ZHCSM62C September 2020 – December 2021 TPS542A50
PRODUCTION DATA
The TPS542A50 uses a programmable soft-start rate to gradually ramp the output voltage reference to reduce inrush currents. The device prevents current from being discharged from the output during start-up when a pre-biased condition exists. No switching pulses occur until the internal soft-start reference exceeds the voltage on the error amplifier input voltage (RSP and RSN pins). The TPS542A50 supports the output voltage with pre-biased up to 100%.
The soft-start clock in Table 7-5 can be programmed on the SS/PFM pin along with enabling/disabling PFM and hiccup time. These same options can also be programmed through the I2C interface. The SS/PFM pin can be shorted to ground to reduce BOM component count. When shorted to ground the default soft-start slew rate is used, and PFM is disabled. If the user programs these functions frequently using the I2C interface, TI recommends shorting the SS/PFM pin to ground to reduce component count. The soft-start timing in Table 7-6 can be programmed based upon the output voltage and soft-start clock. There are four choices of soft-start times to select different soft-start clocks. To prevent an OC fault trigger at start-up, it is recommended to increase the length of soft-start time to reduce the inrush current from exceeding the peak current limit. Using 1-V output voltage as an example, the soft-start time equals to 1.8 ms at 0.5-MHz SS CLK and 0.45 ms at 2.0-MHz SS CLK.
| RSS/PFM (kΩ) | PFM | SS CLK (MHz) | HICCUP DURATION (ms) |
|---|---|---|---|
| Short | Disable | 1.0 | 25.2 |
| 7.5 | Enable | 2.0 | 12.6 |
| 18.2 | 1.0 | 25.2 | |
| 26.1 | 0.50 | 50.4 | |
| 35.7 | 0.25 | 100.8 | |
| 47.5 | Disable | 2.0 | 12.6 |
| 61.9 | 1.0 | 25.2 | |
| 78.7 | 0.50 | 50.4 | |
| 102 | 0.25 | 100.8 |
| VSET (V) | VOUT (V) | LSB SIZE (mV) | SS TIMING (ms) AT CLK: 2.0 MHz | SS TIMING (ms) AT CLK: 1.0 MHz | SS TIMING (ms) AT CLK: 0.5 MHz | SS TIMING (ms) AT CLK: 0.25 MHz |
|---|---|---|---|---|---|---|
| 0.1 | 0.5 | 0.112 | 0.45 | 0.9 | 1.8 | 3.6 |
| 0.2 | 1 | 0.223 | 0.45 | 0.9 | 1.8 | 3.6 |
| 0.28 | 1.4 | 0.313 | 0.45 | 0.9 | 1.8 | 3.6 |
| 0.3 | 1.5 | 0.167 | 0.9 | 1.8 | 3.6 | 7.2 |
| 0.4 | 2.0 | 0.223 | 0.9 | 1.8 | 3.6 | 7.2 |
| 0.5 | 2.5 | 0.279 | 0.9 | 1.8 | 3.6 | 7.2 |
| 0.56 | 2.8 | 0.313 | 0.9 | 1.8 | 3.6 | 7.2 |
| 0.6 | 3.0 | 0.167 | 1.8 | 3.6 | 7.2 | 14.4 |
| 0.7 | 3.5 | 0.195 | 1.8 | 3.6 | 7.2 | 14.4 |
| 0.8 | 4 | 0.223 | 1.8 | 3.6 | 7.2 | 14.4 |
| 0.9 | 4.5 | 0.251 | 1.8 | 3.6 | 7.2 | 14.4 |
| 1 | 5.0 | 0.279 | 1.8 | 3.6 | 7.2 | 14.4 |