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Summary of Contents for tps61040dbvr

Page 1: ...ow to drive white light LEDs To summarize regulation of the LED current is accomplished by monitoring the voltage across a current sense resistor Any power dissipated by the current sense resistor is lost and reduces battery life The key to extending battery life is to reduce the losses in the current sense resistor Figure 1 shows a TPS61040 low power dc dc boost converter application that drives ...

Page 2: ...rs this is not an option because the reference voltage is internally generated and is not user adjustable A second way to reduce losses in the circuit is to inject another voltage into the circuit to bias up the FB pin under no load conditions With an additional resistor the circuit may be designed such that the full scale voltage across the current sense resistor is less than 2 V for a 20 mA outp...

Page 3: ... R4 Vcs Iout_max R2 Rbias Vadj_max Vfb Vcs Vfb Vadj_min Vadj_max Vfb Vb Vcs R3 Vfb Vcs Rbias R2 R2 Vb R2 Vfb Rbias Vadj_min Rbias Vfb Where Vcs is the desired maximum voltage across the current sense resistor Iout_max is the maximum LED current Rbias is the chosen value for the additional bias resistor Vadj_min is the minimum voltage used to adjust the LED current Vadj_max is the maximum voltage u...

Page 4: ...educed The battery life is calculated using a 1000 mA hr Li Ion battery Table 1 Calculated Resistor Values Vcs V 0 5 0 5 0 5 0 25 0 25 0 25 Vbias V 3 3 5 12 7 3 3 5 12 7 Rbias kΩ 499 499 499 499 499 499 R2 kΩ 1466 804 264 3430 1882 618 R3 kΩ 222 122 40 260 143 47 R4 Ω 25 25 25 12 5 12 5 12 5 Table 2 Measured Data Shows Extended Battery Life Vcs V 2 0 5 0 5 0 25 0 25 Vbias V N A 5 Vout 1 5 Vout 2 I...

Page 5: ...nt that any license either express or implied is granted under any TI patent right copyright mask work right or other TI intellectual property right relating to any combination machine or process in which TI products or services are used Information published by TI regarding third party products or services does not constitute a license from TI to use such products or services or a warranty or end...

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