MAXIM Introduces New 4-String, HB LED Driver
Recently, Maxim introduced the highly integrated 4-string HB (high-brightness) LED driver MAX16814, which can output up to 150mA per channel. The device integrates all the features needed to build high-performance backlight drivers in LCDTVs, monitors and automotive displays. With this integrated architecture, the MAX16814 provides designers with a cost-effective solution that simplifies lighting design while maintaining high performance.
The MAX16814 integrates a switching DC-DC controller to generate the voltage required to drive multiple strings of LEDs. The device also features four linear current sinking circuits with on-chip power MOSFETs that provide up to 150mA of programmable current per string of LEDs. The adaptive output voltage control architecture optimizes efficiency and greatly reduces the power dissipation of the LED current sink. This architecture eliminates multiple external components and simplifies the design of space-constrained applications, saving space.
The MAX16814 is ideal for LCDTVs, desktop monitors, automotive displays and instruments, instrument clusters, and industrial display backlights. The device is also ideal for automotive headlights and near/high beam applications, as well as other SSL (solid state lighting) applications.
New requirements and new challenges for LCD display backlighting
HB LEDs are rapidly replacing CCFLs for backlighting LCDTVs, desktop monitors and automotive displays. The main driving force behind this shift is that HBLEDs have lower energy consumption, smaller form factor and higher reliability than CCFLs, and HB LEDs do not contain harmful chemicals (eg mercury).
Most applications use multiple LED strings and need to minimize cost. Multi-string drivers provide an excellent solution for this type of demand, increasing integration while reducing costs. However, there are many design challenges associated with efficiency, power consumption, dimming capability, fault protection, and EMI (electromagnetic interference).
Optimize efficiency and reduce power consumption while simplifying design
The multi-string driver consists of a switching converter and a multi-line current sinking circuit. To optimize efficiency, the output voltage of the switching converter must be set to the power supply | regulator voltage required for each string of LEDs. Optimizing the output voltage is critical for high-temperature applications such as automotive, where power consumption must be reduced to keep the circuit temperature within acceptable limits.
Traditional drivers require complex external circuitry to set the output voltage, and the MAX16814 integrates this functionality into the chip. The device's adaptive output voltage control architecture automatically detects the voltage required by the HBLED, which reduces power consumption. This architecture has a high degree of integration, which greatly reduces the cost of the solution.
Extend PWM dimming range to suit various ambient brightness conditions
The system requires a wide dimming range when working with constant ambient brightness. Such applications must be able to adapt to changes in brightness from intense daylight to complete darkness to ensure excellent visibility throughout the day. This feature is especially important for life-critical applications such as automotive, industrial and medical systems.
The PWM duty cycle of most multi-string drivers cannot be lower than a certain minimum value in order to properly set the output voltage of the switching converter. Therefore, the maximum dimming range for these drives is typically limited to 100:1.
The MAX16814 uses a unique technology (patent pending) that achieves an ultra-wide PWM dimming range of 5000:1 with a dimming frequency of 200Hz, which optimizes display performance in all brightness environments.
Ensuring the reliability of relational life safety applications
Life-critical applications require extreme reliability and fault tolerance. If an LED fails, it will suddenly short or open. In both cases, the HBLED driver circuit must be able to protect itself and the surrounding electrical system, issue a fault status warning signal to the electrical system, and minimize the impact of the fault on the user.
The MAX16814 features open and short fault protection. When an LED short circuit or open circuit occurs, the drive detects the fault and automatically turns off the affected LED string while keeping the other strings working properly. This type of protection greatly reduces the effects of the failure and prevents further damage to the system. In the above two fault situations, the fault status alarm signal can be sent to the rest of the system through an output pin.
In addition, the MAX16814 features overtemperature protection to prevent damage to the circuit in the event of overheating. These fail-safe circuits combine the high input voltage of the device with a wide operating temperature range to fundamentally ensure reliable operation of the device in harsh electrical and temperature environments.
Greatly reduced EMI
Electromagnetic compatibility is a challenge that many applications will encounter. For example, a common EMI challenge in automotive applications is to avoid electronic circuitry affecting AM broadcasts.
The MAX16814 allows the user to set the switching frequency from 200kHz to 2MHz, allowing the operating frequency to be higher than the AM broadcast band. In addition, when multiple MAX16814s are used in the same module, the oscillator synchronization function of the device can greatly reduce EMI noise. These features allow the device to reduce the number, size, and cost of components of the EMI filter in the system.
The most integrated solution on the market
In short, the MAX16814 offers the highest-performance, high-performance, multi-string HBLED driver solution on the market. The device not only integrates all current sink MOSFETs, it also greatly reduces the number of external components required for the design. The MAX16814 automates output voltage optimization, open and short-circuit LED protection, and wide-range PWM dimming without the need for external circuitry.
Designers can benefit from smaller solution sizes, lower BOM costs, and better system performance. In addition, fewer external components can reduce possible failure modes and increase system reliability.
Other advantages of HB LED drivers
For added flexibility, the switching regulator can be configured as a boost or SEPIC converter so that the voltage on the driven LED can be higher or lower than the input voltage. Other features include cycle-by-cycle current limit, output overvoltage protection, and overtemperature protection.
The MAX16814 operates over the -40°C to +125°C automotive temperature range, and its wide input voltage range (4.75V to 40V) allows it to withstand a 40V load dump. The device is available in a thermally enhanced 4mm x 4mm, 32-pin TQFN package and a 20-pin TSSOP package.
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The MAX16814 integrates a switching DC-DC controller to generate the voltage required to drive multiple strings of LEDs. The device also features four linear current sinking circuits with on-chip power MOSFETs that provide up to 150mA of programmable current per string of LEDs. The adaptive output voltage control architecture optimizes efficiency and greatly reduces the power dissipation of the LED current sink. This architecture eliminates multiple external components and simplifies the design of space-constrained applications, saving space.
The MAX16814 is ideal for LCDTVs, desktop monitors, automotive displays and instruments, instrument clusters, and industrial display backlights. The device is also ideal for automotive headlights and near/high beam applications, as well as other SSL (solid state lighting) applications.
New requirements and new challenges for LCD display backlighting
HB LEDs are rapidly replacing CCFLs for backlighting LCDTVs, desktop monitors and automotive displays. The main driving force behind this shift is that HBLEDs have lower energy consumption, smaller form factor and higher reliability than CCFLs, and HB LEDs do not contain harmful chemicals (eg mercury).
Most applications use multiple LED strings and need to minimize cost. Multi-string drivers provide an excellent solution for this type of demand, increasing integration while reducing costs. However, there are many design challenges associated with efficiency, power consumption, dimming capability, fault protection, and EMI (electromagnetic interference).
Optimize efficiency and reduce power consumption while simplifying design
The multi-string driver consists of a switching converter and a multi-line current sinking circuit. To optimize efficiency, the output voltage of the switching converter must be set to the power supply | regulator voltage required for each string of LEDs. Optimizing the output voltage is critical for high-temperature applications such as automotive, where power consumption must be reduced to keep the circuit temperature within acceptable limits.
Traditional drivers require complex external circuitry to set the output voltage, and the MAX16814 integrates this functionality into the chip. The device's adaptive output voltage control architecture automatically detects the voltage required by the HBLED, which reduces power consumption. This architecture has a high degree of integration, which greatly reduces the cost of the solution.
Extend PWM dimming range to suit various ambient brightness conditions
The system requires a wide dimming range when working with constant ambient brightness. Such applications must be able to adapt to changes in brightness from intense daylight to complete darkness to ensure excellent visibility throughout the day. This feature is especially important for life-critical applications such as automotive, industrial and medical systems.
The PWM duty cycle of most multi-string drivers cannot be lower than a certain minimum value in order to properly set the output voltage of the switching converter. Therefore, the maximum dimming range for these drives is typically limited to 100:1.
The MAX16814 uses a unique technology (patent pending) that achieves an ultra-wide PWM dimming range of 5000:1 with a dimming frequency of 200Hz, which optimizes display performance in all brightness environments.
Ensuring the reliability of relational life safety applications
Life-critical applications require extreme reliability and fault tolerance. If an LED fails, it will suddenly short or open. In both cases, the HBLED driver circuit must be able to protect itself and the surrounding electrical system, issue a fault status warning signal to the electrical system, and minimize the impact of the fault on the user.
The MAX16814 features open and short fault protection. When an LED short circuit or open circuit occurs, the drive detects the fault and automatically turns off the affected LED string while keeping the other strings working properly. This type of protection greatly reduces the effects of the failure and prevents further damage to the system. In the above two fault situations, the fault status alarm signal can be sent to the rest of the system through an output pin.
In addition, the MAX16814 features overtemperature protection to prevent damage to the circuit in the event of overheating. These fail-safe circuits combine the high input voltage of the device with a wide operating temperature range to fundamentally ensure reliable operation of the device in harsh electrical and temperature environments.
Greatly reduced EMI
Electromagnetic compatibility is a challenge that many applications will encounter. For example, a common EMI challenge in automotive applications is to avoid electronic circuitry affecting AM broadcasts.
The MAX16814 allows the user to set the switching frequency from 200kHz to 2MHz, allowing the operating frequency to be higher than the AM broadcast band. In addition, when multiple MAX16814s are used in the same module, the oscillator synchronization function of the device can greatly reduce EMI noise. These features allow the device to reduce the number, size, and cost of components of the EMI filter in the system.
The most integrated solution on the market
In short, the MAX16814 offers the highest-performance, high-performance, multi-string HBLED driver solution on the market. The device not only integrates all current sink MOSFETs, it also greatly reduces the number of external components required for the design. The MAX16814 automates output voltage optimization, open and short-circuit LED protection, and wide-range PWM dimming without the need for external circuitry.
Designers can benefit from smaller solution sizes, lower BOM costs, and better system performance. In addition, fewer external components can reduce possible failure modes and increase system reliability.
Other advantages of HB LED drivers
For added flexibility, the switching regulator can be configured as a boost or SEPIC converter so that the voltage on the driven LED can be higher or lower than the input voltage. Other features include cycle-by-cycle current limit, output overvoltage protection, and overtemperature protection.
The MAX16814 operates over the -40°C to +125°C automotive temperature range, and its wide input voltage range (4.75V to 40V) allows it to withstand a 40V load dump. The device is available in a thermally enhanced 4mm x 4mm, 32-pin TQFN package and a 20-pin TSSOP package.
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