ZHCSGR8A September 2017 – July 2018 TPS63710
PRODUCTION DATA.
The basic parameters for choosing an appropriate inductor is saturation current, as well as the dc resistance of the inductor. The TPS63710 is designed such that it operates with an inductance as given in the recommended operating conditions. For best performance, a nominal inductance of 2.2 µH should be used for input voltages below 9 V. For input voltages above 9 V, a nominal inductance of 4.7 µH is preferred to keep the inductor current ripple at a reasonable level.
Similar to a step-down converter, the inductor along with the output capacitor forms a LC filter. For noise-sensitive applications, larger values for the inductance and output capacitance are preferred to get the noise level at the output to very low values.
The peak inductor current depends on the output load, the input voltage VIN, and the output voltage VOUT. The average inductor current equals the load current.
The topology can be simplified to an inverter stage followed by a step-down converter. The equations for calculating the inductor current of a step-down converter therefore also apply. The worst case inductor ripple current occurs at 50% duty cycle which is when VIN = 2 x |VOUT|. The voltage across the inductor is VIN - |VOUT|, which is 0.5 x VIN at 50% duty cycle. With this, Equation 5 and dt = 0.5 x 1/fS, the peak to peak inductor ripple current is defined by Equation 6. The inductor´s saturation current must remain above its peak current which is calculated in Equation 7. Table 5 shows a list of recommended inductors.
Input Voltage | Vendor | comment | Suggested Inductor(1) |
---|---|---|---|
3.1 V to 9 V | Coilcraft | XFL3012-222ME | |
3.1 V to 9 V | Coilcraft | best performance for low input voltage | XFL4020-222ME |
3.1 V to 9 V | Toko | low cost; small size | DFE252012F-2R2M |
3.1 V to 14 V | Coilcraft | XFL4020-472ME | |
3.1 V to 14 V | Würth | 744 383 570 47 |