Other Parts Discussed in Thread: LM3404, LM3404HV
TI customer service has referred me to this site after responding to several case studies. Basically we ne to control LED lighting with contrast ratio of around 25000 to 1. We are using the LM3402-04 application board. In the AN-1839 paper it says we can achieve higher than a 50000 to 1 contrast ratio. I have several questions that are in the following paragraph that I typed for the case study. All help you can give us is greatly appreciated.
Original details: Please see CS 0082366. My colleagues and I still need some spoon feeding. The LM3402-04App board does not match the schematic in your users guide SNVA342E AN-1839 … . I think we have that figured. TP2 VCC on the board is VDIM in the paper and TP4 Dim goes to pin 3 of the LM3404. We used TP4 Dim to control the LED intensity but only got about a 10000 to 1 contrast ratio. Reviewing your paper, I believe we should be feeding our PWM signal into J15 (Conn-1). Is that true and what do we do with TP4 Dim? What is TP2 Vcc (Vdim) for? We are shooting for a minimum of 25000 to 1 contrast ratio. What is J1 (JMP-1) used for. Are there any other papers that can help us with this eval board. The last part of your eval paper in the example 4 portion discusses both the Dim pin operation and the External Mosfet dimming but we could use more information on an circuit diagram for the high ratio dimming. Thank you for your time.