My Inquiry
My Account
Analog Devices Inc. LTC3785IUF#TRPBF
- Part No.:
- LTC3785IUF#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 24-WFQFN Exposed Pad
- Datasheet:
-
LTC3785IUF#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK-BOOST 24QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,896
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
LTC3785IUF#TRPBF from Analog Devices (formerly Linear Technology) is a high-efficiency, synchronous, no-RSENSE buck-boost DC/DC controller driving four external N-channel MOSFETs. It operates across 2.7V–10V input and output ranges, supports VIN above/below/equal to VOUT, delivers up to 10A output current, and achieves up to 96% efficiency in handheld Li-Ion-powered systems such as cellular telephones and wireless modems.
For engineers reviewing the LTC3785IUF#TRPBF datasheet, LTC3785IUF#TRPBF pinout, LTC3785IUF#TRPBF application, or LTC3785IUF#TRPBF equivalent, key selection criteria include its single-inductor architecture, programmable 100kHz–1MHz switching frequency, true output disconnect during shutdown, foldback current limit, and integrated overvoltage/undervoltage protection with ±6.5% UV and +10% OV thresholds relative to 1.225V FB reference.
Technical Context
The LTC3785IUF#TRPBF implements a voltage-mode, four-switch buck-boost topology with drain-to-source current sensing (No RSENSE™) for both forward and reverse current limiting. Its control loop uses an internal 1.225V reference and error amplifier output (VC) to directly determine switch duty cycles across buck, buck-boost, and boost regions.
It features independent gate drivers for all four N-MOSFETs with 2Ω driver impedance, nonoverlap timing (100ns), and dual floating bootstrap supplies (VBST1/VBST2) supporting high-side drive for switches A and D. Burst Mode® operation is user-enabled via MODE pin and reduces quiescent current to 86µA at light loads.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input/Output Range | 2.7V to 10V - supports single/dual-cell Li-Ion, alkaline/NiMH, and wide-input industrial rails without level-shifting. |
| Max Output Current | 10A - enables high-power portable applications like palmtop computers and handheld instruments. |
| Efficiency | Up to 96% - achieved using synchronous rectification and low-loss No RSENSE™ current sensing. |
| Switching Frequency | 100kHz to 1MHz - set by RT resistor; allows optimization of size (high-f) vs EMI/noise (low-f). |
| FB Reference Voltage | 1.225V ±25mV - precise internal reference enabling accurate output regulation from 2.7V to 10V. |
| UV/OV Thresholds | −6.5% UV / +10% OV on FB - provides robust fault protection with 1.5% hysteresis; configurable via VSENSE divider. |
| Operating Temp | −40°C to +125°C - qualified for automotive and industrial environments requiring extended junction temperature range. |
Pinout & Package
Package: 24-lead (4mm × 4mm) plastic QFN with exposed pad (Pin 25 = GND). Thermal performance requires soldering exposed pad to PCB ground plane.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RUN/SS (1) | Enable & soft-start control | Internal 1µA charge source; clamps VC during startup; discharges on fault to trigger latch-off or recycle after 32× soft-start time. |
| VC (2) | Error amplifier output | Loop compensation node; connects to FB via RC network; clamped by RUN/SS during soft-start. |
| FB (3) | Feedback input | Compares output divider voltage to 1.225V reference; sets regulated VOUT = 1.225V × (R1+R2)/R2. |
| VSENSE (4) | OV/UV sense input | Monitors overvoltage (+10%) and undervoltage (−6.5%) relative to FB; allows threshold tuning via external divider. |
| ILSET (5) | Current limit programming | Resistor to GND sets forward current limit threshold (e.g., 55–155mV) for ISVIN–ISSW1 sensing. |
| CCM (6) | Continuous conduction mode control | Low = −15mV reverse limit; High = symmetric forward/reverse limit - enables ideal diode or bidirectional operation. |
| RT (7) | Oscillator frequency set | Resistor to GND programs fOSC ≈ 25 MHz / RT(kΩ); e.g., 49.9kΩ → ~500kHz. |
| MODE (8) | Burst Mode enable | High = variable-frequency Burst Mode (86µA IQ); Low = fixed-frequency operation (1.5mA IQ). |
| NC (9) | No connect | No internal connection; must be left unconnected or tied to GND per layout best practice. |
| ISVOUT (10) | Reverse current sense (+) | Connects to drain of boost-side N-MOSFET D (TG2); used with ISSW2 for reverse current detection. |
| VBST2 (11) | Boost supply for TG2 | Floating supply for top gate driver D; swings up to VOUT + VCC – Vdiode; requires 0.1–0.47µF X5R/X7R capacitor. |
| TG2 (12) | Top gate driver D | Drives gate of N-MOSFET D referenced to SW2; swing = VCC – Vdiode superimposed on SW2 node. |
| SW2 (13) | Switch node D/C common | Ground reference for TG2/BG2; connects to sources of switches C and D; critical for layout symmetry and noise immunity. |
| ISSW2 (14) | Reverse current sense (−) | Connects to source of N-MOSFET D (TG2); forms differential pair with ISVOUT for reverse current monitoring. |
| BG2 (15) | Bottom gate driver C | Drives gate of N-MOSFET C referenced to SW2; complements TG2 in boost-phase synchronous rectification. |
| VDRV (16) | Driver supply | Connects to VCC; powers ground-referenced drivers BG1/BG2 and logic; bypass with ≥4.7µF ceramic cap. |
| BG1 (17) | Bottom gate driver B | Drives gate of N-MOSFET B referenced to SW1; complements TG1 in buck-phase synchronous rectification. |
| ISSW1 (18) | Forward current sense (−) | Connects to source of N-MOSFET A (TG1); forms differential pair with ISVIN for input current limiting. |
| SW1 (19) | Switch node A/B common | Ground reference for TG1/BG1; connects to sources of switches A and B; defines buck-phase switching node. |
| TG1 (20) | Top gate driver A | Drives gate of N-MOSFET A referenced to SW1; swing = VCC – Vdiode superimposed on SW1 node. |
| VBST1 (21) | Boost supply for TG1 | Floating supply for top gate driver A; swings up to VIN + VCC – Vdiode; requires 0.1–0.47µF X5R/X7R capacitor. |
| ISVIN (22) | Forward current sense (+) | Connects to drain of buck-side N-MOSFET A (TG1); used with ISSW1 for input current limiting. |
| VCC (23) | Internal LDO output | 4.35V ±200mV regulated supply for drivers and core logic; max 100mA peak; bypass with ≥4.7µF ceramic cap. |
| VIN (24) | Main input supply | Input to VCC LDO; supports 2.7V–10V; requires ≥10µF ceramic decoupling near pin. |
| GND (25) | Power & signal ground | Exposed thermal pad; electrically connected to PGND; must be soldered to PCB ground plane for thermal and EMI performance. |
Key Features
| Feature | Design Value |
|---|---|
| Single-inductor buck-boost topology | Enables compact power conversion where VIN may be above, below, or equal to VOUT - eliminates need for separate buck/boost stages. |
| No RSENSE™ current sensing | Uses MOSFET RDS(ON) for forward/reverse current limit detection - avoids power loss and board space of discrete sense resistors. |
| True output disconnect | Internally disables all switches during shutdown - prevents backfeed from VOUT to VIN, critical for battery-backed systems. |
| Programmable burst mode | Reduces light-load IQ to 86µA while maintaining regulation - extends battery life in portable devices without compromising transient response. |
| Integrated OV/UV protection | Hardware-based comparators with ±6.5%/+10% thresholds on FB reference - provides fast, reliable fault response independent of control loop. |
| Four-switch synchronous drive | Independent TG1/BG1/TG2/BG2 outputs with 2Ω drivers and 100ns nonoverlap - maximizes efficiency and minimizes shoot-through risk. |
Applications
| Cellular Telephones | Wireless Modems |
|---|---|
Use Scenario: Power management in 4G/5G handsets with dual-cell Li-Ion (3.0V–8.4V) supplying 3.3V or 5V system rails. IC Role / Device Role / Timing Role: Primary buck-boost controller regulating core voltage under dynamic load and varying battery state-of-charge. Use Value: Maintains stable 3.3V/5V output across full battery discharge curve (8.4V→3.0V) with >94% efficiency at 2A, reducing thermal stress and extending talk time. | Use Scenario: Compact LTE/WiMAX modem module powered by single-cell Li-Ion (2.7V–4.2V) delivering 3.3V RF and baseband supplies. IC Role / Device Role / Timing Role: Single-stage DC/DC converter enabling direct battery-to-3.3V conversion without intermediate regulators. Use Value: Eliminates cascaded buck + LDO architecture, saving >30% board area and improving full-load efficiency by 8–10 percentage points versus linear solutions. |
| Palmtop Computers | Handheld Instruments |
Use Scenario: Main power rail generation in ruggedized PDAs with multicell alkaline/NiMH (4.8V–9V) powering 3.3V microprocessor and peripherals. IC Role / Device Role / Timing Role: High-current (up to 10A) buck-boost controller supporting burst-mode CPU load transients and deep-sleep states. Use Value: Delivers 96% peak efficiency at 5A and drops to 86µA quiescent current in Burst Mode - enabling >12-hour runtime on AA batteries. | Use Scenario: Portable multimeter or oscilloscope with dual-cell Li-Ion (3.0V–8.4V) powering mixed-signal analog front-end and digital processing core. IC Role / Device Role / Timing Role: Precision-regulated 3.3V/5V supply with low-noise fixed-frequency mode for ADC reference and high-efficiency Burst Mode for display backlight control. Use Value: Achieves <15mVpp output ripple in fixed-frequency mode and <50mVpp in Burst Mode - meeting EN61000-4-3 radiated emission limits for Class B equipment. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck-boost controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8705EFE#PBF | Wider 2.8V–80V input, integrated gate drivers, no ILSET pin - uses current-sense resistor instead of RDS(ON) sensing. | Targeted at industrial/high-voltage DC/DC; lacks No RSENSE™ benefit and true output disconnect. | Choose LT8705 when input exceeds 10V or when design requires >80V fault tolerance; avoid if minimizing BOM count and board area is critical. |
| MPQ4332GJ-AEC1-P | Automotive-grade (AEC-Q100), 3.3V–36V input, integrated MOSFETs (4A), fixed 2.2MHz fSW, no programmable Burst Mode. | Designed for infotainment and ADAS; not suitable for >10A or ultra-low-IQ portable applications. | Choose MPQ4332 for automotive 12V systems needing qualification and integration; avoid for battery-powered handhelds requiring <100µA IQ or >6A output. |
Compared with LT8705EFE#PBF and MPQ4332GJ-AEC1-P, the LTC3785IUF#TRPBF uniquely combines No RSENSE™ current sensing, true output disconnect, programmable Burst Mode, and 2.7V–10V optimization - making it the only choice for high-efficiency, space-constrained, single/dual-cell Li-Ion applications demanding minimal external components and guaranteed shutdown isolation.
Availability
LTC3785IUF#TRPBF is available at Aetrix Electronics and suitable for cellular telephones, wireless modems, and handheld instruments requiring stable component supply with guaranteed long-term availability and full industrial temperature support.
Supply support for LTC3785IUF#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, documentation, and manufacturing continuity for all Linear ICs including the LTC3785 series.
The LTC3785 belongs to Linear's high-efficiency DC/DC controller family designed specifically for portable and battery-powered applications where input voltage varies widely relative to output - emphasizing low IQ, flexible topology, and robust protection.
FAQ
What is the operating temperature range for the LTC3785IUF#TRPBF?
The LTC3785IUF#TRPBF is specified for operation from −40°C to +125°C junction temperature. This industrial-grade rating ensures reliable performance in demanding environments such as automotive cabin modules, industrial handhelds, and outdoor wireless infrastructure - unlike the commercial-grade LTC3785EUF variants limited to −40°C to +85°C.
How does the LTC3785IUF#TRPBF achieve "No RSENSE" current limiting?
The LTC3785IUF#TRPBF senses forward current by measuring the voltage drop across the RDS(ON) of the external N-channel MOSFET A (between ISVIN and ISSW1), and reverse current across MOSFET D (between ISVOUT and ISSW2). This eliminates the need for discrete sense resistors, reducing power loss, board area, and BOM cost - a defining feature of the LTC3785IUF#TRPBF architecture.
Can the LTC3785IUF#TRPBF regulate output voltage when input equals output?
Yes - the LTC3785IUF#TRPBF operates seamlessly in buck-boost transition mode where VIN ≈ VOUT. Its four-switch topology and voltage-mode control allow continuous regulation across the full 2.7V–10V range without dropout or mode-hopping artifacts, making the LTC3785IUF#TRPBF ideal for battery-powered systems where input voltage crosses the output setpoint during discharge.
What is the purpose of the CCM pin on the LTC3785IUF#TRPBF?
The CCM pin on the LTC3785IUF#TRPBF selects reverse current limiting behavior: when pulled low, it enables a −15mV reverse threshold for minimal reverse conduction; when driven high, it sets symmetric forward/reverse limits based on ILSET. This allows designers to choose between ideal-diode operation (CCM low) or bidirectional current capability (CCM high) - a key flexibility unique to the LTC3785IUF#TRPBF.
Does the LTC3785IUF#TRPBF support output disconnect during shutdown?
Yes - the LTC3785IUF#TRPBF provides true output disconnect by fully disabling all four power switches during shutdown (RUN/SS < 0.35V). This prevents backfeed from VOUT to VIN, protecting upstream battery or supply sources - a critical safety and reliability feature absent in many competing controllers and explicitly confirmed in the LTC3785IUF#TRPBF datasheet.
LTC3785IUF#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 24-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Up/Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck-Boost
- Number of Outputs:
- 2
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 2.7V ~ 10V
- Frequency - Switching:
- 100kHz ~ 1MHz
- Duty Cycle (Max):
- 99%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Current Limit, Enable, Soft Start
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-QFN (4x4)
LTC3785IUF#TRPBF FAQ
1.How can I place an order for LTC3785IUF#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3785IUF#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 LTC3785IUF#TRPBF reliable?
The price and inventory of LTC3785IUF#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3785IUF#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3785IUF#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3785IUF#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3785IUF#TRPBF?
LTC3785IUF#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3785IUF#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 LTC3785IUF#TRPBF?
For technical support, including LTC3785IUF#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3785IUF#TRPBF requirements.
6.How does Aetrix verify that LTC3785IUF#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3785IUF#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 LTC3785IUF#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3785IUF#TRPBF?
All LTC3785IUF#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3785IUF#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 LTC3785IUF#TRPBF part is unused and in its original packaging.
Return procedure for LTC3785IUF#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LTC3785IUF#TRPBF Tags
-
UCC28C45DR
Texas Instruments
-
UCC28C40DR
Texas Instruments
-
UCC28C43DR
Texas Instruments
-
ZXSC410E6TA
Diodes Incorporated
-
LM3524DMX/NOPB
Texas Instruments
-
LM3489MMX/NOPB
Texas Instruments
-
MIC2102YML-TR
Microchip Technology
-
LM5148RGYR
Texas Instruments
-
TL598CDR
Texas Instruments
-
LM5155DSSR
Texas Instruments
-
LM25085MYX/NOPB
Texas Instruments
-
UCC2813DTR-0
Texas Instruments
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
