JAJSIA2B December 2019 – February 2022 TPS6594-Q1
PRODUCTION DATA
The VCCA pin provides power to the LDOVINT regulator and other internal functions. It is always connected in parallel with the buck input pins (PVIN_Bx pins). The VSYS_SENSE pin and OVPGDRV pin protect the device from being damaged by an overvoltage event from the pre-regulator by disconnecting the low voltage VCCA-powered pins from VSYS. The VCCA pin can be connected to an optional 0.47-µF bypass capacitor close to the pin. For cases where the pre-regulator is not located near the device, place some additional bulk capacitance before the protection FET to stabilize the VSYS supply near the device.
For the input protection, the total amount of capacitance on the VSYS and VCCA node must be large enough to ensure that the voltage at the VCCA pin does not rise above 8 V before the PMIC disables the protection FET in case of pre-regulator high side FET short failure. For a system with 5 V input supply, the specified rise-time in the 6 V to 8 V range is equal or greater than 7-µs. For a system with 3.3 V input supply, the specified rise-time in the 4 V to 8 V range is equal or greater than 7-µs. The capacitance varies based on the pre-regulator inductor and the pre-regulator input filter and it is recommended to simulate this circuit to get an initial estimate on the required capacitance.
Choose a zener diode with a breakdown voltage less than the recommended maximum of the VSYS_SENSE pin (12 V maximum) and greater than the overvoltage detection voltage (VSYS_OVP_Rising of 6.2 V) at all times for proper protection. Choose the protection resistors values to assure that the voltage across the Zener diode remains within those two boundaries and that the current is not greater than the Zener diode maximum current for the full desired input voltage protection range. For increased reliability, two resistors with 90° physical orientation offset are recommended to reduce risk of a single point short resulting in IC damage.
Finally, choose the protection NMOS FET with sufficient current and voltage ratings for the application with minimal gate charge values. The turn-on and turn-off time of the protection FET is generally very fast relative to the detection time, so gate charge is not as critical as RDSON in general. The components chosen for the evaluation module to cover a broad set of applications are shown in Table 9-1. To determine the required minimum FET RDS(ON), the maximum input current is first measured or calculated based on output current requirements multiplied by the duty cycle (VOUT / VIN) and then divided by the buck efficiency. Next, determine the VCCAUV_TH from the VCCA_PG_WINDOW. VCCA_UV_THR register setting. The RDS(ON) maximum must be less than the VCCAUV_TH minimum divided by the input current maximum to ensure that VCCA does not drop below VCCAUV_TH at maximum loading. From there, the second factor to consider is to minimize the QGS for faster FET turn off time.
For cases where input voltage protection is not required, ground VSYS_SENSE, float OVPGDRV, and the protection diode and FET are not needed.
COMPONENT | MANUFACTURER | PART NUMBER | VALUE | EIA SIZE CODE | SIZE (mm) | USED for VALIDATION |
---|---|---|---|---|---|---|
Capacitor | Murata | GCM155C71A474KE36 | 0.47 µF, 10 V, X7R | 0402 | 1.0 × 0.5 | Yes |
Capacitor | TDK | CGA2B3X7S1A474K050BB | 0.47 µF, 10 V, X7R | 0402 | 1.0 × 0.5 | — |
Zener Diode | ON Semiconductor | MM3Z10VST1G | 10 V, 300 mW | SOD-323 | 2.5 × 1.25 × 0.9 | Yes |
Zener Diode | Vishay-Dale | BZX84B10-G3-08 | 10 V, 300 mW | SOT-23-3 | 3.1 × 2.6 × 1.15 | — |
Resistor(1) | Vishay-Dale | CRCW0402240RJNED | 240 Ω | 0402 | 1.0 × 0.5 | Yes |
NMOS FET | On Semiconductor | NVMFS4C05N | 30 V, 4.0 mΩ, 127 A | — | 5.15 × 6.15 × 1.0 | Yes |
NMOS FET | Diodes Incorporated | DMNH3010LK3 | 30 V, 11.5 mΩ, 50 A | — | 6.70 × 10.41 × 2.39 | — |