:: 0°C ~ 70°C

Mounting Type:: Through Hole

Supplier Device Package:: 8-PDIP

LT1575CN8-3.5 FAQ

1.How can I place an order for LT1575CN8-3.5 through Aetrix?

Please submit a Request for Quotation (RFQ) for LT1575CN8-3.5 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 LT1575CN8-3.5 reliable?

The price and inventory of LT1575CN8-3.5 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1575CN8-3.5 is usually 5 days.

3.What payment methods are accepted for LT1575CN8-3.5?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1575CN8-3.5 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LT1575CN8-3.5?

LT1575CN8-3.5 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LT1575CN8-3.5 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 LT1575CN8-3.5?

For technical support, including LT1575CN8-3.5 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1575CN8-3.5 requirements.

6.How does Aetrix verify that LT1575CN8-3.5 is sourced from the original manufacturer or authorized distributors?

All LT1575CN8-3.5 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 LT1575CN8-3.5 meets industry standards.

7.What is the process for return or replacement of LT1575CN8-3.5?

All LT1575CN8-3.5 units undergo pre-shipment inspection (PSI). If there is an issue with LT1575CN8-3.5, 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 LT1575CN8-3.5 part is unused and in its original packaging.

Return procedure for LT1575CN8-3.5:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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