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Analog Devices Inc. LT1573IS8#PBF
- Part No.:
- LT1573IS8#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1573IS8#PBF.pdf
- Description:
- IC LNR REG CTRLR 1OUT 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:171
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Product details
Overview
LT1573IS8#PBF from Analog Devices (formerly Linear Technology) is a PNP regulator driver IC designed to control external PNP pass transistors in high-current, low-dropout linear regulator applications. It delivers precision 3.3V output (±1% over temperature), supports input voltages from 2.8V to 10V, achieves <0.35V dropout with D45H11, and integrates latching overcurrent protection without external sense resistors - enabling compact 5A microprocessor power supplies.
For engineers reviewing the LT1573IS8#PBF datasheet, LT1573IS8#PBF pinout, LT1573IS8#PBF application, or LT1573IS8#PBF equivalent, this page provides verified functional role, validated thermal and transient response specs, confirmed SO-8 package mapping, exact pin functions per block diagram, and two field-validated alternative drivers for 2.5–3.3V high-current LDO systems.
Technical Context
The LT1573IS8#PBF implements a fast-response error amplifier with a 1.265V internal reference, driving a Darlington output stage to sink up to 250mA base current into external PNP transistors. Its feedback loop uses VFB as inverting input referenced to 1.265V, enabling precise output regulation via resistor divider (adjustable) or internal divider (fixed 3.3V version).
Latching overcurrent protection operates via DRIVE pin saturation detection: when VDRIVE falls below 0.12–1.4V (depending on load), a timing capacitor on LATCH pin charges at ~7µA; latch triggers at ~2VBE (~1.2V). Shutdown (SHDN) resets latch or disables drive independently, with threshold at 1.0–1.6V and no VIN dependency.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±1% over –40°C to 125°C; enables direct replacement of 3.3V logic supply rails without trimming. |
| Input Voltage Range | 2.8V to 10V; supports post-regulation after 5V switching supplies or direct battery input down to LiFePO₄ minimum. |
| Drive Current Capability | 250mA max sink at DRIVE pin; sufficient to fully saturate D45H11/KSE45H11 at 5A output with <0.35V dropout. |
| Dropout Voltage (System) | As low as 0.35V at 5A with D45H11; determined by VCE(sat) of external PNP under 250mA base drive. |
| Line Regulation | 0.34mV typical over 3.5–7V input; ensures stable 3.3V output despite input ripple from upstream DC/DC converters. |
| Load Regulation | 18mV typical from 20mA to 250mA drive current; maintains tight regulation across full 5A output range via PNP β scaling. |
| Shutdown Threshold | 1.0–1.6V on SHDN pin; allows clean disable using standard logic-level signals or open-drain microcontroller GPIO. |
| Junction Temperature Range | –40°C to 125°C; qualified for industrial and extended-temperature embedded systems with active thermal management. |
Pinout & Package
LT1573IS8#PBF is housed in an 8-lead plastic SO (Small Outline) package with fused leads for enhanced thermal performance and reduced footprint. The package supports surface-mount assembly and provides θJA = 85°C/W in still air on standard FR-4 PCBs.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB (Pin 1) | Inverting input of error amplifier | Connected to voltage divider output; forces VFB = 1.265V for precise 3.3V regulation (internal divider). |
| LATCH (Pin 2) | Overcurrent timing node | External capacitor sets latch timeout; charges at ~7µA; latches off if fault persists beyond CEXT charge time. |
| SHDN (Pin 3) | Shutdown/reset control | Pull >1.3V to disable output or reset latch; sinks ≤200µA; compatible with 3.3V/5V logic. |
| GND (Pin 4) | Analog and power ground reference | Common return for internal bias, error amp, and protection circuitry; must be low-impedance connection. |
| DRIVE (Pin 5) | Base drive output | Sinks up to 250mA to drive PNP base; saturation voltage 0.12–1.4V defines overcurrent trigger point. |
| VIN (Pin 6) | Main power supply input | Provides bias for all internal circuits; rated to 10V absolute max; powers error amp, reference, and protection blocks. |
| VOUT (Pin 7) | Output voltage sensing node | Connects to regulator output; used by comparator C1 to disable latch during startup saturation. |
| COMP (Pin 8) | Compensation network connection | Accepts RC network (e.g., 1kΩ + 100pF) between VOUT and COMP to stabilize loop and optimize transient response. |
Key Features
| Feature | Design Value |
|---|---|
| Time-delayed latching overcurrent protection | Eliminates need for external current-sense resistor; reduces BOM count and PCB area while preventing thermal runaway during shorts. |
| Fast transient response architecture | Enables use of only 24×1µF ceramic + 220µF tantalum output capacitance for 5A microprocessor loads, cutting bulk cap volume by >60% vs conventional LDOs. |
| Single-supply operation from 2.8V | Supports direct integration with low-voltage battery sources (e.g., single-cell LiFePO₄) without auxiliary bias rails. |
| Thermal shutdown with no timing delay | Instantly disables output if junction exceeds 125°C, protecting both LT1573IS8#PBF and external PNP transistor under sustained overload. |
| Adjustable or fixed-output variants | This LT1573IS8#PBF is factory-configured for 3.3V fixed output; eliminates external feedback resistors and improves production yield consistency. |
Applications
| Microprocessor Core Supply | Post-Regulator for DC/DC Converters |
|---|---|
Use Scenario: Delivering clean, low-noise 3.3V power to ARM Cortex-A/M series SoCs with dynamic current draw from 0.2A to 5A. IC Role / Device Role / Timing Role: Regulator driver controlling external D45H11 PNP transistor; provides fast transient response and precise 3.3V regulation independent of upstream converter ripple. Use Value: Reduces required output capacitance by 60% versus standard LDOs, enabling placement directly in CPU socket cavity for lowest possible impedance path. | Use Scenario: Tightening output voltage tolerance of a 5V buck converter feeding FPGA I/O banks requiring ±1% 3.3V. IC Role / Device Role / Timing Role: Precision post-regulator driver; rejects switching noise via high PSRR error amplifier and fast loop compensation. Use Value: Achieves <18mV load regulation and <0.34mV line regulation - meeting FPGA VCCIO spec margins even under 2A step loads. |
| Industrial PLC Power Module | Automotive Body Control Unit (BCU) |
Use Scenario: Generating 3.3V for microcontrollers and CAN transceivers in DIN-rail mounted programmable logic controllers operating at –40°C to 85°C ambient. IC Role / Device Role / Timing Role: High-reliability linear regulator driver with latching fault protection; operates across full industrial temperature range with guaranteed 1% output accuracy. Use Value: Eliminates need for external current-sense components and simplifies thermal design - reducing failure modes in long-life, maintenance-free deployments. | Use Scenario: Providing fault-tolerant 3.3V supply for automotive body electronics exposed to load dump and cold crank conditions. IC Role / Device Role / Timing Role: Robust regulator driver with shutdown/reset capability and thermal shutdown; withstands 10V input transients and operates down to 2.8V during cranking. Use Value: Latch-off protection prevents thermal damage during sustained short circuits in wiring harnesses - critical for ASIL-B compliant systems. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar PNP regulator driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1573CS8-3.3#PBF | Commercial temperature grade (0°C to 125°C); same electrical specs, lower cost, not rated for –40°C start-up. | Preferred for consumer or lab equipment where ambient stays above 0°C; unsuitable for outdoor or automotive environments. | Select LT1573IS8#PBF when operation below –40°C is required; otherwise LT1573CS8-3.3#PBF offers cost advantage. |
| LT1581CS8#PBF | Higher drive current (500mA), wider input range (2.7V–20V), but no integrated latch-off; requires external current sense and timing circuitry. | Used where >5A output or higher input voltage is needed, but adds design complexity and component count for protection. | Choose LT1573IS8#PBF for drop-in 5A/3.3V industrial designs with integrated protection; LT1581CS8#PBF only if drive current or VIN headroom exceeds LT1573 limits. |
Compared with LT1573CS8-3.3#PBF, LT1573IS8#PBF guarantees full-spec operation at –40°C, making it essential for harsh-environment deployment; versus LT1581CS8#PBF, it trades raw drive capability for integrated, resistorless overcurrent protection - reducing design risk and bill-of-materials in 3.3V/5A applications.
Availability
LT1573IS8#PBF is available at Aetrix Electronics and suitable for microprocessor core supplies, industrial PLC power modules, and automotive body control units requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT1573IS8#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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors.
The LT1573 product line was developed specifically for high-current, ultra-low-dropout linear regulation using external PNP transistors - targeting applications demanding precision, speed, and robust fault protection without complex external circuitry.
FAQ
What is the exact output voltage tolerance of the LT1573IS8#PBF over its full operating temperature range?
The LT1573IS8#PBF delivers a fixed 3.3V output with ±1% tolerance over the full –40°C to 125°C junction temperature range. At 25°C, the typical output is 3.300V, with min/max values of 3.234V and 3.366V under specified load and input conditions - meeting strict microprocessor core voltage requirements without external trimming.
Can the LT1573IS8#PBF be used with NPN pass transistors instead of PNP?
No, the LT1573IS8#PBF is specifically designed as a PNP regulator driver and cannot drive NPN transistors. Its DRIVE pin sinks current to control the base of a PNP transistor; NPN configurations require sourcing drive current, which the LT1573IS8#PBF does not support. Using an NPN would invert control logic and violate internal biasing, resulting in malfunction or damage.
How does the latching overcurrent protection in the LT1573IS8#PBF reset after triggering?
The LT1573IS8#PBF latching overcurrent protection can be reset in three ways: (1) pulling the SHDN pin above 1.3V, (2) grounding the LATCH pin, or (3) cycling power to VIN. The latch remains active until one of these actions occurs - ensuring persistent fault isolation. Internal latching current (0.3–9.5mA depending on VIN and temperature) sustains the state without external components.
What external components are mandatory for basic operation of the LT1573IS8#PBF?
Four external components are mandatory for LT1573IS8#PBF operation: (1) an external PNP pass transistor (e.g., D45H11), (2) resistor RD between DRIVE and PNP base to limit drive current and enable latch-off, (3) resistor RB (typically 50Ω) from PNP emitter to GND to accelerate turn-off, and (4) a timing capacitor from LATCH to GND to set overcurrent timeout duration. No external feedback resistors are needed for the fixed 3.3V LT1573IS8#PBF.
Is the LT1573IS8#PBF RoHS-compliant and lead-free?
Yes, the LT1573IS8#PBF is RoHS-compliant and lead-free. The "#PBF" suffix explicitly denotes lead-free packaging per JEDEC J-STD-609, with matte tin lead finish and halogen-free molding compound. It meets EU RoHS Directive 2011/65/EU and is suitable for environmentally regulated industrial and automotive applications.
LT1573IS8#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- Positive Adjustable
- Number of Outputs:
- 1
- Current - Supply:
- 1.7mA
- Voltage - Input:
- 2.8V ~ 10V
- Operating Temperature:
- -40°C ~ 125°C
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LT1573IS8#PBF FAQ
1.How can I place an order for LT1573IS8#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1573IS8#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 LT1573IS8#PBF reliable?
The price and inventory of LT1573IS8#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1573IS8#PBF is usually 5 days.
3.What payment methods are accepted for LT1573IS8#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1573IS8#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1573IS8#PBF?
LT1573IS8#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1573IS8#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 LT1573IS8#PBF?
For technical support, including LT1573IS8#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1573IS8#PBF requirements.
6.How does Aetrix verify that LT1573IS8#PBF is sourced from the original manufacturer or authorized distributors?
All LT1573IS8#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 LT1573IS8#PBF meets industry standards.
7.What is the process for return or replacement of LT1573IS8#PBF?
All LT1573IS8#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1573IS8#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 LT1573IS8#PBF part is unused and in its original packaging.
Return procedure for LT1573IS8#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT1573IS8#PBF Tags
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