SLVSFQ9 Data sheet

SLVSFQ9A August 2021 – November 2021 TPSM8A28 , TPSM8A29

PRODUCTION DATA

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Mechanical Data (Package|Pins)

RDG|25
- MPQF603

Thermal pad, mechanical data (Package|Pins)

Orderable Information

8.2.2.7 EN Pin Resistor Divider

A resistor divider on the EN pin can be used to increase the input voltage the converter begins its startup sequence. To set the start voltage, first select the bottom resistor (R_{EN_B}). The recommended value is between 1 kΩ and 100 kΩ. There is an internal pulldown resistance with a nominal value of 6 MΩ. This must be included for the most accurate calculations. This is especially important when the bottom resistor is a higher value, near 100 kΩ. This example uses a 10-kΩ resistor and this combined with the internal resistance in parallel results in an equivalent bottom resistance of 9.98 kΩ. The top resistor value for the target start voltage is calculated with Equation 22. In this example, the nearest standard value of 20 kΩ is selected for R_{EN_T}. When selecting a start voltage in a wide input range application, be cautious that the EN pin absolute maximum voltage of 6 V is not exceeded.

Equation 22.

R_{E N_T} = \frac{R_{E N_B} \times V_{s t a r t}}{V_{E N H}} - R_{E N_B} = \frac{10 k Ω \times 3.7 V}{1.22 V} - 10 k Ω = 20 k Ω

The start and stop voltages with the selected EN resistor divider can be calculated with Equation 23 and Equation 24, respectively.

Equation 23.

V_{s t a r t} = V_{E N H} \times \frac{R_{E N_T} + R_{E N_B}}{R_{E N_B}} = 1.22 V \times \frac{20 k Ω + 10 k Ω}{10 k Ω} = 3.66 V

Equation 24.

V_{s t o p} = V_{E N L} \times \frac{R_{E N_T} + R_{E N_B}}{R_{E N_B}} = 1.02 V \times \frac{20 k Ω + 10 k Ω}{10 k Ω} = 3.06 V