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MAX16834EVKIT 数据表(PDF) 4 Page - Maxim Integrated Products |
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MAX16834EVKIT 数据表(HTML) 4 Page - Maxim Integrated Products |
4 / 10 page LED Dimming Operation Jumper JU1 configures the MAX16834 EV kit for analog linear dimming or PWM dimming control of the external LEDs. Install a shunt across jumper JU1 to control the LED brightness using a linear voltage applied at the MAX16834 REFI pin. Remove the shunt at jumper JU1 to control the LED brightness using a PWM signal applied at the PWMDIM and SGND PCB pads. See Table 1 for jumper JU1 settings for LED dimming operation. Linear Dimming Control The MAX16834 EV kit offers analog linear dimming of the external LEDs connected between the LED+ and LED- PCB pads. Resistor R5 and potentiometer R17 set the external LEDs’ maximum average current to 1A by adjusting the voltage at the MAX16834 REFI input. Vary the MAX16834’s REFI voltage using potentiometer R17 to adjust the LEDs’ brightness. LED brightness increas- es when the voltage at REFI is increased and vice versa. The MAX16834 REFI pin voltage can be moni- tored by placing a voltmeter across the REFI and SGND PCB pads. The LED string dimming current can be adjusted using the following equation: VREFI = 9.9 × ILED × R5 where VREFI is the voltage at the REFI PCB pad, ILED is the LED current in amperes, and R5 is the sense resistor, in ohms, connected between N1’s source and the MAX16834 LV pin. Digital PWM Dimming Operation LED dimming can be achieved on the MAX16834 EV kit by applying a digital PWM signal at the EV kit’s PWMDIM and SGND PCB pads. Connect a PWM signal with a 1.5V to 5V logic-high level and frequencies from DC to 20kHz. Vary the PWM signal duty cycle to adjust the LEDs’ brightness. Fault Indicator (FLT) The MAX16834EV kit features an output pad (FLT) to monitor the FLT output logic signal. FLT is low when any of the following conditions occur: • Open-circuit condition across the LED+ and LED- PCB pads • Short-circuit condition across the LED+ and LED- PCB pads • MAX16834 IC overtemperature fault condition When the LED+ voltage drops below the programmed overvoltage set point minus the MAX16834 hysteresis, FLT deasserts. During a short-circuit condition, FLT deasserts when dimming MOSFET N1 is on. The FLT signal is the inverse of the PWMDIM signal during an overtemperature fault condition (TJ > 140°C). Output Overvoltage Protection The maximum voltage on the LED+ pin is limited to 34.7V with respect to LV by a feedback network formed by resistors R11 and R12. When the LED+ to LV voltage difference exceeds the programmed 34.7V threshold, PWM switching is terminated, FLT asserts low, and no further energy is transferred to the load connected between the LED+ and LED- PCB pads. Refer to the Setting the Overvoltage Threshold section in the MAX16834 IC data sheet for setting the overvolt- age threshold. Optional Automotive Load Dump Protection (Boost Mode Only) The MAX16834 EV kit provides PCB component foot- prints for an optional load dump protection circuit (C19, D5, Q1, and R21). This limits the MAX16834 IN pin volt- age below its absolute maximum 30V rating when oper- ating the EV kit circuit in boost-mode operation under load dump conditions. When configuring the MAX16834 EV kit for load dump operation, remove resistor R3. NPN transistor Q1 should have a 75V/100mA (min) rating. Zener diode D5 should have a 24V/100mA rating. Reconfiguring the MAX16834 EV Kit for Buck-Boost Operation The MAX16834 EV kit can be reconfigured for buck- boost operation by removing and adding the following components: • Remove resistors R4 and R8. • Install a 0 Ω resistor at R3. • Install components at D1 (6V zener) and R7 (2.7k Ω). MAX16834 Evaluation Kit 4 _______________________________________________________________________________________ Table 1. JU1 Jumper Selection SHUNT POSITION PWMDIM PIN EV KIT DIMMING OPERATION Installed Connects to R14/R20 network Linear dimming control Not installed Connects to external PWM signal PWM dimming control |
类似零件编号 - MAX16834EVKIT |
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类似说明 - MAX16834EVKIT |
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