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Analog Devices Inc. LTC3780IUH
- Part No.:
- LTC3780IUH
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 32-WFQFN Exposed Pad
- Datasheet:
-
LTC3780IUH.pdf
- Description:
- IC POWER MANAGEMENT
- Quantity:
- Payment:
- Shipping:
Inventory:1,625
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Product details
Overview
LTC3780IUH from Analog Devices (formerly Linear Technology) is a high-efficiency, synchronous 4-switch buck-boost DC/DC controller IC designed for single-inductor voltage regulation where input may be above, below, or equal to output. It delivers ±1% output voltage accuracy over 0.8V–30V range, supports 200kHz–400kHz phase-lockable switching frequency, and achieves up to 98% efficiency with quad N-channel MOSFET drive. It is used in automotive power systems requiring seamless mode transitions across wide VIN (4V–36V) and stable VOUT under dynamic load.
For engineers reviewing the LTC3780IUH datasheet, LTC3780IUH pinout, LTC3780IUH application, or LTC3780IUH equivalent, key selection criteria include its 32-pin QFN (5mm × 5mm) exposed-pad package, –40°C to +125°C operating junction temperature, FCB-selectable low-current modes (Burst Mode® in boost, skip-cycle in buck), and integrated 6V LDO for gate drive supply.
Technical Context
The LTC3780IUH implements constant-frequency current-mode control with dual-loop architecture: an inner current loop regulated via ITH voltage and outer voltage loop referenced to 0.800V at VOSENSE. Its four-switch topology enables continuous conduction across buck, buck-boost, and boost regions without discontinuity-mode transitions occur within 200ns and are determined by duty cycle and FCB pin state.
It features synchronous rectification using TG1/BG1 and TG2/BG2 drivers with <80ns dead-time control, internal foldback current limiting, output overvoltage protection (0.84V–0.88V trip at VOSENSE), and power-good monitoring with ±7.5% window. The PLLIN/PLLFLTR interface allows external synchronization or programmable frequency tuning from 170kHz to 440kHz.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 4V to 36V max - supports automotive cold-crank (4.5V) and load-dump (36V) transients without external protection. |
| VOUT Accuracy | ±1% over 0.8V–30V - ensures precise regulation for sensitive analog or digital loads without trimming. |
| Switching Frequency | 200kHz–400kHz (phase-lockable) - balances EMI, efficiency, and inductor size; adjustable via PLLFLTR voltage. |
| Efficiency | Up to 98% - achieved via synchronous N-MOSFET drive and low-loss current sensing with 120mV/–95mV thresholds. |
| Junction Temp Range | –40°C to +125°C - qualified for under-hood automotive and industrial environments per LTC3780I grade. |
| Package | 32-Lead QFN (5mm × 5mm) with exposed thermal pad - provides θJA = 34°C/W for high-power density thermal management. |
| PGOOD Threshold | ±7.5% of setpoint - enables reliable system-level power sequencing and fault detection in multi-rail supplies. |
Pinout & Package
Package: 32-Lead (5mm × 5mm) Plastic QFN with exposed thermal pad (Pin 33 = SGND). Requires soldering of exposed pad to PCB ground for electrical integrity and thermal performance (θJA = 34°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SENSE+ / SENSE– (Pins 1, 2) | Differential current sense inputs | Measure inductor current via external RSENSE; enable reverse-current detection and foldback limiting. |
| ITH (Pin 3) | Error amplifier output & current threshold control | Sets peak/valley current limits; clamped during soft-start; voltage range 0–2.4V defines trip points. |
| VOSENSE (Pin 4) | Voltage feedback input | Connects to resistor divider from VOUT; referenced to 0.800V internal bandgap for ±1% regulation. |
| SGND (Pin 5, Exposed Pad Pin 33) | Signal ground reference | Reference for all small-signal pins; must tie to PGND at single point to avoid noise coupling. |
| RUN (Pin 6) | Enable/disable control | Pull below 1.5V to shut down regulator; internal 100kΩ pull-down enables simple ON/OFF logic control. |
| FCB (Pin 7) | Operating mode selector | Voltage selects forced continuous (0–0.75V), skip-cycle/burst (0.85–5V), or DCM (≥5.3V) - no external logic required. |
| PLLFLTR (Pin 8) | PLL low-pass filter node | DC voltage sets oscillator frequency (170–440kHz); AC signal enables external synchronization via PLLIN. |
| PLLIN (Pin 10) | External sync input | 50kΩ internal termination to SGND; rising edge synchronizes bottom-gate clock to external source. |
| STBYMD (Pin 11) | LDO keep-alive control | Enables INTVCC during RUN=low for wake-up circuitry; bypass with 0.1µF to SGND for always-on LDO. |
| BOOST1 / BOOST2 (Pins 14, 27) | Floating gate drive supplies | Provide bootstrapped voltage for TG1/TG2; swing from diode-drop below INTVCC to VIN+INTVCC or VOUT+INTVCC. |
| TG1 / TG2 (Pins 15, 26) | Top N-MOSFET gate drivers | Drive high-side switches with INTVCC-referenced swing; 50ns rise/fall time supports 400kHz operation. |
| SW1 / SW2 (Pins 17, 24) | Switch node connections | Interface to inductor center-tap; SW1 connects to VOUT side, SW2 to VIN side - defines buck/boost path. |
| BG1 / BG2 (Pins 18, 20) | Bottom N-MOSFET gate drivers | Drive low-side switches from PGND to INTVCC; 45ns rise/55ns fall time minimizes shoot-through risk. |
| PGND (Pin 19) | Power ground return | Return path for MOSFET sources, CIN, and CVCC; must be tightly coupled to layout for low-noise current sensing. |
| INTVCC (Pin 21) | Internal 6V LDO output | Supplies gate drivers and control circuits; regulated to 5.7–6.3V with 0.2–2% load regulation. |
| EXTVCC (Pin 22) | External bias input | Switches internal LDO off when >5.7V; reduces power loss in high-VIN applications; max 7V rating. |
| VIN (Pin 23) | Main input supply | Accepts 4–36V; requires RC filter (1Ω + 0.1µF) to damp high-frequency noise from switching nodes. |
| SS (Pin 31) | Soft-start timing capacitor | Controls inrush current ramp rate; minimum 6.8nF recommended to prevent overshoot and stress on input caps. |
| PGOOD (Pin 30) | Open-drain power-good flag | Asserts low when VOUT deviates >±7.5% from setpoint - used for sequencing, reset generation, or fault logging. |
Key Features
| Feature | Design Value |
|---|---|
| Single-inductor buck-boost topology | Eliminates need for separate buck/boost converters or transformer-based solutions in wide-input-range systems. |
| Quad N-channel MOSFET synchronous drive | Enables high-efficiency (>95% at 5A) without external level-shifters or P-channel devices. |
| Seamless mode transition | Zero-crossing between buck, buck-boost, and boost occurs within 200ns - no output glitch or regulation loss. |
| Adjustable soft-start with current ramping | Prevents input surge current during startup; controlled via external SS capacitor value and internal 1.2µA charge current. |
| Integrated 6V LDO with EXTVCC switchover | Reduces BOM count and improves efficiency at high VIN by automatically sourcing gate drive from external supply. |
| Output disconnect during shutdown | VOUT is isolated from VIN when RUN=low - prevents backfeed into input rail in battery-powered or redundant systems. |
Applications
| Automotive Power Management | Telecom DC Distribution |
|---|---|
Use Scenario: Regulating 12V battery-derived supply to stable 5V/3.3V for infotainment ECUs during cold-crank (4.5V) and load-dump (36V) events. IC Role / Device Role / Timing Role: 4-switch buck-boost controller maintaining regulation across full automotive voltage range with no manual mode switching. Use Value: Eliminates need for pre-regulator stages or wide-input LDOs; ±1% accuracy ensures compliance with AEC-Q100 functional safety requirements. | Use Scenario: Converting –48V telecom rectified bus to +12V intermediate rail for PoE switches and baseband processors. IC Role / Device Role / Timing Role: High-efficiency synchronous controller driving discrete N-MOSFETs to deliver >10A with minimal heat dissipation in compact chassis. Use Value: 98% peak efficiency reduces cooling requirements; phase-lockable frequency avoids beat frequencies with upstream AC-DC converters. |
| Industrial Battery Systems | High-Power Portable Equipment |
Use Scenario: Managing Li-ion pack (9–32V) to fixed 15V output for motor drives and PLC I/O modules with variable load profiles. IC Role / Device Role / Timing Role: Current-mode controller with FCB-selectable Burst Mode® and skip-cycle operation for >90% light-load efficiency. Use Value: Extends runtime in standby; foldback current limiting protects against short-circuit faults without external circuitry. | Use Scenario: Powering FPGA and ADC subsystems in portable test equipment where input varies from 10V (AC adapter) to 28V (LiFePO₄ battery). IC Role / Device Role / Timing Role: Single-chip solution delivering stable 1.2V/3.3V/5V rails with independent soft-start and PGOOD sequencing. Use Value: Reduces board area vs. multiple regulators; exposed-pad QFN enables thermal design for 5W+ dissipation in handheld enclosures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck-boost controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8705IUHF#PBF | Wider VIN range (2.8V–80V), integrated current sense amp, no FCB pin - uses MODE pin for burst/skip/CCM. | Supports higher input voltages (e.g., 48V industrial buses); lacks direct FCB-equivalent for per-mode low-power optimization. | Select LT8705 for >40V input or when integrated current sensing simplifies layout; LTC3780IUH preferred for cost-sensitive 4–36V designs with fine-grained low-load control. |
| MPQ4312GR-A | Monolithic 4-switch buck-boost (integrated MOSFETs), 3.3–40V input, fixed 300kHz, no PLL sync or EXTVCC switchover. | Lower BOM count but limited to ≤3A output; no external frequency programming or thermal pad for >2W dissipation. | Select MPQ4312 for space-constrained <3A applications where integration outweighs efficiency flexibility; LTC3780IUH retains advantage for >5A, high-temp, or synchronized multi-rail systems. |
Compared with LT8705IUHF#PBF and MPQ4312GR-A, the LTC3780IUH offers superior thermal performance via exposed-pad QFN, precise ±1% VOUT accuracy across full temperature range, and dedicated FCB pin enabling independent low-power mode selection for buck and boost - critical for battery longevity in mixed-mode operation.
Availability
LTC3780IUH is available at Aetrix Electronics and suitable for automotive power management, telecom DC distribution, and industrial battery systems requiring stable component supply with guaranteed long-term availability and traceable sourcing.
Supply support for LTC3780IUH 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, datasheets, and application engineering for legacy Linear parts including the LTC3780 series.
The LTC3780 product line was designed specifically for high-efficiency, wide-input-range DC/DC conversion in automotive, industrial, and telecom infrastructure where seamless buck-boost operation and robust fault protection are mandatory.
FAQ
What is the maximum operating junction temperature for the LTC3780IUH?
The LTC3780IUH is rated for a junction temperature range of –40°C to +125°C, consistent with its "I" grade qualification. This specification is verified per the Absolute Maximum Ratings table and supported by thermal characterization data showing θJA = 34°C/W for the 32-lead QFN package. Derating curves in the datasheet confirm stable operation across this full range when PCB thermal design meets recommended copper area and via guidelines for the exposed pad.
Does the LTC3780IUH support external frequency synchronization?
Yes, the LTC3780IUH supports external synchronization via the PLLIN pin (Pin 10), which accepts a logic-level clock input with internal 50kΩ termination to SGND. When driven, the phase-locked loop forces the rising edge of the bottom-gate driver signal to align with the PLLIN rising edge. This capability enables deterministic timing across multiple converters in noise-sensitive or EMI-constrained systems, and is fully documented in the Electrical Characteristics and Typical Performance sections of the LTC3780 datasheet.
How does the FCB pin affect operating mode selection in the LTC3780IUH?
The FCB pin (Pin 7) directly determines low-current behavior: at 0–0.75V it enables forced continuous conduction mode in both buck and boost; at 0.85–5V it selects skip-cycle mode in buck and Burst Mode® in boost; and at ≥5.3V it activates constant-frequency discontinuous mode. These thresholds are specified in the Electrical Characteristics table and validated across temperature. No external logic is needed - simple resistor dividers or GPIO outputs suffice for mode control.
What is the purpose of the STBYMD pin on the LTC3780IUH?
The STBYMD pin (Pin 11) controls whether the internal 6V LDO remains active during RUN-pin shutdown. When pulled to ground, it disables the LDO and pulls SS low to prevent restart. When biased between 2V–5V (e.g., via resistor divider from VIN), it keeps INTVCC powered to support external wake-up circuitry - a key feature for low-power automotive modules needing controlled reactivation without full system reset. This behavior is explicitly defined in the Pin Functions section.
Can the LTC3780IUH operate with input voltage equal to output voltage?
Yes, the LTC3780IUH is explicitly designed for buck-boost operation where VIN ≈ VOUT. Its four-switch architecture enables seamless transition through the buck-boost region without regulation loss or output disturbance, with typical mode-transition time of 200ns. This capability is confirmed in the Block Diagram, Operation section, and Figure 2 (Operating Mode vs Duty Cycle), making it suitable for applications like 12V-to-12V regulation with input transients.
LTC3780IUH Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 32-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Obsolete
- Output Type:
- Transistor Driver
- Function:
- Step-Up/Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck-Boost
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 4V ~ 30V
- Frequency - Switching:
- 200kHz ~ 400kHz
- Duty Cycle (Max):
- 99%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Current Limit, Enable, Power Good, Soft Start
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 32-QFN (5x5)
LTC3780IUH FAQ
1.How can I place an order for LTC3780IUH through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3780IUH 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 LTC3780IUH reliable?
The price and inventory of LTC3780IUH are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3780IUH is usually 5 days.
3.What payment methods are accepted for LTC3780IUH?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3780IUH transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3780IUH?
LTC3780IUH orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3780IUH 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 LTC3780IUH?
For technical support, including LTC3780IUH datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3780IUH requirements.
6.How does Aetrix verify that LTC3780IUH is sourced from the original manufacturer or authorized distributors?
All LTC3780IUH 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 LTC3780IUH meets industry standards.
7.What is the process for return or replacement of LTC3780IUH?
All LTC3780IUH units undergo pre-shipment inspection (PSI). If there is an issue with LTC3780IUH, 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 LTC3780IUH part is unused and in its original packaging.
Return procedure for LTC3780IUH:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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