SLUSE80A September 2021 – November 2021 UCC14240-Q1

ADVANCE INFORMATION

- 1 Features
- 2 Applications
- 3 Description
- 4 Revision History
- 5 Pin Configuration and Functions
- 6 Specifications
- 7 Detailed Description
- 8 Application and Implementation
- 9 Power Supply Recommendations
- 10Layout
- 11Device and Documentation Support
- 12Mechanical, Packaging, and Orderable Information

- DWN|36

The R_{LIM} resistor chosen
can provide enough current for the load using the following equations, whichever has
lower R_{LIM} value. Equation 1 shows source current due to capacitor variation and IQ. Equation 2 shows sink current due to capacitor variation and IQ.

Equation 1.
${R}_{LIM\_MAX}=\frac{\left(VDD-COM\right)}{\left(\frac{{C}_{OUT3}\times \left(1-\u2206{C}_{OUT3}\right)}{{C}_{OUT2}\times \left(1-\u2206{C}_{OUT2}\right)+{C}_{OUT3}\times \left(1-\u2206{C}_{OUT3}\right)}-\frac{{C}_{OUT3}}{{C}_{OUT2}+{C}_{OUT3}}\right)\times {Q}_{gtot}\times {f}_{SW}+\left({I}_{Q\_DRIVER\_VEE}-{I}_{Q\_DRIVER\_VDD}\right)}-{R}_{LIM\_INT}$

Equation 2.
${R}_{LIM\_MAX}=\frac{\left(VEE-COM\right)}{\left(\frac{{C}_{OUT2}\times \left(1-\u2206{C}_{OUT2}\right)}{{C}_{OUT2}\times \left(1-\u2206{C}_{OUT2}\right)+{C}_{OUT3}\times \left(1-\u2206{C}_{OUT3}\right)}-\frac{{C}_{OUT2}}{{C}_{OUT2}+{C}_{OUT3}}\right)\times {Q}_{gtot}\times {f}_{SW}+\left({I}_{Q\_DRIVER\_VEE}-{I}_{Q\_DRIVER\_VDD}\right)}-{R}_{LIM\_INT}$

where

- Q
_{gtot}is the total gate charge of power switch. - f
_{SW}is the switching frequency of gate drive load. - I
_{Q_DRIVER_VDD}is the maximum quiescent current of the gate driver from (VDD – COM), and any current pulled from VDD by external logic must be included. - I
_{Q_DRIVER_VEE}is the maximum quiescent current of the gate driver from (COM – VEE), and any current pulled from VEE by external logic must be included.

R_{LIM} value determines
response time of (COM – VEE) regulation. Too low an R_{LIM} value can cause
oscillation and can overload (VDD – VEE). Too high an R_{LIM} value can give
offset errors, due to slow response. If R_{LIM} is greater than above
calculations, then there is not enough current available to replenish the charge to
the output capacitors, causing a charge imbalance where the voltage is not able to
maintain regulation, and eventually exceeds the OVP2 or UVP2 FAULT thresholds and
shutting down the device for protection.