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TPS61169: TPS61169

Part Number: TPS61169
Other Parts Discussed in Thread: TPS61500,

Im using a tps61500 part for another application

I see the TPS61169 part for a new design but am really unclear what the total current dissipation can be. Datasheet says look at a thermal table but its cryptic

application is a single lipoly 3.7vdc min 2400mA 1C discharge cell

want to drive up to 9 LEDs with max Vf of 2.7vdc at up to 400mA

constant - CW --- no dimming needed at all (i see the min duty says 1% but we wont have any externally fed PWM signal.)

environment is ambient 25C

driving a single string below the stated 1.2A I minimum limit where i have close to 10 watts- in this string--is this possible with this internal FET because i dont see any thermal pad on the bottom side.

there is also a note that internal thermal derating of Iout occurs at 100C

I must be missing something here.

is there maybe another part with integrated FET drive that can work better?

  • Hi since this period is during Chinese mid-autumn festival, out expert will reply you after this Wed. 

  • so can you answer my query on the idea of using tps61169 in this application---can this device source 10W constant current?

  • w is for power and A is for current, i don't understand what you meaning.

  • fully aware of p vs I

    want to drive up to 9 LEDs at  total Vf of 24.3Vdc      --- 24.3x.4 = 9.72 ----- 9.72Watts margined up by my choice to be 12Watts.

    Can this device constant current drive  at 12Watts?

  • since i see no thermal pad on the bottom i doubt that it can thermally handle / dissipate that power.

    so if this wont work might you suggest another solution ---or just stay with the 16500 part -----which is hard to find at suppliers

  • to evaluate the boost converter power dissipation ,  you should base on Vin, Vout, L , and load conditon. you only offer the condition of Vout and Iload, i can't offer a accuracy judgement whether it can satisfy your need or not. please complete the condition about Vin and L.

    ps:10.1 -10.7 is Chinese notional holiday, our expert will reply you after 10.8. if it's an urgent case, please directly communicate with the person who is assigned. 

  • hello, according to your loss formula, the result 9.72W should be the loss of the 9 LEDs.

    And you mentioned that no thermal pad on the bottom, I suppose your concern is the loss dissipation and thermal condition of IC itself? rather than the thermal condition of LEDs.

    If yes, please provide your operation condition for us to evaluate. 

  • hi if there is no more request, I will resolve this. thanks

  • Yes the concern is whether the part can drive 12watts reliably --- constant--not pulsed...i am not concerned at all on the thermal condition of the leds in the string as the pcba the leds are mounted on has excellent 2oz thermal copper reliefs under each LED....really hoping i can finally get some clear opinion on the drive capability of this 61169 part....or will only the tps61500 part that  is currently used the only real solution? Frankly im dubious that this 61169 part can in fact handle the power requirements. An answer either way would be great to proceed from:)

  • yes, I understand your concern. We can have a brief evaluation on the thermal condition.

    As you know, there is no thermal pad in 61169, and the thermal resistance can be up to 263.8℃/W. 

    The loss in IC can be handled is (150-25)/263.8=0.474W.

    For Vin=3.7V, Po=9.7W, Eff=0.9, the input current is quite high, and the max Rds_on of main FET is 0.7Ω. I think the total IC loss will not below 0.474W.

    I will check if any other IC can be used.

  • ok thank you ----kind of pressed timewise to resolve so please advise on your alternate possibility.

    there are many with external fet drives that would work but hoping to find an integrated solution with fet drive-----space constraints and all....otherwise might you know what the forecasting will be if i stay with 61500 which seems to be loe now on availability?

  • So right now for 61500, the problem is that you cannot buy due to out of storage online? 

    For other integrated Fet products, it seems cannot satisfy the thermal requirement.