SLUSDP0A August 2019 – May 2021 TPS53676
PRODUCTION DATA
The ON_OFF_CONFIG command controls the conditions which TPS53676 requires to enable power conversion. By default only the AVR_EN (active high) pin enables channel A, and only the BVR_EN pin (active high) enables channel B. This command can program the controller ignore the VR_EN pins and require the OPERATION command to be sent to enable power conversion, or even require a combination of the two.
When enabled, first the controller waits for a delay time given by TON_DELAY, then ramps the output voltage at a controlled slew rate SRBOOT. The device requires 750 μs typically (up to 1.0 ms), to begin ramping the output voltage, after being enabled. Turn-on delay added by the TON_DELAY is in addition to this delay.
The ON_OFF_CONFIG command also controls the turn-off behavior. When configured for immediate-off, the controller immediately tri-states all PWM pins assigned to that channel and stops transferring power immediately. When configured for soft-off the controller first waits for the TOFF_DELAY time, then actively ramps down the output voltage at a controlled slew rate.
The TON_RISE and TOFF_FALL commands are used to calculate the turn-on and turn-off (in the case of soft-off) slew rates. While these commands are numerically programmable from 0 to 31.75 ms, only a limited set of slew rates are supported. During the enable time period, the device calculates the target rising and falling slew rates according to Equation 1 and Equation 2, then selects the nearest available value from Table 7-4.
Supported slew rates (mV/μs) | |
---|---|
0.093 | 0.313 |
0.097 | 0.625 |
0.101 | 0.938 |
0.105 | 1.250 |
0.111 | 1.563 |
0.117 | 1.875 |
0.124 | 2.188 |
0.131 | 2.50 |
0.140 | 5.00 |
0.151 | 10.00 |
1.163 | 15.00 |
0.175 | 20.00 |
0.192 | 25.00 |
0.213 | 30.00 |
0.238 | 35.00 |
0.265 | 40.00 |
Example: VOUT_COMMAND = 0.88 V, TON_RISE = 1.0 ms
The target slew rate is calculated as SRBOOT = LOOKUP(880 mV/1000 μs) = 0.88 mV/μs. The nearest supported value of 0.9375 mV/μs is selected.
The expected rise time is approximately (880 mV / 0.9375 mV/μs) ≈ 940 μs.