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TPS61170: Li-Ion or Lipo desing

Carlos Terraza Velasquez
Prodigy 50 points
Part Number: TPS61170
Other Parts Discussed in Thread: LM3478, TPS61175, TPS55340, PMP9774

Hello,

I am Carlos Terraza from Peregrines Group SAS,

For my new design I am planning to use TPS61170 Boost Regulator

Input Voltage: 3.3 V to 4.2V (Lipo battery)

Output Voltage: 24V

Required Output Current is 200mA max

Also I want to control the output voltage via PWM to lower voltage than 24V

Can I use this part to do that?

Thanks & Regards

Carlos T.

  • 0
    TI__Guru* 78170 points
    As mentioned on the 1st page of the datasaheet, it supports 24V@150mA from 5V input. Your operating condition is outside this range (lower Vin, and higher load), unless your 200mA is a very short period transient. Consider a controller like the LM3478/88 with an external FET.

    You can adjust the output voltage with a PWM signal by using a RC filter to convert it to a dc signal, then feed it to the FB pin through a resistor. Scale your PWM signal pulse width by ratio the FB resistor network. Note that bigger pulse width will leads to lower output voltage.
  • 0 in reply to Youhao Xi
    Prodigy 50 points

    Youhao Xi said:
    As mentioned on the 1st page of the datasaheet, it supports 24V@150mA from 5V input. Your operating condition is outside this range (lower Vin, and higher load), unless your 200mA is a very short period transient. Consider a controller like the LM3478/88 with an external FET.

    You can adjust the output voltage with a PWM signal by using a RC filter to convert it to a dc signal, then feed it to the FB pin through a resistor. Scale your PWM signal pulse width by ratio the FB resistor network. Note that bigger pulse width will leads to lower output voltage.

    Thanks Youhao Xi,

    There is another option with embeded FET? 

    Best regards,

    Carlos T.

  • 0 in reply to Carlos Terraza Velasquez
    TI__Guru* 78170 points
    The engineers who are experts of the boost converters are currently on vacation, and you may have to wait until early next week to get their advice. Note that we call an IC a converter if the switch FET is integrated, and a controller if the FET is external.
  • 0 in reply to Carlos Terraza Velasquez
    TI__Mastermind 40080 points

    Thanks Youhao.

    Hi Carlos,

    Youhao is right, TPS61170 can't output 24V/200mA at Vin=3.3V-5V. You can choose TPS61175 or TPS55340 boost converter.

  • 0 in reply to Helen chen
    Prodigy 50 points

    Helen chen said:

    Thanks Youhao.

    Hi Carlos,

    Youhao is right, TPS61170 can't output 24V/200mA at Vin=3.3V-5V. You can choose TPS61175 or TPS55340 boost converter.

    Hi Helen,

    Thanks for the response. I also want to control the output voltage via a PWM or Easyscale™ protocol like the TPS61170. How i can do that with the  TPS61175 or TPS55340 boost converter.

  • 0 in reply to Carlos Terraza Velasquez
    TI__Mastermind 40080 points
    There's no Easyscale™ protocol for TPS61175 or 55340. But it is easy to change the output voltage. most of the customer's do this way: adjust the output voltage with a PWM signal by using a RC filter to convert it to a dc signal, then feed it to the FB pin through a resistor. you can refer to the TI design PMP9774 or PMP15037 for the concept. they are not of the same usage, but the concept is the same.
  • 0 in reply to Helen chen
    Prodigy 50 points

    Helen chen said:
    There's no Easyscale™ protocol for TPS61175 or 55340. But it is easy to change the output voltage. most of the customer's do this way: adjust the output voltage with a PWM signal by using a RC filter to convert it to a dc signal, then feed it to the FB pin through a resistor. you can refer to the TI design PMP9774 or PMP15037for the concept. they are not of the same usage, but the concept is the same.

    Hi Helen,

    I made this design with WEBENCH® Power Designer and based in PMP15037 to control de output voltage using a external PWM.

    So the question is, I'm doing right?

    http://i64.tinypic.com/2lu8mxc.png

  • 0 in reply to Carlos Terraza Velasquez
    TI__Mastermind 40080 points

    The concept is OK!! And you can calculate the resistor value based on the Vomin,Vomax and the PWM signal level.

  • 0 in reply to Helen chen
    Prodigy 50 points

    Helen chen said:

    The concept is OK!! And you can calculate the resistor value based on the Vomin,Vomax and the PWM signal level.



    The Vout min is 10V, Vout max is 24V the PWM signal is 3.3V and the duty cycle can be changed from 0% to 100%

    The datasheet says: 

    Vout = 1.229 V X (R1/R2  + 1) Assuming R2 = 10K from the datasheet "Considering the leakage current through the resistor divider and noise decoupling into FB pin, an optimum value for R2 is around 10k" 

    So, for Vout max = 24V, R2 = 10k and R1 = 185k

    for Vout min = 10V, R2 = 10k and R1 = 71.3k

    The feedback resistor needed is between 185k and 71.3k?? maybe 128k??
     

  • 0 in reply to Carlos Terraza Velasquez
    TI__Mastermind 40080 points
    OK, but it need some time, please wait in patient.