SLVSHP0 July 2024 TLVM14404 , TLVM14406
PRODUCTION DATA
The TLVM1440x has an adjustable output voltage range from 0.8V up to a maximum of 9V or slightly less than VIN, whichever is lower. Setting the output voltage requires two feedback resistors, designated as RFBT and RFBB in schematics. The reference voltage at the feedback (FB) pin is set at 0.8V with a feedback system accuracy over the full junction temperature range of ±1%. The junction temperature range for the device is –40°C to 125°C.
Calculate the value for RFBB using Equation 4 below based on a recommended value for RFBT of 100kΩ.
Table 7-4 lists the standard resistor values for several output voltages and the recommended switching frequency range to maintain reasonable peak-to-peak inductor ripple current. This table also includes the minimum required output capacitance for each output voltage setting to maintain stability. The capacitances as listed represent effective values for ceramic capacitors derated for DC bias voltage and temperature. Furthermore, place a feedforward capacitor, CFF, in parallel with RFBT to increase the phase margin when the output capacitance is close to the minimum recommended value.
VOUT (V) | RFBT (kΩ) (1) | RFBB (kΩ) (1) | SUGGESTED FSW RANGE (kHz) | COUT(min) (µF), Per Phase (EFFECTIVE) | BOM(2) | CFF (pF) |
---|---|---|---|---|---|---|
0.8 | 10 | Open | 300 to 700 | 470 | 1 × 47μF (6.3V), 1 × 470μF (2.5V) | — |
1.8 | 12.4 | 10 | 300 to 1000 | 125 | 3 × 47μF (6.3V), 1 × 22μF (6.3V) | 330 |
3.3 | 31.2 | 10 | 500 to 1300 | 64 | 4 × 22μF (10V) | Internal |
5 | 52.3 | 10 | 700 to 2100 | 64 | 4 × 22μF (10V) | Internal |
9 | 105 | 10 | 1200 to 2100 | 40 | 3 × 22μF (16V) | 4.7 |
Note that higher feedback resistances consume less DC current. However, an upper RFBT resistor value higher than 1MΩ renders the feedback path more susceptible to noise. Higher feedback resistances generally require more careful layout of the feedback path. Make sure to locate the feedback resistors close to the FB and AGND pins, keeping the feedback trace as short as possible (and away from noisy areas of the PCB). See Layout Example guidelines for more detail.