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Analog Devices Inc. LT1768CGN#PBF
- Part No.:
- LT1768CGN#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Lighting, Ballast Controllers
- Package:
- 16-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LT1768CGN#PBF.pdf
- Description:
- IC CCFL CNTRL 410KHZ 16SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,509
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Product details
Overview
LT1768CGN#PBF from Analog Devices (formerly Linear Technology) is a high-power current-mode PWM controller IC designed specifically for driving cold cathode fluorescent lamps (CCFLs) in multi-lamp LCD backlight systems. It integrates a 1.5A MOSFET gate driver, 350kHz oscillator, 5V reference, and 100mV current-sense threshold, operating from 8V–24V input to enable wide-dimming-range, flicker-free illumination in desktop flat-panel and notebook displays.
For engineers reviewing the LT1768CGN#PBF datasheet, LT1768CGN#PBF pinout, LT1768CGN#PBF application, or LT1768CGN#PBF equivalent, key selection criteria include multimode dimming control (linear + PWM), open-lamp fault detection, programmable lamp current limits via RMIN/RMAX pins, thermal shutdown at 160°C, and SSOP-16 package compatibility with high-voltage CCFL transformer interfaces.
Technical Context
The LT1768CGN#PBF implements a current-mode PWM architecture where lamp current is regulated by comparing sensed switch current (via SENSE pin) against a dynamically controlled VC pin voltage derived from PROG/PWM inputs. Its multimode dimming scheme eliminates traditional error amplifiers, using a single-pole loop compensation network on the VC pin for fast transient response and minimal overshoot during startup or load changes.
Lamp current control spans five distinct modes-Off, Minimum, Linear, PWM, and Maximum-determined by PROG voltage (0.45V–4.2V), PWM pin voltage (1.75V–4V), and externally set RMIN/RMAX currents. DIO1/DIO2 pins provide bidirectional lamp current sensing and open-lamp detection via 125µA threshold, while FAULT pin signals fault conditions with open-collector output.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 8V to 24V - supports standard industrial DC rails and enables direct use with 12V/24V power supplies without pre-regulation. |
| Switching Frequency | 350kHz (typ) - sets core switching speed for high-efficiency, low-size magnetics in Royer-class CCFL inverters. |
| Gate Drive Current | ±1.5A peak - directly drives external N-channel MOSFETs with low gate charge, eliminating need for buffer stages. |
| Current Sense Threshold | 100mV (typ) - enables precise, low-loss current sensing with small-value sense resistors (e.g., 0.025Ω). |
| Reference Voltage | 5.0V ±1% - stable, load-regulated output powers external bias circuitry or ADC references without additional regulators. |
| Shutdown Supply Current | 65µA (typ) - ensures ultra-low standby power in display sleep modes while retaining fast wake-up capability. |
| Operating Temperature | 0°C to 125°C (junction) - qualified for commercial-grade embedded display applications with thermal margin for enclosed enclosures. |
Pinout & Package
The LT1768CGN#PBF is housed in a 16-lead plastic SSOP (Shrink Small Outline Package) with 0.65mm lead pitch, optimized for high-voltage isolation and thermal dissipation in CCFL inverter PCB layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| PGND (1) | Power Ground | High-current return path for MOSFET switching and lamp current; must be routed separately from AGND to avoid noise coupling. |
| DIO1/DIO2 (2,3) | Lamp Current Interface | Bidirectional terminals for CCFL cathode/anode return; internally route half-wave rectified lamp current to VC pin for closed-loop regulation and open-lamp detection. |
| SENSE (4) | Current Sense Input | Connects to shunt resistor on MOSFET source; comparator triggers switch turn-off when voltage exceeds VC-derived threshold (85–115mV). |
| VC (5) | Control Summing Junction | Sum point for PROG/PWM programming current and lamp feedback; capacitor here provides single-pole loop compensation and current averaging. |
| AGND (6) | Analog Ground | Low-noise reference for VREF, RMIN, RMAX, and internal comparators; requires star connection to minimize offset errors. |
| CT (7) | PWM Frequency Set | Capacitor value (e.g., 0.22µF) sets PWM modulation frequency per f = 22Hz/CT(µF), also defining lamp fault timeout window. |
| PROG (8) | Dimming Control Input | 0–5V analog or 1kHz PWM input that maps to VC source current across five operational modes (Off to Max Current). |
| PWM (9) | Modulation Range Select | Voltage (1.75–4V) defines percentage of PROG range subject to PWM dimming; sets duty cycle via [1 – (VPWM–VPROG)/(VPWM–1V)] × 100%. |
| RMAX (10) | Max Lamp Current Set | 1.25V regulated output loaded with external resistor; IRMAX × 100 ≈ max dual-lamp current (e.g., 9mA with 16.2kΩ). |
| RMIN (11) | Min Lamp Current Set | 1.26V regulated output loaded with external resistor; IRMIN × 10 ≈ min dual-lamp current; connect to VREF for zero-minimum dimming. |
| SHDN (12) | Enable/Shutdown Control | Logic-high (>1.26V) enables operation; logic-low (<1V) reduces supply current to 65µA and disables GATE, VREF, and oscillation. |
| FAULT (13) | Fault Indicator Output | Open-collector sink (1mA) activated when DIO1 or DIO2 current <125µA for ≥1 PWM period; pulls low to signal lamp failure or short. |
| VREF (14) | 5V Reference Output | Stable 5V supply (±1%, 10mA capable) derived from VIN; disabled during UVLO, shutdown, or thermal shutdown. |
| VIN (15) | Main Power Input | 8–24V supply with 7.9V UVLO turn-on; absolute max 28V; powers all internal circuits except gate driver high-side clamp. |
| GATE (16) | MOSFET Driver Output | NPN output stage with ±1.5A drive; clamped to ~12.5V above 13V VIN; minimum on-time 125ns; max duty 93% at 350kHz. |
Key Features
| Feature | Design Value |
|---|---|
| Ultrawide Multimode Dimming™ | Combines linear and PWM control across 0–5V PROG input to achieve >100:1 dimming ratio without lamp flicker or lifetime degradation. |
| Programmable Lamp Current Limits | RMIN and RMAX pins allow independent setting of min/max lamp current (e.g., 0–9mA) to match CCFL manufacturer specifications and maximize lifetime. |
| Open Lamp Detection | DIO1/DIO2 monitor lamp current continuously; FAULT pin asserts if either pin sees <125µA for ≥1 PWM cycle, enabling fail-safe display shutdown. |
| Integrated 5V Reference | VREF pin delivers ±1% 5V at up to 10mA, eliminating need for external reference ICs in bias networks or ADC interfaces. |
| Thermal Shutdown Protection | Internal sensor disables GATE and oscillation at 160°C junction temperature, preventing damage during overload or poor heatsinking. |
Applications
| Desktop Flat Panel Displays | Multiple Lamp Displays |
|---|---|
Use Scenario: 19–24-inch LCD monitors requiring uniform backlighting across dual or quad CCFL arrays with smooth brightness control. IC Role / Device Role / Timing Role: Primary CCFL controller managing GATE-driven MOSFET, lamp current regulation via DIO1/DIO2 feedback, and multimode dimming via PROG/PWM inputs. Use Value: Enables 100:1 dimming ratio while maintaining lamp current within manufacturer-specified min/max limits, extending display lifetime beyond 50,000 hours. | Use Scenario: Industrial kiosks or medical displays using three or more CCFLs per side to ensure edge-to-edge brightness uniformity. IC Role / Device Role / Timing Role: High-current PWM controller coordinating multiple lamps through shared CT timing and independent RMIN/RMAX current programming. Use Value: Eliminates need for multiple controllers; single LT1768CGN#PBF supports up to four lamps with synchronized dimming and fault reporting. |
| Notebook LCD Displays | Point of Sale Terminal Displays |
Use Scenario: 13–15.6-inch laptop screens where space, efficiency, and EMI are critical constraints. IC Role / Device Role / Timing Role: Compact CCFL driver implementing sinusoidal lamp drive via Royer converter (T1/C4/Q1), minimizing RF emissions and migration effects. Use Value: Achieves >90% inverter efficiency and zero-DC lamp current, reducing heat generation and extending battery runtime during display use. | Use Scenario: Retail POS terminals with always-on displays requiring reliable, long-life backlighting under ambient temperature variations. IC Role / Device Role / Timing Role: Fault-tolerant CCFL controller with open-lamp detection and thermal shutdown, ensuring continuous operation even with partial lamp failure. Use Value: Prevents complete display blackout on single-lamp failure; FAULT pin alerts system MCU to initiate graceful degradation or service alert. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar CCFL controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX8722AEEE+ | Fixed 200kHz switching frequency; no programmable RMIN/RMAX; uses external op-amp for current sense. | Limited to single-lamp designs; lacks multimode dimming and open-lamp detection; lower integration. | Choose MAX8722AEEE+ only for cost-sensitive, single-lamp applications where dimming range <30:1 is acceptable. |
| LM3481MM/NOPB | General-purpose current-mode PWM controller; no integrated CCFL-specific features (DIO1/DIO2, FAULT, RMIN/RMAX). | Requires full custom design for CCFL drive including lamp sensing, fault logic, and dimming interface; no native open-lamp protection. | Select LM3481MM/NOPB only when designing non-standard topologies or when leveraging existing buck/boost controller expertise and layout resources. |
Compared with MAX8722AEEE+ and LM3481MM/NOPB, the LT1768CGN#PBF delivers superior integration for CCFL backlighting-reducing BOM count by 40%, enabling >100:1 flicker-free dimming, and providing built-in fault diagnostics that eliminate external monitoring circuitry.
Availability
LT1768CGN#PBF is available at Aetrix Electronics and suitable for desktop flat panel displays, notebook LCD displays, and point-of-sale terminal displays requiring stable component supply, long-term lifecycle support, and guaranteed traceability for industrial OEM programs.
Supply support for LT1768CGN#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, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed through the acquisition of Linear Technology in 2017.
The LT1768CGN#PBF belongs to ADI's legacy Linear Technology CCFL controller product line, engineered specifically for high-reliability, wide-dimming-range LCD backlighting in commercial and industrial display systems.
FAQ
What is the primary function of the LT1768CGN#PBF in an LCD backlight system?
The LT1768CGN#PBF serves as a dedicated high-power CCFL controller IC that regulates lamp current using current-mode PWM, implements multimode dimming (linear + PWM), detects open-lamp faults via DIO1/DIO2, and drives an external MOSFET through its 1.5A GATE output. In every LT1768CGN#PBF-based design, it replaces discrete control logic and ensures compliance with CCFL manufacturer current specifications to maximize lamp lifetime.
How does the LT1768CGN#PBF achieve flicker-free dimming across a wide range?
The LT1768CGN#PBF achieves flicker-free dimming by combining linear control (for low-current stability) and PWM modulation (for extended range) within its patented Multimode Dimming™ architecture. It avoids low-frequency PWM artifacts by using a high 350kHz switching frequency and synchronizing lamp current regulation to the VC pin's single-pole loop, ensuring smooth transitions across the full 0–5V PROG input range. This behavior is intrinsic to the LT1768CGN#PBF and validated in typical application circuits like Figure 1.
Can the LT1768CGN#PBF drive more than two CCFL lamps?
Yes, the LT1768CGN#PBF can drive up to four CCFL lamps using a shared Royer-class inverter topology, as confirmed by its "Multiple Lamp Capability" feature and dual DIO1/DIO2 current-sensing inputs. Each lamp connects to one DIO pin, and the LT1768CGN#PBF independently monitors both paths for open-circuit faults. The RMIN and RMAX resistors scale total current proportionally-e.g., 10×IRMIN sets minimum current per lamp in dual-lamp mode, and 100×IRMAX sets maximum per lamp in quad-lamp configurations.
What happens when the FAULT pin activates on the LT1768CGN#PBF?
When the FAULT pin activates on the LT1768CGN#PBF, it sinks up to 1mA as an open-collector signal indicating lamp failure-triggered when DIO1 or DIO2 current falls below 125µA for at least one full PWM cycle. Upon activation, the LT1768CGN#PBF reduces maximum allowable lamp current by ~50%; if both DIO pins fault simultaneously and VC clamps at 3.7V, the GATE driver latches off. Clearing requires pulling PROG to 0V or asserting SHDN.
Is the LT1768CGN#PBF compatible with 5V-only microcontroller dimming interfaces?
Yes, the LT1768CGN#PBF accepts 0–5V DC or 1kHz PWM signals on its PROG pin, making it fully compatible with standard 5V microcontrollers. Its PROG input bias current is only 100–500nA, imposing negligible load on MCU GPIOs. For PWM dimming, the LT1768CGN#PBF interprets the duty cycle and voltage level jointly with the PWM pin to determine modulation range-no level-shifting or external conditioning is required for direct 5V MCU interfacing.
LT1768CGN#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-SSOP (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- CCFL Controller
- Frequency:
- 300kHz ~ 410kHz
- Voltage - Supply:
- 8V ~ 24V
- Current - Supply:
- 7 mA
- Current - Output Source/Sink:
- -
- Dimming:
- Yes
- Operating Temperature:
- 0°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SSOP
LT1768CGN#PBF FAQ
1.How can I place an order for LT1768CGN#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1768CGN#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 LT1768CGN#PBF reliable?
The price and inventory of LT1768CGN#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1768CGN#PBF is usually 5 days.
3.What payment methods are accepted for LT1768CGN#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1768CGN#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1768CGN#PBF?
LT1768CGN#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1768CGN#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 LT1768CGN#PBF?
For technical support, including LT1768CGN#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1768CGN#PBF requirements.
6.How does Aetrix verify that LT1768CGN#PBF is sourced from the original manufacturer or authorized distributors?
All LT1768CGN#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 LT1768CGN#PBF meets industry standards.
7.What is the process for return or replacement of LT1768CGN#PBF?
All LT1768CGN#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1768CGN#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 LT1768CGN#PBF part is unused and in its original packaging.
Return procedure for LT1768CGN#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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