TLV61220 With Dimming feature

Sudhir Surnar

Prodigy 120 points

Other Parts Discussed in Thread: TLV61220, TPS61070, TPS61200

Hello Team,

one of my customer wants to add the Dimming feature in a Led lighting application where TLV61220 is used.

can you please help to know how we can add the analog dimming feature here ... the basic specs are as below ...

Specs :

Battery Ratings & Chemistry : : 2.4V, 1200mAH & Rechargeable Ni mH
System O/P : 3v - 3.2v @ 160mAmp
Load Rating : 0.5w Single Led
Features : Analog Two stage Dimming (using Switch)
Dimming Ratings : 1st Dim @ 70% (120mA) & 2nd Dim @ 50%(80mA)

Attached is the concept design used for non dimming requirement earlier.

We are thinking on Op-Amp (LM35x) approach but unable to get the results ...can you please let me know how to add dimming here.3124.7418.0.25w Study Lamp.pdf

over 11 years ago

0 Jasper Li over 11 years ago

TI__Mastermind 46905 points

what is the minimum output voltage of the battery? i'm wandering how to guarantee the TLV61220 output 3V@160mA in your schematic.

if the input voltage reduce to 1.8V. maybe you need to consider other device to support 0.5W output power, like TPS61070.

Thanks

Jasper li

0 Sudhir Surnar over 11 years ago in reply to Jasper Li

Prodigy 120 points

Hi Jasper,

The Battery cut off is maintained at 1.7-1.8 itself ... anyway the min Vin range for TLV61220 is 0.7v so that's not a problem.

Thanks

Sudhir

0 Jasper Li over 11 years ago in reply to Sudhir Surnar

TI__Mastermind 46905 points

i was talking about max output current of TLV61220. if Vin=1.8, Vout=3V, the device can't support 160mA output current.

thanks

jasper li

0 Sudhir Surnar over 11 years ago in reply to Jasper Li

Prodigy 120 points

Hi Jasper,

Yes you are correct ... it's not crossing 125mA range even by 2 Vin & dropping down the efficiency to 60% avg.

Here we tried to use 3 ohm resistor across Led to Vfb pin to regulate output. Also the TPS61070 might also doesn't support as it's Feedback voltage is 500mv Typ.

where as the MP3412 is performing well here.

can you please help to know any other way around to achieve at least 50% dimming (single stage) , now the lower cutoff is set at 1.9Vin .

Thanks & Regards,

Sudhir

0 Jasper Li over 11 years ago in reply to Sudhir Surnar

TI__Mastermind 46905 points

maybe you can refer the application note, using TPS61200 to chieve WLED and dimming.

http://www.ti.com/lit/an/slva364/slva364.pdf

jasper li

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TLV61220 With Dimming feature