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Analog Devices Inc. LT3570IUF#TRPBF
- Part No.:
- LT3570IUF#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Voltage Regulators - Linear + Switching
- Package:
- 24-WFQFN Exposed Pad
- Datasheet:
-
LT3570IUF#TRPBF.pdf
- Description:
- IC REG TRIPLE BUCK/BST/LNR 24QFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,102
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Product details
Overview
LT3570IUF#TRPBF from Analog Devices (formerly Linear Technology) is a triple-output power management IC integrating a 1.5A buck converter, a 1.5A boost converter, and an LDO controller with external NPN transistor drive. It operates from 2.5V to 36V input, supports programmable switching frequency up to 2.1MHz, delivers regulated outputs down to 0.8V, and targets multi-rail industrial power systems requiring compact, high-efficiency DC/DC conversion.
For engineers reviewing the LT3570IUF#TRPBF datasheet, LT3570IUF#TRPBF pinout, LT3570IUF#TRPBF application, or LT3570IUF#TRPBF equivalent, key selection criteria include independent soft-start per channel, separate VIN supplies for buck/boost/LDO sections, 788mV feedback reference accuracy, thermal shutdown protection, and QFN-24 (4mm × 4mm) package compatibility with high-density PCB layouts.
Technical Context
The LT3570IUF#TRPBF implements constant-frequency current-mode control for both buck and boost regulators, each with dedicated error amplifiers (VC1/VC2), soft-start pins (SS1/SS2), and feedback inputs (FB1/FB2) referenced to 788mV. The LDO controller drives an external NPN transistor via NPN_DRV with up to 10mA base current and uses FB3 for output regulation.
It features independent shutdown pins (SHDN1/SHDN2/SHDN3) enabling selective activation of each regulator, SYNC capability for external clock synchronization up to 2.75MHz, and BIAS pin support for reduced quiescent current when powered from a low-voltage auxiliary rail.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.5V to 36V - supports wide-input industrial, automotive, and telecom rails without pre-regulation. |
| Buck/Boost Current Limit | 1.5A typical - defines maximum continuous inductor current per switching regulator, limiting peak switch stress. |
| Feedback Reference Voltage | 788mV ±16mV - sets output voltage accuracy via resistor divider; enables precise 3.3V, 5V, 12V, or custom rail generation. |
| Switching Frequency Range | 500kHz to 2.1MHz - adjustable via RT resistor; higher frequencies allow smaller magnetics and faster transient response. |
| Soft-Start Time Control | Programmable via capacitor on SS1/SS2 - limits inrush current and prevents output overshoot during power-up. |
| LDO Controller Output | Up to 10mA base drive - sufficient to bias medium-power external NPN transistors for linear post-regulation or "dying gasp" hold-up. |
| Operating Temperature | –40°C to +125°C - qualified for extended industrial and automotive under-hood environments. |
| Package | 24-Lead (4mm × 4mm) QFN with exposed pad - provides low thermal resistance (θJA = 37°C/W) and space-efficient layout. |
Pinout & Package
LT3570IUF#TRPBF is housed in a 24-lead plastic QFN package (4mm × 4mm) with exposed thermal pad (Pin 25) that must be soldered to PCB ground for electrical integrity and thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN2 (Pins 1,2) | Buck Regulator Input Supply | Primary power source for internal circuitry and buck switch; requires local 10μF ceramic bypass. |
| SW2 (Pin 3) | Buck Switch Node | Emitter of internal NPN switch; connects to inductor, catch diode, and BOOST capacitor. |
| SW1 (Pin 4) | Boost Switch Node | Collector of internal NPN switch; connects to boost inductor and Schottky diode. |
| GND (Pins 5,6,16,25) | Ground Reference | Common return for all regulators; exposed pad (Pin 25) is mandatory GND connection for thermal and EMI control. |
| VIN1 (Pin 7) | Boost Regulator Input | Supplies current only to boost section; isolated from buck/LDO domains for flexible rail assignment. |
| SS1 (Pin 8) | Boost Soft-Start | Charged by 4.5μA current to 2V; controls ramp rate of boost reference voltage during startup. |
| VC1 (Pin 9) | Boost Error Amplifier Compensation | Connect RC network to ground to stabilize boost loop; threshold ~750mV triggers current limit. |
| FB1 (Pin 10) | Boost Feedback Input | Regulated to 788mV; resistor divider from VOUT1 sets output voltage (e.g., 12V with 10.2k/22.1k). |
| SHDN1 (Pin 11) | Boost Enable Control | ≥1.4V enables boost; <0.3V disables - allows independent sequencing with other regulators. |
| SHDN2 (Pin 12) | Buck Enable Control | ≥1.4V enables buck; <0.3V disables - supports staggered power-up in multi-rail systems. |
| SHDN3 (Pin 13) | LDO Controller Enable | ≥1.5V enables NPN_DRV; <0.3V disables - isolates LDO function without affecting switching sections. |
| SYNC (Pin 14) | External Clock Input | Accepts TTL/CMOS clock up to 2.75MHz; synchronizes internal oscillator to reduce EMI peaks. |
| RT (Pin 15) | Frequency Set Resistor | Resistor to GND sets oscillator frequency (e.g., 44.2k → 500kHz; 7.87k → 2.1MHz). |
| SS2 (Pin 17) | Buck Soft-Start | Charged identically to SS1; independently controls buck reference ramp for clean startup. |
| VC2 (Pin 18) | Buck Error Amplifier Compensation | RC compensation node for buck loop; 700mV threshold initiates current limiting. |
| FB2 (Pin 19) | Buck Feedback Input | Regulated to 788mV; resistor divider from VOUT2 sets buck output (e.g., 3.3V with 22k/143k). |
| FB3 (Pin 20) | LDO Feedback Input | Regulated to 788mV; resistor divider from VOUT3 sets LDO-controlled output (e.g., 2.5V with 32.4k/10k). |
| NPN_DRV (Pin 21) | External NPN Base Drive | Delivers up to 10mA base current sourced from VIN3; enables discrete linear regulation or hold-up. |
| VIN3 (Pin 22) | LDO Controller Input | Supplies current only to NPN_DRV and FB3 circuitry; bypassed locally for stable LDO operation. |
| BIAS (Pin 23) | Auxiliary Bias Supply | Optional low-voltage supply (>2.5V) to reduce quiescent current; if unused, tied to VIN2. |
| BOOST (Pin 24) | Buck NPN Boost Bias | Charged above VIN2 via external Schottky diode; ensures saturation of internal NPN switch. |
Key Features
| Feature | Design Value |
|---|---|
| Triple independent regulators | Enables single-chip solution for 12V/3.3V/2.5V or other combinations without cross-coupling or shared thermal paths. |
| Separate VIN supplies per regulator | Allows optimized input sourcing - e.g., VIN1 from battery, VIN2 from main rail, VIN3 from auxiliary supply - improving system flexibility. |
| Programmable soft-start per channel | Prevents inrush into downstream capacitors and avoids bus droop during sequential power-up of multiple rails. |
| Synchronization up to 2.75MHz | Eliminates beat frequencies in multi-converter systems and simplifies EMI filter design by locking switching noise to known spectrum. |
| 788mV precision feedback reference | Ensures ±1% output voltage accuracy across temperature and line variations, critical for sensitive analog or digital loads. |
| Exposed-pad QFN thermal design | θJA = 37°C/W enables reliable 1.5A operation at full load without heatsink, supporting compact industrial modules. |
Applications
| Cable Set-Top Box Power | Automotive Infotainment System |
|---|---|
|
Use Scenario: Generating 12V for tuner modules, 3.3V for SoC core, and 2.5V for memory interface in space-constrained STB designs. IC Role / Device Role / Timing Role: Triple-output PMIC managing independent power domains with sequenced startup and fault isolation. Use Value: Reduces component count by replacing three discrete converters; maintains tight regulation under dynamic load steps from video decoding. |
Use Scenario: Providing 5V for display backlight, 3.3V for MCU, and "dying gasp" 12V hold-up for CAN bus communication during ignition-off transition. IC Role / Device Role / Timing Role: Primary power manager with LDO-controlled NPN driver delivering >100ms backup power after main supply loss. Use Value: Eliminates need for separate backup capacitor charging circuit; leverages integrated SHDN3 sequencing for graceful shutdown. |
| Telecom Line Card | TFT LCD Display Backlight |
|
Use Scenario: Delivering isolated 3.3V, 5V, and –5V rails (via external inverting charge pump) for FPGA I/O, PHY, and analog front-end in modular line cards. IC Role / Device Role / Timing Role: High-voltage input PMIC supporting hot-swap input stages and synchronized switching to meet EN55022 Class B emissions. Use Value: 36V max input withstands telecom surge transients; SYNC pin enables alignment with system master clock for deterministic noise shaping. |
Use Scenario: Driving LED strings requiring 12V boost output while powering display controller (3.3V) and touch interface (2.5V) from common 5V input. IC Role / Device Role / Timing Role: Integrated boost+buck+LDO controller eliminating discrete boost IC and linear regulators in display subassembly. Use Value: Achieves >85% efficiency at full brightness; independent soft-start prevents LED flash during panel initialization. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar triple-output DC/DC controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3775EUF#PBF | Two-phase synchronous buck controller only; no boost or LDO functions; requires external MOSFETs. | Targets high-current CPU/GPU rails only; lacks multi-topology integration for mixed-voltage systems. | Select when >10A buck output is required and boost/LDO are handled separately. |
| TPS65270RGET | Integrated dual buck + LDO (no boost); 2.95–6V input; lower voltage range and fixed 1.2MHz frequency. | Designed for portable applications (e.g., tablets); unsuitable for 24V industrial or automotive inputs. | Choose for cost-sensitive, low-input-voltage consumer electronics where boost is unnecessary. |
Compared with LTC3775EUF#PBF and TPS65270RGET, the LT3570IUF#TRPBF uniquely integrates buck, boost, and LDO control in one IC with 2.5–36V input support - making it the only option among the three for compact, wide-input, triple-rail industrial power systems requiring independent regulation and sequencing.
Availability
LT3570IUF#TRPBF is available at Aetrix Electronics and suitable for cable set-top boxes, automotive infotainment units, telecom line cards, and TFT LCD displays requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3570IUF#TRPBF 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 and maintains full technical and manufacturing continuity for legacy Linear power products.
The LT3570 belongs to Linear's high-voltage monolithic DC/DC controller family, designed specifically for industrial, automotive, and telecom applications demanding wide-input operation, multi-rail integration, and robust thermal performance in compact packages.
FAQ
What is the maximum input voltage rating for LT3570IUF#TRPBF?
The absolute maximum input voltage for VIN1, VIN2, and VIN3 pins is 40V. However, the recommended operating input voltage range is 2.5V to 36V per the datasheet specifications. Exceeding 36V may compromise long-term reliability even if within absolute maximum ratings, and the device is not characterized or guaranteed beyond 36V operation. LT3570IUF#TRPBF includes overtemperature protection but no input overvoltage clamp.
Can LT3570IUF#TRPBF operate with only the buck converter enabled?
Yes - LT3570IUF#TRPBF supports independent operation of each regulator. To enable only the buck converter, apply ≥1.4V to SHDN2 while holding SHDN1 and SHDN3 ≤0.3V. VIN2 must be present, and FB2 must be connected to the output via a resistor divider. The boost and LDO sections remain fully disabled, drawing only ≤1.5μA shutdown current. LT3570IUF#TRPBF retains full buck functionality including soft-start, frequency programming, and current limiting in this configuration.
What is the purpose of the BIAS pin on LT3570IUF#TRPBF?
The BIAS pin on LT3570IUF#TRPBF provides an optional auxiliary supply path for internal bias circuitry. When a voltage >2.5V is applied to BIAS, the IC draws quiescent current from this pin instead of VIN2, reducing power dissipation and improving efficiency in high-input-voltage applications. If BIAS is left unconnected or falls below 2.5V, LT3570IUF#TRPBF automatically reverts to sourcing bias current from VIN2. This feature is unique to the QFN package variants like LT3570IUF#TRPBF.
How does the LT3570IUF#TRPBF handle thermal overload conditions?
LT3570IUF#TRPBF incorporates thermal shutdown protection that disables all regulators when junction temperature exceeds ~150°C. Upon triggering, the device halts switching and enters a low-quiescent-current state until temperature falls below the hysteresis threshold (~135°C). During thermal shutdown, LT3570IUF#TRPBF does not latch off - it automatically recovers when cooled. Continuous operation above 125°C junction temperature is not recommended and may impair long-term reliability, as specified in the Absolute Maximum Ratings table.
Is LT3570IUF#TRPBF pin-compatible with other LT3570 variants?
Yes - LT3570IUF#TRPBF shares identical pinout and footprint with LT3570EUF#TRPBF, LT3570IUF#PBF, and LT3570EUF#PBF, all using the 24-lead 4mm × 4mm QFN package. The only differences are temperature grade (I-grade = –40°C to +125°C vs E-grade = 0°C to +125°C) and packaging (tape-and-reel #TRPBF vs tray #PBF). No PCB redesign is needed when substituting between these variants, and all share identical electrical characteristics except for guaranteed parametric performance over temperature.
LT3570IUF#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 24-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Topology:
- Step-Down (Buck) (1), Step-Up (Boost) (1), Linear (LDO) (1)
- Number of Outputs:
- 3
- Frequency - Switching:
- 500kHz ~ 2.1MHz
- Voltage/Current - Output 1:
- Adj to 0.8V, 1.5A
- Voltage/Current - Output 2:
- Adj to 0.8V, 1.5A
- Voltage/Current - Output 3:
- Controller
- w/LED Driver:
- No
- w/Supervisor:
- No
- w/Sequencer:
- No
- Voltage - Supply:
- 2.5V ~ 36V
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-QFN (4x4)
LT3570IUF#TRPBF FAQ
1.How can I place an order for LT3570IUF#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3570IUF#TRPBF 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 LT3570IUF#TRPBF reliable?
The price and inventory of LT3570IUF#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3570IUF#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3570IUF#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3570IUF#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3570IUF#TRPBF?
LT3570IUF#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3570IUF#TRPBF 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 LT3570IUF#TRPBF?
For technical support, including LT3570IUF#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3570IUF#TRPBF requirements.
6.How does Aetrix verify that LT3570IUF#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3570IUF#TRPBF 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 LT3570IUF#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3570IUF#TRPBF?
All LT3570IUF#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3570IUF#TRPBF, 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 LT3570IUF#TRPBF part is unused and in its original packaging.
Return procedure for LT3570IUF#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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