Demonstration circuit DC2857A is a 36V 2A synchronous 2MHz boost LED driver featuring the LT3922-1. It drives a single string of LEDs at 330mA up to 34V when VIN is between 7V and 28V. It runs down to 4VIN with reduced ILED and can withstand VIN as high as 36V, but has overvoltage lockout (OVLO) set for 28V for this application. DC2857A runs at 2MHz switching frequency. Spread spectrum frequency modulation (SSFM) can be turned on with a simple jumper, reducing EMI. DC2857A comes with low EMI features including optimized layout, SSFM and input EMI filter. It passes CISPR 25 class 5 conducted and radiated EMI. It is protected against both open and short LED conditions and reports the faults. The LT3922-1 has an input voltage range from 2.8V to 36V. Its internal synchronous 2A 40V switches allow up to 34V of LEDs on the output with room for over voltage protection and overshoot during an open LED event. It has adjustable switching frequency between 200kHz and 2.5MHz. It can be synchronized to an external source or programmed with SSFM for low EMI. The PWMTG highside PWM MOSFET driver assists with short-circuit protection and versatility. LT3922-1 can be configured as a boost, boost-buck, or buck mode LED driver and maintain all of its low EMI, PWM dimming, and fault diagnostic features. The LT3922-1 can be PWM dimmed with an external PWM signal or an internally-generated PWM signal. DC2857A has a jumper that can be set to switch between internallygenerated PWM signal, externally-generated PWM signal, and no PWM signal (100% on). It can be analog dimmed with a control voltage on its control pin (CTRL). When run with both PWM dimming and spread spectrum, the spread spectrum aligns itself with the PWM signal for flicker-free operation. Small ceramic input and output capacitors are used to save space and cost. The board is designed with tiny, high frequency capacitors on both sides of the VOUT pins for a reduction in radiated EMI. The open LED overvoltage protection uses the IC’s constant voltage regulation loop to regulate the output to approximately 37.5V if the LED string is opened, although it may reach almost 40V peak during transient from running LEDs to open. There is a protection diode from LED+ to GND to prevent negative ringing during a short-circuit. The output current can be monitored through the ISMON output pin. Undervoltage and overvoltage lockout can be adjusted on the circuit with a few simple resistor choices. There is an EMI filter on the input of DC2857A. Please follow the recommend layout and four-layer thickness of DC2857A for low EMI applications. The LT3922-1 data sheet gives a complete description of the part, operation and applications information. The LT3922EUFD-1 is assembled in a 28-lead plastic 4mm × 5mm QFN package with a thermally enhanced ground pad. Proper board layout is essential for maximum thermal performance. See the data sheet section Layout Considerations.

applications such as automotive TFT LCD backlights, courtesy lighting and heads-up displays. One of

temperature range of ?40?C to +125?C.APPLICATIONS Portable electronics level adjustment LCD panel

for LCD back-light or contrast control. The AD7877 runs in either slave or master mode using a

DC336A - Demo Board

Evaluation board EVAL-LT8376-AZ is a 60V, 2A synchronous Buck LED driver featuring the LT8376. EVAL-LT8376-AZ drives a single string of LEDs up to 36V at 1.5A when VIN is between 43V and 57V. EVAL-LT8376-AZ has an undervoltage lockout (UVLO) set at 40V with 2V hysteresis for turn-on. EVAL-LT8376-AZ runs at 350kHz switching frequency and features optional spread spectrum modulation (SSFM). With SSFM enabled, LT8376 modulates its switching frequency from fSW to fSW + 25% to reduce EMI emissions. The LT8376 has an input voltage range of 3.6V to 60V. LT8376 has internal, synchronous 60V switches for high efficiency and small size. LT8376 has an adjustable switching frequency between 200kHz and 2MHz. The LT8376 can be synchronized with an external clock source or configured with SSFM enabled for low EMI. EVAL-LT8376-AZ includes a SYNC/SSFM jumper to configure the LT8376 for either external frequency synchronization, SSFM enabled for low EMI, or set to normal operation with SSFM disabled. The LT8376’s integrated PWMTG high-side PMOS driver assists with PWM dimming of the connected LEDs. The LED string can be PWM dimmed for accurate brightness control with an externally generated PWM signal or an internally-generated PWM signal. EVAL-LT8376-AZ has jumpers that can be set to switch between internally-generated PWM signal, externally generated PWM signal, and 100% on with no PWM signal. The LT8376 can also be analog dimmed by placing a controllable DC voltage on the CTRL pin. When running PWM dimming with SSFM enabled, the SSFM aligns itself with the PWM signal for flicker-free operation of the LED string. This applies to both internal and external PWM dimming. Small ceramic input and output capacitors are used to save space and cost. The input and output filters on EVAL-LT8376-AZ reduce its EMI. The filters consist of a small ferrite bead or inductor and high frequency ceramic capacitors. These filters, combined with proper board layout and SSFM, are very effective in reducing EMI to comply with CISPR25 class 5 limits. Please follow the recommended layout and the four-layer PCB thickness of EVAL-LT8376-AZ. For best efficiency and PWM dimming performance, the EMI filters at the input and output can be removed. The open LED overvoltage protection (OVP) uses the IC’s constant voltage regulation loop to regulate the output to approximately 41V if the LED string is opened. The output current can be monitored through the ISMON pin. Also, the FAULT pin can be used for open and short detection. The input undervoltage lockout (UVLO), LED current, output overvoltage protection (OVP), and switching frequency, can all be easy adjusted with simple modifications to EVAL-LT8376-AZ. The LT8376 data sheet gives a complete description of the device, operation, and applications information. The data sheet must be read in conjunction with this demo manual for evaluation board EVAL-LT8376-AZ. The LT8376RV is assembled in a 28-lead plastic LQFN package with a thermally enhanced exposed ground pad. Proper board layout is essential for maximum performance. See the data sheet section “Designing the Printed Circuit Board”.

DC805A: Demo Board for the LTC3216 1A Low Noise High Current LED Charge Pump with Independent Torch/Flash Current Control.

soft start is implemented to reduce inrush current during startup. Applications LCD monitor and TV LED backlights Industrial lighting

(LFCSP).APPLICATIONS TFT LCD bias supplies Portable applications Industrial/instrumentation equipment

applications such as automotive TFT LCD backlights, courtesy lighting and heads-up displays. One of