**Part Number:**TPS65150

Hi,

Good Day. Please help to check the customer's query below. I also try to check what he said and I think he has a point. I need your confirmation if his query is correct.

The TPS65150 datasheet I have (SLVS576B –SEPTEMBER 2005–REVISED JANUARY 2016) has calculations in section 7.3.3.1 Positive Charge Pump Output Voltage. There is a note "TI recommends choosing a value for R2 not greater than 1 MΩ".Using this value for a Vo of 20V gives R1=16Meg Ohms. This is way too big for reliable operation. I think the note should say that R1 should not be more than 1 Meg Ohms.

My computation to check the customer's query/

Vo = (1 + R1/R2) * Vref; Vo=30V (maximum output voltage for positive charge pump), R1=1Mohm, Vref=1.214V

R2 = 42.17 kohm

Vo = (1 + R1/R2) * Vref; Vo=30V (maximum output voltage for positive charge pump), R2=1Mohm, Vref=1.214V

R1 = 23.71 Mohm (too big for reliable operation)

*******************************************************************************************************************************************************************************************************************************************

My computation to check if R2 should not be greater than 1Mohm,

Vo = (1 + R1/R2) * Vref; Vref = 1.214V

--------------------------------------------------------------------------------------------------------------------------------------------

if R1 = 1Mohm, R2 = 1kohm

Vo = (1 + 1Mohm/1kohm) * 1.214V = 1214.214V (it exceeds the maximum output voltage of TPS65150)

if R1 = 1Mohm, R2 = 100kohm

Vo = (1 + 1Mohm/100kohm) * 1.214V = 13.354V

--------------------------------------------------------------------------------------------------------------------------------------------

if R1 = 1kohm, R2 = 1Mohm

Vo = (1 + 1kohm/1Mohm) * 1.214V = 1.215214V

if R1 = 100kohm, R2 = 1Mohm

Vo = (1 + 100kohm/1Mohm) * 1.214V = 1.3354V

I just confuse when I check this query on also my computation that's why I ask the forum for clarification and double checking. Thank you very much.

Best Regards,

Ray Vincent Aranzaso

Texas Instruments Customer Support