SNAS879 December 2024 LMR60420
PRODMIX
- 1
- 1 Features
- 2 Applications
- 3 Description
- 4 Device Comparison Table
- 5 Pin Configuration and Functions
- 6 Specifications
- 7 Detailed Description
-
8 Application and
Implementation
- 8.1 Application Information
- 8.2
Typical Application
- 8.2.1 Design Requirements
- 8.2.2 Detailed Design Procedure
- 8.2.3 Application Curves
- 8.3 Power Supply Recommendations
- 8.4 Layout
- 9 Device and Documentation Support
- 10Revision History
- 11Mechanical, Packaging, and Orderable Information
7.4.2.3 FPWM Operation - Light Load Operation
In forced pulse width modulation (FPWM) mode, frequency is maintained while lightly loaded. To maintain frequency, a limited reverse current is allowed to flow through the inductor. Reverse current is limited by reverse current limit circuitry, see Section 6.5.
Figure 7-9 FPWM Mode OperationFPWM mode can be achieved in any of the following ways:
- Connect MODE/SYNC directly to RT pin.
- Apply an external voltage across MODE/SYNC and PGND that is greater than VIH(MODE/SYNC).
- Apply an appropriate external clock signal. See Table 7-1.
Under operating conditions where the minimum on-time or minimum off-time can be exceeded, the frequency reduces even while operating in FPWM to maintain minimum timing specifications. Additionally, in cases where the input voltage exceeds VINOVP(R) the LMR60420 prevents negative currents from flowing through the inductor and the LMR60420 implements PFM switching. After the input voltage falls below VINOVP(F), the device again operates in FPWM and allows negative inductor currents.