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Analog Devices Inc. LTC3778EF#PBF
- Part No.:
- LTC3778EF#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 20-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
LTC3778EF#PBF.pdf
- Description:
- IC REG CTRLR BUCK 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:573
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Product details
Overview
LTC3778EF#PBF from Analog Devices (formerly Linear Technology) is a valley-current-mode synchronous step-down DC/DC controller for high-efficiency, wide-input-voltage power supplies. It delivers 0.6V to 0.9×VIN output with ±1% reference accuracy, supports 4V–36V input, enables true current sensing without RSENSE, and features programmable soft-start, adjustable current limit, and output overvoltage protection. It is used in DDR memory power supplies and automotive DC power systems.
For engineers reviewing the LTC3778EF#PBF datasheet, LTC3778EF#PBF pinout, LTC3778EF#PBF application, or LTC3778EF#PBF equivalent, this page provides verified technical context, validated pin functions, confirmed operating parameters across temperature, real-world design meaning of key specs, and two rigorously validated alternative controllers for similar high-vin synchronous buck applications.
Technical Context
The LTC3778EF#PBF implements valley-current-mode control using an internal one-shot timer to set tON, enabling stable operation down to 2% duty cycle and tON(MIN) ≤ 100ns. Its SENSE+ and SENSE− pins support Kelvin sensing across either an optional external resistor or the bottom MOSFET's RDS(ON), eliminating sense-resistor losses.
Fault protection includes foldback current limiting, ±10% PGOOD window monitoring, output overvoltage shutdown (M1 off/M2 on), and input UVLO with hysteresis. The FCB pin selects forced continuous or discontinuous mode, while VRNG sets nominal current-sense voltage from 50mV to 200mV via resistive divider.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 4V to 36V - supports 12V/24V automotive rails and wide industrial inputs without pre-regulation. |
| Output Voltage Range | 0.6V to 0.9×VIN - enables direct regulation of DDR VDDQ (1.2V/1.35V) and core logic rails. |
| Reference Accuracy | ±1% at 0.6V - ensures tight output regulation critical for memory interface timing margins. |
| tON(MIN) | ≤100ns - enables high step-down ratios (e.g., 24V→1.2V at 200kHz) without pulse-skipping instability. |
| Switching Frequency | Adjustable via RON on ION pin - allows optimization between efficiency (low f) and size (high f). |
| Current Sense Threshold | 79–214mV range (programmable via VRNG) - supports precise current limiting with margin for RDS(ON) drift. |
| Shutdown IQ | ≤30µA - meets low-power standby requirements in battery-backed or always-on systems. |
Pinout & Package
Package: 20-lead 1mm-thin TSSOP (F package), RoHS-compliant, with exposed pad for thermal enhancement.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RUN/SS (1) | Run enable & soft-start ramp input | Capacitor-based ramp controls startup sequencing; <0.8V forces shutdown with ≤30µA IQ. |
| VON (2) | On-time comparator trip point | Configures tON proportionality to VOUT (e.g., tie to VOUT for constant frequency vs. load). |
| PGOOD (3) | Open-drain power-good flag | Pulled low when VFB exits ±10% window - enables system-level power sequencing and fault reporting. |
| VRNG (4) | Nominal sense voltage scaling input | Resistive divider from INTVCC sets 50–200mV nominal sense threshold - calibrates current limit for MOSFET RDS(ON). |
| ITH (5) | Error amplifier output & current threshold control | 0.8–2.4V range sets valley current limit; also serves as compensation node for loop stability. |
| FCB (6) | Forced continuous/discontinuous mode select | Ground = forced continuous (low-noise); INTVCC = discontinuous (light-load efficiency); divider = secondary-winding regulation assist. |
| SGND (7) | Signal ground reference | Star-point connection for feedback divider, compensation network, and small-signal components - isolates noise from PGND. |
| ION (8) | One-shot timer current input | Resistor from VIN sets switching frequency; internal 1µA bias enables VIN-compensated f-stability. |
| VFB (9) | Feedback input to error amplifier | Connects to resistive divider from VOUT; ±1% 0.6V reference enables accurate output regulation. |
| EXTVCC (10) | External VCC supply input | ≥4.7V disables internal 5V LDO and powers INTVCC directly - improves efficiency when secondary 5V rail is available. |
| VIN (11) | Main input supply | 4V–36V input path; requires RC filter (1Ω + 0.1µF) to SGND for EMI suppression and gate driver stability. |
| INTVCC (12) | Internal 5V regulator output | Powers internal logic and top/bottom gate drivers; requires ≥1µF low-ESR ceramic decoupling to PGND. |
| DRVCC (13) | Bottom gate driver supply | Typically tied to INTVCC via RC filter; requires ≥4.7µF low-ESR capacitor - supports up to 7V for enhanced gate drive. |
| BG (14) | Bottom N-MOSFET gate driver | Drives M2 gate from PGND to DRVCC; 1–2Ω pull-down/pull-up resistance enables fast turn-on/turn-off. |
| PGND (15) | Power ground return | Must connect to source of M2 or bottom of sense resistor - forms Kelvin sense return path and minimizes ground bounce. |
| SENSE− (16) | Current sense comparator (−) input | Kelvin connection to PGND or MOSFET source - rejects common-mode noise in high-dI/dt paths. |
| SENSE+ (17) | Current sense comparator (+) input | Connected to SW node (no RSENSE) or top of sense resistor - enables lossless sensing or precision current limiting. |
| SW (18) | Switch node | Connects to inductor, M1 drain, M2 source, and CB (−); swings from −0.3V to VIN - defines bootstrap charging path. |
| TG (19) | Top N-MOSFET gate driver | Drives M1 gate with swing = DRVCC superimposed on SW - requires bootstrap capacitor CB (0.22µF) between BOOST and SW. |
| BOOST (20) | Bootstrap capacitor (+) terminal | Swings from DRVCC−0.3V to VIN+DRVCC - charges CB during M2 conduction to sustain M1 gate drive. |
Key Features
| Feature | Design Value |
|---|---|
| No RSENSE operation | Uses bottom MOSFET RDS(ON) for current sensing - eliminates sense resistor cost, board space, and conduction losses. |
| True valley-current mode | Measures inductor current at valley point - provides inherent line/load transient immunity and stable light-load behavior. |
| Programmable current limit | VRNG and ITH pins allow full-range adjustment of current threshold - supports dynamic load profiling and fault margining. |
| Discontinuous/continuous mode selection | FCB pin enables user-selectable light-load operation - balances efficiency (discontinuous) vs. EMI/noise (continuous). |
| Stable with ceramic output capacitors | Compensated for low-ESR COUT - eliminates need for electrolytic or tantalum bulk caps, reducing size and improving reliability. |
| Micropower shutdown | IQ ≤ 30µA in shutdown - meets energy-star and automotive standby current requirements without external disable circuitry. |
Applications
| DDR Memory Power Supply | Automobile DC Power Supply |
|---|---|
Use Scenario: Regulating VDDQ (1.25V/1.35V) for DDR3/DDR4 memory subsystems in servers and telecom equipment. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing high-current, low-voltage output with tight transient response. Use Value: ±1% reference and valley-current mode ensure memory timing margins are maintained under rapid load steps up to 10A. |
Use Scenario: Converting 12V/24V vehicle battery to stable 3.3V/5V rails for infotainment, ADAS sensors, and telematics modules. IC Role / Device Role / Timing Role: High-input-voltage step-down controller with UVLO and OVP for automotive-grade power integrity. Use Value: 4V–36V input range and –40°C to 85°C operation meet ISO 16750-2 cold-crank and load-dump requirements. |
| Notebook and Palmtop Computers | Battery Chargers |
Use Scenario: Generating core voltage (e.g., 1.0V–1.8V) for CPU/GPU in portable computing devices with dynamic voltage scaling. IC Role / Device Role / Timing Role: Adaptive buck controller supporting variable output voltage via VID or DAC-controlled VFB divider. Use Value: Programmable soft-start and adjustable current limit prevent inrush damage during CPU frequency transitions. |
Use Scenario: Providing regulated 5V/12V output for USB-C PD or multi-cell Li-ion battery charging circuits. IC Role / Device Role / Timing Role: Primary DC/DC stage stepping down adapter voltage before linear or switching charger IC. Use Value: No RSENSE operation and ceramic-cap compatibility reduce BOM cost and improve thermal performance in compact chargers. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MP2918GQ-Z | Fixed 600kHz fSW; no VRNG pin; integrated MOSFET drivers only (no external FET control); 4.5V–28V VIN | Targeted at compact, fixed-frequency designs where layout simplicity outweighs programmability; lacks valley-current mode and RSENSE-free operation. | Choose MP2918GQ-Z for space-constrained, cost-sensitive consumer applications requiring minimal external components. |
| TPS53355DQPR | Dual-phase capable; integrated MOSFET drivers; 4.5V–25V VIN; uses average-current mode; no FCB or VRNG pins | Designed for multiphase CPU core rails; supports higher current via phase interleaving but lacks single-phase flexibility and wide-VIN capability. | Choose TPS53355DQPR when scaling beyond 30A or requiring phase-interleaved ripple reduction in server/desktop platforms. |
Compared with MP2918GQ-Z and TPS53355DQPR, the LTC3778EF#PBF uniquely combines wide 4V–36V input, valley-current control, RSENSE-free operation, and full programmability - making it optimal for high-reliability, variable-load, single-phase industrial and automotive buck converters where design flexibility and efficiency across load range are critical.
Availability
LTC3778EF#PBF is available at Aetrix Electronics and suitable for DDR memory power supplies, automobile DC power systems, and notebook computer voltage regulation requiring stable component supply, long-term lifecycle support, and guaranteed RoHS compliance.
Supply support for LTC3778EF#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 (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and aerospace markets.
The LTC3778EF#PBF belongs to Linear's high-voltage synchronous buck controller product line, designed specifically for efficient, flexible, and robust DC/DC conversion in demanding applications where input voltage varies widely and reliability is non-negotiable.
FAQ
What is the minimum on-time (tON(MIN)) specification for LTC3778EF#PBF, and why does it matter?
The LTC3778EF#PBF has a guaranteed tON(MIN) ≤ 100ns at TA = 25°C and ION = 180µA. This ultra-short minimum on-time enables stable operation at very high step-down ratios - for example, regulating 1.2V from a 24V input at 200kHz without pulse-skipping or subharmonic oscillation. It directly determines the lowest achievable output voltage at a given input and frequency, making LTC3778EF#PBF suitable for DDR and core logic rails in wide-input systems.
Can LTC3778EF#PBF operate without an external current-sense resistor?
Yes, the LTC3778EF#PBF supports true RSENSE-free operation by using the bottom N-channel MOSFET's RDS(ON) as the current-sensing element. Connect SENSE+ to the SW node and SENSE− to PGND. This configuration eliminates sense-resistor losses and cost, though it requires careful MOSFET selection to account for RDS(ON) variation with temperature - a key design consideration explicitly addressed in the LTC3778EF#PBF datasheet.
What is the function of the VRNG pin on LTC3778EF#PBF, and how is it used in practice?
The VRNG pin on LTC3778EF#PBF sets the nominal current-sense voltage threshold - ranging from 50mV to 200mV - via a resistive divider from INTVCC. For example, tying VRNG to 1V yields ~133mV nominal sense voltage. This allows precise calibration of the current limit to match the chosen MOSFET's RDS(ON) or external sense resistor value, accommodating manufacturing tolerances and thermal drift. The LTC3778EF#PBF datasheet provides the exact formula: VSENSE(MAX) ≈ 0.133 × VVRNG.
Does LTC3778EF#PBF support both continuous and discontinuous conduction modes?
Yes, LTC3778EF#PBF supports both modes via the FCB (Forced Continuous) pin. Tie FCB to ground for forced continuous mode (reducing EMI and aiding secondary-winding regulation), or to INTVCC for automatic discontinuous mode at light loads (improving efficiency). The device also includes a current-reversal comparator that detects zero inductor current and shuts off the bottom MOSFET, enabling natural DCM entry - a feature confirmed in the LTC3778EF#PBF functional diagram and operating description.
What thermal considerations apply to LTC3778EF#PBF in the 20-lead TSSOP package?
The LTC3778EF#PBF in the 20-lead TSSOP (F package) has θJA = 110°C/W and TJMAX = 125°C. To maintain reliable operation, the PCB must include adequate copper area under the exposed pad and thermal vias to inner/outer ground planes. At full load with 24V input, typical power dissipation is ~350mW; derating is required above 70°C ambient. The datasheet specifies guaranteed performance from 0°C to 70°C (E grade), with –40°C to 85°C assured by design correlation - all confirmed in the LTC3778EF#PBF absolute maximum and electrical characteristics tables.
LTC3778EF#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 4V ~ 36V
- Frequency - Switching:
- -
- Duty Cycle (Max):
- -
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Current Limit, Enable, Power Good, Soft Start
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-TSSOP
LTC3778EF#PBF FAQ
1.How can I place an order for LTC3778EF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3778EF#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 LTC3778EF#PBF reliable?
The price and inventory of LTC3778EF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3778EF#PBF is usually 5 days.
3.What payment methods are accepted for LTC3778EF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3778EF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3778EF#PBF?
LTC3778EF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3778EF#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 LTC3778EF#PBF?
For technical support, including LTC3778EF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3778EF#PBF requirements.
6.How does Aetrix verify that LTC3778EF#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3778EF#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 LTC3778EF#PBF meets industry standards.
7.What is the process for return or replacement of LTC3778EF#PBF?
All LTC3778EF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3778EF#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 LTC3778EF#PBF part is unused and in its original packaging.
Return procedure for LTC3778EF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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