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Analog Devices Inc. LT1786FCS#TRPBF
- Part No.:
- LT1786FCS#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Special Purpose Regulators
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1786FCS#TRPBF.pdf
- Description:
- IC REG CONV CCFL 1OUT 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,046
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Product details
Overview
LT1786FCS#TRPBF from Analog Devices (formerly Linear Technology) is a fixed-frequency, current-mode CCFL switching regulator IC designed for precision backlight control in portable LCD displays. It integrates a 6-bit 100µA full-scale DAC, SMBus interface, high-side current sense amplifier, and 1.25A NPN power switch. It supports grounded- or floating-lamp configurations and operates from 4.5V–30V battery input with 200kHz switching frequency.
For engineers reviewing the LT1786FCS#TRPBF datasheet, LT1786FCS#TRPBF pinout, LT1786FCS#TRPBF application, or LT1786FCS#TRPBF equivalent, key selection criteria include SMBus programmability of lamp current, open-lamp protection, shutdown modes (SHDN/SMBSUS), DAC retention in suspend, and compatibility with Royer converter topologies in space-constrained portable systems.
Technical Context
The LT1786FCS#TRPBF implements current-mode control using cycle-by-cycle peak-current limiting and internal slope compensation to ensure stability at duty cycles up to 85%. Its lamp-current programming block accepts 0–100µA DAC output (IOUT) and converts it to a 0–500µA source current at CCFL VC, enabling precise closed-loop regulation of lamp current via either DIO (grounded lamp) or BAT/ROYER (floating lamp) sensing paths.
It functions as an SMBus slave device with two selectable addresses (0x58 or 0x5A) set by ADR pin logic level, supporting write-byte commands for DAC setting and SHDN bit control. The 2.4V internal LDO powers analog circuitry, while quiescent current drops to 40µA in SMBSUS mode and 150µA in SHDN mode-retaining DAC state in both.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| DAC Resolution | 6-bit - provides 64 discrete lamp current steps for smooth brightness control without hysteresis. |
| DAC Full-Scale Current | 100µA ±4µA - sets maximum lamp current scale; directly programs CCFL VC reference for closed-loop regulation. |
| Switching Frequency | 200kHz typical - minimizes magnetic component size and enables compact Royer transformer design. |
| Max Switch Current | 1.25A at 50% duty cycle - supports high-brightness CCFLs; derates to 0.9A at 75% due to internal slope compensation. |
| Input Voltage Range (BAT) | 4.5V to 30V - accommodates wide battery chemistries (Li-ion, Li-Poly, multi-cell alkaline) without external regulators. |
| SMBus Interface | 2-wire, 10–100kHz - enables digital lamp current adjustment and status monitoring from host microcontroller without analog DAC or PWM circuitry. |
| Operating Temp Range | 0°C to 70°C ambient - validated for notebook, PDA, and portable instrument environments with thermal shutdown at 100°C junction. |
Pinout & Package
The LT1786FCS#TRPBF is housed in a 16-pin narrow SOIC package (SO-16N) with exposed pad not specified for thermal enhancement per datasheet. Pin functions are electrically validated and layout-critical for noise immunity and current-sense accuracy.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CCFL PGND (1) | Emiter of internal NPN power switch | Provides low-impedance return path for switch current; must be star-grounded separately from AGND to avoid coupling noise into analog sensing. |
| ICCFL (2) | DAC current summing node | Regulated at 0.465V; sinks 0–100µA DAC output (IOUT) to generate proportional lamp current command. |
| DIO (3) | Grounded-lamp current sense interface | Connects to low-side lamp terminal; alternately conducts half-wave lamp current to enable averaging and fast loop response. |
| CCFL VC (4) | Lamp current error amplifier output | High-impedance node setting switch turn-off threshold; capacitor here provides loop compensation and clamping adjusts current limit. |
| AGND (5) | Analog ground reference | Reference for 1.24V bandgap and ICCFL summing; must be isolated from power ground to preserve DAC and sensing accuracy. |
| SHDN (6) | Partial shutdown control | Active-low input disabling CCFL control circuitry only; DAC remains powered (150µA standby current). |
| SMBSUS (7) | Full suspend control | Active-low input disabling entire IC except SMBus interface; retains DAC setting (40µA standby current). |
| ADR (8) | SMBus address select | Logic level selects address 0x58 (VCC = mid-scale startup) or 0x5A (GND = zero-scale startup). |
| SDA (9) | SMBus bidirectional data | Open-drain I/O requiring pull-up; carries command/data bytes and ACK/NACK during communication. |
| SCL (10) | SMBus clock input | High-impedance input requiring pull-up; defines timing for data sampling and ACK generation. |
| IOUT (11) | DAC current output | 6-bit programmable 0–100µA sink; biased from –10V to (VCC – 1.3V); directly connected to ICCFL for lamp control. |
| VCC (12) | Logic supply input | 3.0V–6.5V tolerant; powers internal 2.4V LDO and digital logic; undervoltage lockout below ~2.5V. |
| ROYER (13) | Floating-lamp primary current sense | Inverting input of high-side current amplifier; used with BAT to sense Royer center-tap current in floating configuration. |
| BAT (14) | Battery input / high-side sense reference | 4.5V–30V input; supplies bias for lamp programming block and connects to open-lamp protection clamp (BAT–BULB). |
| BULB (15) | Open-lamp protection comparator input | Monitors voltage across Royer primary; triggers clamp when >7.0V to prevent transformer overvoltage during start-up or lamp failure. |
| CCFL VSW (16) | Power switch collector | Drives Royer transformer primary; rated 60V breakdown; requires external snubber for EMI suppression in high-dV/dt applications. |
Key Features
| Feature | Design Value |
|---|---|
| Two SMBus addresses | Selectable via ADR pin (0x58 or 0x5A), enabling multiple LT1786FCS#TRPBF devices on same bus without address conflict. |
| DAC state retention in suspend | SMBSUS mode preserves programmed IOUT value; eliminates re-initialization delay after wake-up in battery-powered systems. |
| Open-lamp protection | Integrated BAT–BULB comparator limits primary voltage to ≤7.5V, preventing transformer saturation and secondary overvoltage during lamp removal or failure. |
| Grounded/floating lamp support | Single IC supports both topologies: DIO-based sensing for grounded lamps; BAT/ROYER differential sensing for symmetric floating drive and reduced frame capacitance loss. |
| Current-mode switching with slope compensation | Ensures stable operation up to 85% duty cycle; eliminates need for external compensation components in most Royer designs. |
| Low-quiescent shutdown modes | SHDN = 150µA (DAC active), SMBSUS = 40µA (full suspend); critical for extending battery life in always-on display subsystems. |
Applications
| Backlit Notebook Displays | Portable Medical Instruments |
|---|---|
Use Scenario: 10–15 inch LCD panel in battery-operated laptop requiring adjustable brightness, low EMI, and reliable lamp ignition across temperature. IC Role / Device Role / Timing Role: CCFL switching regulator controlling lamp current via SMBus; provides constant-current drive with 200kHz switching and open-lamp fault detection. Use Value: Enables 0–100% dimming without pop-on/hysteresis, achieves >90% efficiency, and reduces PCB area vs. discrete solutions by integrating DAC, SMBus, and high-current switch. |
Use Scenario: Handheld ultrasound or patient monitor with high-contrast LCD needing flicker-free, medically certified backlight control. IC Role / Device Role / Timing Role: Precision lamp current controller with retained DAC state and thermal shutdown; ensures consistent luminance during intermittent use. Use Value: Maintains calibrated brightness across 0°C–70°C ambient; SMBus interface allows host MCU to log lamp health and trigger diagnostics on BULB comparator faults. |
| PDA & Industrial HMI Panels | Test & Measurement Equipment |
Use Scenario: Compact industrial HMI with sealed enclosure and 5mm height constraint requiring minimal external components. IC Role / Device Role / Timing Role: Integrated CCFL driver with Royer topology support; uses BAT/ROYER sensing for floating-lamp configuration to minimize stray capacitance losses. Use Value: Eliminates need for external current-sense resistors or op-amps; single capacitor on CCFL VC provides full loop compensation, reducing BOM count by ≥4 parts. |
Use Scenario: Benchtop oscilloscope or spectrum analyzer requiring stable, low-noise display illumination during long acquisitions. IC Role / Device Role / Timing Role: Low-noise CCFL regulator with separate AGND/PGND and star-ground layout guidance to prevent analog signal contamination. Use Value: Delivers <±0.1% lamp current ripple; thermal shutdown prevents drift during extended operation; SMBus allows remote brightness calibration via host PC software. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar CCFL regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1785FCS#TRPBF | Same pinout and SMBus interface, but lacks SMBSUS pin and DAC retention in suspend; 50µA lower standby current in SHDN mode. | Not suitable where firmware-initiated brightness restore after deep sleep is required; limited to simpler shutdown-only systems. | Select LT1786FCS#TRPBF when DAC state retention across suspend/resume cycles is mandatory for user experience continuity. |
| MAX8722AETI+ | 5V-only VCC supply (no 3.3V support); no integrated DAC; requires external 8-bit I²C DAC and current-sense resistor. | Higher BOM cost and layout complexity; supports higher switching frequencies (up to 1MHz) for ultra-compact magnetics. | Choose LT1786FCS#TRPBF for lowest component count and guaranteed SMBus interoperability in 3.3V/5V mixed-supply portable designs. |
Compared with LT1785FCS#TRPBF and MAX8722AETI+, the LT1786FCS#TRPBF uniquely combines SMBus-addressable DAC retention, dual shutdown modes, and Royer-compatible sensing in a single SO-16 package-reducing system-level validation effort and enabling faster time-to-market for battery-sensitive CCFL backlight designs.
Availability
LT1786FCS#TRPBF is available at Aetrix Electronics and suitable for notebook computers, portable medical instruments, industrial HMIs, and test equipment requiring stable component supply with full lifecycle support.
Supply support for LT1786FCS#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT1786FCS#TRPBF belongs to Linear's CCFL backlight regulator product line, engineered specifically for energy-efficient, digitally controllable LCD backlighting in space- and battery-constrained portable electronics.
FAQ
What is the function of the SMBSUS pin on the LT1786FCS#TRPBF?
The SMBSUS pin on the LT1786FCS#TRPBF enables full IC suspend mode: pulling it low reduces supply current to 40µA while retaining the DAC's last programmed IOUT value. This allows rapid brightness restoration upon wake-up without SMBus reinitialization. It can also be activated via SMBus command byte Bit 7 = 1, making LT1786FCS#TRPBF ideal for low-power portable systems with frequent sleep/wake cycles.
How does the LT1786FCS#TRPBF support both grounded-lamp and floating-lamp configurations?
The LT1786FCS#TRPBF supports grounded-lamp mode via DIO pin connection to the lamp's low side, enabling half-wave current sensing and averaging. For floating-lamp mode, DIO is grounded and lamp current is sensed differentially across BAT and ROYER pins-measuring Royer primary current directly. This dual-path architecture eliminates need for external sensing components and reduces parasitic losses in high-resolution displays.
What is the maximum lamp current achievable with the LT1786FCS#TRPBF?
The LT1786FCS#TRPBF does not directly specify maximum lamp current, as it depends on external Royer transformer turns ratio, switching frequency, and lamp impedance. However, its internal 1.25A switch (at 50% duty cycle) and 0–100µA DAC output translate to typical lamp currents of 0–6mA for standard CCFLs. Designers must verify lamp compliance using the CCFL VC clamp voltages (0.1V–2.4V) and BULB comparator thresholds (6.5V–7.5V) per application circuit.
Can the LT1786FCS#TRPBF operate from a 3.3V logic supply?
Yes, the LT1786FCS#TRPBF supports VCC from 3.0V to 6.5V, including standard 3.3V logic rails. Its internal 2.4V LDO maintains stable analog bias across this range, and SMBus timing (10–100kHz) is fully compliant at 3.3V. Quiescent current increases only marginally-from 6mA at 3.3V to 9.5mA at 6.5V-making LT1786FCS#TRPBF well-suited for mixed-voltage portable platforms.
What protection features are integrated into the LT1786FCS#TRPBF?
The LT1786FCS#TRPBF integrates open-lamp protection (via BAT–BULB comparator), thermal shutdown (100°C junction limit), undervoltage lockout (~2.5V), cycle-by-cycle current limiting, and anti-saturation drive for the internal switch. These features prevent damage during lamp removal, overtemperature, low-battery conditions, or Royer transformer saturation-eliminating need for external fault-handling circuitry in certified medical and industrial designs.
LT1786FCS#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Applications:
- Converter, CCFL
- Voltage - Input:
- 4.5V ~ 30V
- Number of Outputs:
- 1
- Voltage - Output:
- -
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SO
LT1786FCS#TRPBF FAQ
1.How can I place an order for LT1786FCS#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1786FCS#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 LT1786FCS#TRPBF reliable?
The price and inventory of LT1786FCS#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1786FCS#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1786FCS#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1786FCS#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1786FCS#TRPBF?
LT1786FCS#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1786FCS#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 LT1786FCS#TRPBF?
For technical support, including LT1786FCS#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1786FCS#TRPBF requirements.
6.How does Aetrix verify that LT1786FCS#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1786FCS#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 LT1786FCS#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1786FCS#TRPBF?
All LT1786FCS#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1786FCS#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 LT1786FCS#TRPBF part is unused and in its original packaging.
Return procedure for LT1786FCS#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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