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Analog Devices Inc. LT3570EUF#TRPBF
- Part No.:
- LT3570EUF#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Voltage Regulators - Linear + Switching
- Package:
- 24-WFQFN Exposed Pad
- Datasheet:
-
LT3570EUF#TRPBF.pdf
- Description:
- IC REG TRIPLE BUCK/BST/LNR 24QFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,812
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Product details
Overview
LT3570EUF#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 systems in telecom and automotive "dying gasp" backup supplies.
For engineers reviewing the LT3570EUF#TRPBF datasheet, LT3570EUF#TRPBF pinout, LT3570EUF#TRPBF application, or LT3570EUF#TRPBF equivalent, key selection criteria include independent shutdown control per regulator, dual soft-start capability, 24-lead 4mm × 4mm QFN package with exposed thermal pad, and verified 1.5A current limit on both SW1 and SW2 switches under full temperature range.
Technical Context
The LT3570EUF#TRPBF implements constant-frequency current-mode control for both buck and boost regulators, each with dedicated error amplifiers (A1/A2), VC compensation pins, and independent feedback (FB1/FB2) referenced to 788mV. The LDO controller drives an external NPN via NPN_DRV with up to 10mA base current and uses FB3 for 788mV-regulated output voltage setting.
Its architecture supports synchronization up to 2.75MHz via SYNC pin, programmable frequency (500kHz–2.1MHz) via RT resistor, and separate VIN supplies: VIN1 powers only the boost stage, VIN2 powers the buck stage and internal circuitry, and VIN3 powers the LDO controller - enabling flexible rail sequencing and isolation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.5V to 36V - supports wide industrial and automotive supply rails without pre-regulation. |
| Switch Current Limit (SW1/SW2) | 1.5A min - guarantees sustained 1A output at VOUT2 = 3.3V with proper inductor selection. |
| Feedback Reference Voltage | 788mV ±12mV - enables precise output programming with standard resistor dividers. |
| Switching Frequency Range | 500kHz to 2.1MHz - allows compact magnetics and noise avoidance in sensitive RF bands. |
| Soft-Start Control | Independent SS1/SS2 pins - prevents inrush current and output overshoot during power-up of each converter. |
| LDO Controller Output | Up to 10mA base drive - sufficient to bias external NPN transistors for high-current linear regulation. |
| Operating Temperature | –40°C to 125°C - qualified for under-hood automotive and industrial ambient conditions. |
Pinout & Package
LT3570EUF#TRPBF is housed in a 24-lead (4mm × 4mm) plastic QFN package with exposed thermal pad (Pin 25) that must be soldered to PCB ground for thermal and electrical integrity. Pin count, layout, and function mapping are identical across E-grade and I-grade variants in this package.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN2 (Pins 1,2) | Buck Regulator Input & Internal Bias Supply | Powers buck stage and core logic; requires local 10μF X7R ceramic bypass. |
| SW2 (Pin 3) | Buck Switch Node (NPN Emitter) | Connects to inductor/diode; handles peak currents up to 1.5A with <240mV saturation. |
| SW1 (Pin 4) | Boost Switch Node (NPN Collector) | Connects to boost inductor/diode; rated for 40V max, 1.5A current limit. |
| GND (Pins 5,6,16,25) | Ground Reference & Thermal Path | Multiple GND pins + exposed pad ensure low-impedance return and thermal dissipation. |
| VIN1 (Pin 7) | Boost Regulator Input | Supplies only boost stage; decoupled separately to avoid coupling noise into buck path. |
| SS1 (Pin 8) | Boost Soft-Start Control | Sinks 4.5μA to charge external capacitor; ramps reference to prevent overshoot. |
| VC1 (Pin 9) | Boost Error Amplifier Compensation | Connect RC network to ground for loop stability; threshold ~750mV. |
| FB1 (Pin 10) | Boost Feedback Input | Regulated to 788mV; sets VOUT1 via resistor divider (e.g., 12V with 10.2k/1.02k). |
| SHDN1 (Pin 11) | Boost Enable Control | Active-high (>1.4V); independent enable/disable of boost converter only. |
| SHDN2 (Pin 12) | Buck Enable Control | Active-high (>1.4V); independent control of buck stage without affecting others. |
| SHDN3 (Pin 13) | LDO Controller Enable | Active-high (>1.5V); enables NPN_DRV and FB3 regulation path. |
| SYNC (Pin 14) | External Clock Synchronization | Accepts 650kHz–2.75MHz clock; locks oscillator phase to system timing source. |
| RT (Pin 15) | Frequency Set Resistor | Resistor to GND sets fSW: 44.2k → 500kHz, 7.87k → 2.1MHz. |
| SS2 (Pin 17) | Buck Soft-Start Control | Identical function to SS1 but for buck regulator; enables staggered startup. |
| VC2 (Pin 18) | Buck Error Amplifier Compensation | RC compensation node for buck loop; switching threshold ~700mV. |
| FB2 (Pin 19) | Buck Feedback Input | Regulated to same 788mV reference as FB1; sets VOUT2 (e.g., 3.3V with 22k/10k). |
| FB3 (Pin 20) | LDO Controller Feedback | 788mV reference for external NPN-based linear regulator; sets VOUT3 (e.g., 2.5V). |
| NPN_DRV (Pin 21) | External NPN Base Drive | Delivers up to 10mA sourced from VIN3; drives base of external pass transistor. |
| VIN3 (Pin 22) | LDO Controller Input | Supplies only NPN_DRV and FB3 path; bypassed locally for clean bias. |
| BIAS (Pin 23) | Internal Circuitry Bias Supply | Optional lower-voltage bias source (>2.5V); reduces quiescent power vs. VIN2. |
| BOOST (Pin 24) | Buck NPN Driver Boost Rail | Charged via external Schottky diode; provides >VIN2 voltage to saturate internal NPN. |
Key Features
| Feature | Design Value |
|---|---|
| Triple independent regulation paths | Buck (VOUT2), boost (VOUT1), and LDO controller (VOUT3) with separate SHDN, SS, and FB pins enable true rail independence and sequencing. |
| High-frequency operation up to 2.1MHz | Enables use of sub-4.7μH inductors and 10μF ceramic output capacitors - reducing solution size by >40% vs. 500kHz designs. |
| Programmable soft-start per converter | SS1/SS2 pins allow controlled ramp-up of each output, eliminating cross-regulation issues and inrush stress on shared input sources. |
| Separate input supplies per function | VIN1 (boost only), VIN2 (buck + logic), VIN3 (LDO controller) permit optimized power routing and fault isolation in multi-battery systems. |
| Robust thermal design | 24-lead QFN with exposed pad achieves θJA = 37°C/W - supports 1.5A continuous operation at 125°C junction without derating. |
Applications
| Cable Set-Top Box Power | Automotive Dying Gasp Backup |
|---|---|
Use Scenario: Powering multiple rails (12V tuner, 3.3V SoC, 2.5V memory) from a single 12V battery or wall adapter in compact consumer enclosures. IC Role / Device Role / Timing Role: Primary triple-output DC/DC controller managing all conversion stages with independent enable and soft-start. Use Value: Eliminates need for three discrete converters; reduces BOM count by ≥7 components and PCB area by >35% versus discrete solutions. |
Use Scenario: Maintaining critical communication during vehicle ignition-off events using supercapacitor or small backup battery. IC Role / Device Role / Timing Role: Buck-boost-LDO controller generating stable 3.3V/5V/12V rails from decaying 6–16V backup source. Use Value: Independent shutdown of non-critical rails extends backup runtime; 2.5V–36V input range accommodates wide supercap voltage swing. |
| TFT LCD Display Supply | Telecom Line Card Bias |
Use Scenario: Generating AVDD (12V), VGH (18–20V), and VGL (–7V) for TFT panel drivers from a 5V or 12V board supply. IC Role / Device Role / Timing Role: Dual-switching regulator providing positive boost and buck outputs; FB3 used for gate driver bias control. Use Value: Single-chip solution replaces discrete boost + buck + LDO; 2.1MHz operation avoids audible noise in display audio circuits. |
Use Scenario: Providing isolated bias voltages (±12V, 3.3V) for analog front-end and line interface ICs in DSL or PON equipment. IC Role / Device Role / Timing Role: Multi-rail controller delivering primary bias rails while supporting hot-swap sequencing and brownout detection. Use Value: SHDN1/SHDN2/SHDN3 allow staged power-up/down per subsystem; wide input range tolerates fluctuating telecom -48V derived rails. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar multi-rail DC/DC controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3892-2 | Two-phase synchronous buck controller (no boost/LDO); supports up to 60V input; requires external MOSFETs. | Targets higher-efficiency, higher-current buck-only applications; lacks integrated boost or LDO controller functionality. | Select when >1.5A buck output or >95% efficiency is required; not suitable for boost or NPN-LDO topologies. |
| TPS65270 | Dual buck + LDO (no boost); 2.95–18V input; integrated MOSFETs; fixed 3.3V/1.2V LDOs; no external NPN drive. | Designed for low-voltage digital SoCs; lacks boost capability and programmable LDO output; limited to 18V max input. | Choose for cost-sensitive, low-input-voltage embedded systems where boost is unnecessary and fixed LDOs suffice. |
Compared with LTC3892-2 and TPS65270, the LT3570EUF#TRPBF uniquely integrates buck, boost, and NPN-LDO controller in one 24-pin QFN - offering unmatched functional density for 2.5–36V multi-rail systems requiring >12V outputs and external pass transistor flexibility.
Availability
LT3570EUF#TRPBF is available at Aetrix Electronics and suitable for cable set-top boxes, automotive dying-gasp systems, and telecom line cards requiring stable component supply across extended temperature and long production lifecycles.
Supply support for LT3570EUF#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 product support, datasheet documentation, and application engineering for legacy Linear parts including the LT3570 series.
The LT3570 belongs to Linear's high-voltage monolithic DC/DC controller family, designed specifically for space-constrained, multi-rail industrial and automotive power systems requiring wide input range and independent regulation paths.
FAQ
What is the maximum supported switching frequency for LT3570EUF#TRPBF?
The LT3570EUF#TRPBF supports a programmable switching frequency from 500kHz to 2.1MHz using the RT pin resistor, and can be synchronized to an external clock up to 2.75MHz. At RT = 7.87kΩ, the typical frequency is 2.1MHz - enabling compact magnetics and reduced output ripple in space-constrained designs.
Does LT3570EUF#TRPBF integrate power MOSFETs or bipolar transistors?
Yes, the LT3570EUF#TRPBF integrates two internal NPN bipolar power switches: SW1 (boost, collector-connected) and SW2 (buck, emitter-connected), each with a guaranteed minimum current limit of 1.5A and VCE(SAT) ≤ 240mV at 1A. No external MOSFETs are required for either switching path.
Can LT3570EUF#TRPBF generate negative output voltages?
No, the LT3570EUF#TRPBF does not support inverting (buck-boost or Cuk) topologies natively. Its boost converter generates only positive outputs above VIN1, and its buck and LDO controller paths are strictly positive-output. Negative rails require external inverting charge-pump or flyback circuitry.
What is the purpose of the BIAS pin on LT3570EUF#TRPBF?
The BIAS pin on LT3570EUF#TRPBF provides an optional lower-voltage supply (≥2.5V) for internal circuitry, reducing power dissipation compared to drawing bias current from VIN2. If BIAS falls below 2.5V, the device automatically reverts to VIN2 for bias - ensuring robust operation across varying input conditions.
Is LT3570EUF#TRPBF pin-compatible with other LT3570 variants like LT3570EFE#TRPBF?
No, LT3570EUF#TRPBF (24-lead QFN) is not pin-compatible with LT3570EFE#TRPBF (20-lead TSSOP). While both share identical electrical functionality and signal naming, their pin counts, layouts, and thermal pad configurations differ - requiring separate PCB footprints and layout validation.
LT3570EUF#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)
LT3570EUF#TRPBF FAQ
1.How can I place an order for LT3570EUF#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3570EUF#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 LT3570EUF#TRPBF reliable?
The price and inventory of LT3570EUF#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3570EUF#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3570EUF#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3570EUF#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3570EUF#TRPBF?
LT3570EUF#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3570EUF#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 LT3570EUF#TRPBF?
For technical support, including LT3570EUF#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3570EUF#TRPBF requirements.
6.How does Aetrix verify that LT3570EUF#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3570EUF#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 LT3570EUF#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3570EUF#TRPBF?
All LT3570EUF#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3570EUF#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 LT3570EUF#TRPBF part is unused and in its original packaging.
Return procedure for LT3570EUF#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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