SDAA402 July   2026 TPSM82901 , TPSM82902 , TPSM82903

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Detailed Description
    1. 2.1 Inductor Specifications for TPSM8290x
    2. 2.2 Current limit for TPS8290x family if ICs
  6. 3Design Example
  7. 4Applicable operating conditions at 1MHz for TPSM8290x ICs
  8. 5Summary
  9. 6References

3 Design Example

Let us try to demonstrate whether TPSM82903 can be operated for the following conditions

Parameter Value
Min. Input Voltage (Vin_min) 9V
Max. Input Voltage (Vin_max) 13.2 (12V+10%)
Output voltage (Vout_max) 5.2V
Output current 1.1A (1A+10%)
Fsw 1MHz
L_nominal 1uH
L_derated 0.76uH (considering 20% derating on 95% of the actual inductor value)

Step1: Calculate Ton

Equation 1. T O N = V O U T V I N * 1 f s w
Equation 2. T O N = 394 n s

Step 2: Calculate peak inductor current in pulse skip mode, ILPSM

Equation 3. I L P S M ( p e a k ) = ( V I N - V O U T ) L * T O N
Equation 4. I L P S M ( p e a k ) = 4.14 A

With no load, the converter is in PSM (Pulse Skip Mode). The inductor peak current should not cross 4.1A which is the minimum value for High-side FET current limit of TPSM82903. This parameter determines the range of voltage for which the module can be operated.

Step 3: Calculate I L m a x and I L m i n @ Vin_max

Equation 5. I L m a x = I o u t + ∆ I L 2
Equation 6. I L m a x = 1.1 + 4.14 2 = 3.17 A
Equation 7. I L m i n = I o u t - ∆ I L 2
Equation 8. I L m i n = 1.1 - 4.14 2 = - 0.97 A

Negative ILmin implies that the converter is in DCM mode for 1.1A load current. Hence, we would have to use DCM formula to calculate duty cycle given below.

Equation 9. V O U T = V I N * [ 2 * D D + D 2 + 8 * L R * T ]

Calculating for D, we get

Equation 10. D = 0.29

Step 4: Calculate I L m a x with D value from step 3

Equation 11. I L m a x = V I N - V O U T L × f S W   × D
Equation 12. I L m a x = 3.16 A

The peak current is 3.16A which is lower than both rated and saturation current limit of the inductor.

Hence, for the given operating condition, the peak current at no load neither exceeds the current limit of the HSFET nor the rated current of the inductor.