ZHCSK69F August 2019 – November 2021 TPSM82821 , TPSM82821A , TPSM82822 , TPSM82822A , TPSM82823 , TPSM82823A
PRODUCTION DATA
- 1 特性
- 2 应用
- 3 说明
- 4 Revision History
- 5 Device Comparison Table
- 6 Pin Configuration and Functions
- 7 Specifications
- 8 Detailed Description
- 9 Application and Implementation
- 10Power Supply Recommendations
- 11Layout
- 12Device and Documentation Support
8.3.1 PWM and PSM Operation
The TPSM8282x includes a fixed on-time (tON) circuitry. This tON, in steady-state operation in PWM and PSM modes, is estimated as:
In PWM mode, the TPSM8282x operates with pulse width modulation in continuous conduction mode (CCM) with a tON shown in Equation 1 at medium and heavy load currents. A PWM switching frequency of typically 4 MHz is achieved by this tON circuitry.
To maintain high efficiency at light loads, the device enters power save mode seamlessly when the load current decreases. This happens when the load current becomes smaller than half the ripple current of the inductor. The output current at which this occurs can be approximated with the following equation:
In PSM, the converter operates with a reduced switching frequency and with a minimum quiescent current to maintain high efficiency. The on time in PSM is also based on the same tON circuitry. The switching frequency in PSM is estimated as:
In PSM, the output voltage rises slightly above the nominal output voltage in PWM mode. This effect is reduced by increasing the output capacitance.
The forced PWM version of this device, the TPSM8282xA, does not enter PSM (power save mode) at light load currents and stays in CCM (continuous conduction mode) regardless of the output current in order to minimize the output ripple.