ULN2003AI: How to calculate PD_max

Hiromu Susami

Prodigy 660 points

Part Number: ULN2003AI

Tool/software:

Hi exparts,

Could you tell me how to calculate PD_max under following condition?

[Condition]

The on time per pulse is 32.5 ms, and the operation as shown in the attached image is repeated at a period of 260 ms.

Three of the eight steps per channel are on (32.5 ms*3 = 97.5 ms), and two channels are on simultaneously during 1-2 phase excitation for a total of 50% of the period (32.5 ms*4 = 130 ms).

Regards,

Hiromu

over 1 year ago

0 Hiromu Susami over 1 year ago

TI__Prodigy 660 points

Hi team,

Could you give me your support?

Regards,

Hiromu

0 Patrick Shalton over 1 year ago in reply to Hiromu Susami

TI__Mastermind 29530 points

Hi Hiromu-san,

The peak power would be during when 2 channels are on, and would be Imax * VCE,sat., and this would be at 50% duty cycle. What is the max Tamb of the application?

Thanks,

Patrick

0 Hiromu Susami over 1 year ago in reply to Patrick Shalton

TI__Prodigy 660 points

Hi Patrick,

We tried to calculate TJ(MAX) as follows. Could you check whether it is correct or not ?

PD_1ch=VCE*IL*0.375　:The on period per channel is 3/8 = 37.5% 　

PD_max=pd_1ch*4ch 　:Total of 4 channels per cycle

[Calculation (Tamb = 70°C)]

IL=0.300A、VOL=VCE=1.2V (Calculated from characteristic graph)

PD_1ch=VCE*IL*0.375=1.2*0.3*0.375=0.135W

PD_max=pd_1ch*4ch=0.135*4=0.54W

Tj(MAX)=PD(MAX)*θJA+TA=0.54*95+70=121.3℃

Regards,

Hiromu

+1 Patrick Shalton over 1 year ago in reply to Hiromu Susami

TI__Mastermind 29530 points

Hi Hiromu-san,

That calculation works for steady-state power dissipation. However, the instantaneous dissipation will be larger - while 2 channels are on the power dissipation would be:

1.2V * 0.6A = 0.72W

Tj,max = 0.72 * 95 (NS package power dissipation) + 70 = 138C.

Thanks,

Patrick

0 Hiromu Susami over 1 year ago in reply to Patrick Shalton

TI__Prodigy 660 points

Hi Patrick,

If so, should we change something becaouse of Tj,max? It exceeds Tj recommended operation range –40≦Tj≦125.

If we have to change something, what should we do?

Regards,

Hiromu

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ULN2003AI: How to calculate PD_max