米6体育平台手机版

ZHCSQK6 May 2022 TPS92643-Q1

PRODUCTION DATA

封装选项

机械数据 (封装 | 引脚)

PWP|16
- MPDS371A

散热焊盘机械数据 (封装 | 引脚)

订购信息

zhcsqk6_oa

7.3.4 Switching Frequency and Adaptive On-Time Control

The TPS92643-Q1 uses an adaptive on-time control scheme and does not have a dedicated on-board oscillator. The one-shot timer is programmed by the R_ON resistor. The on-time is calculated internally using Equation 1 and is inversely proportional to the measured input voltage, V_IN, and directly proportional to the measured CSP voltage, V_CSP.

Equation 1.

t_{O N} = 10 \times 10^{- 12} \times R_{O N} \times (\frac{V_{C S P}}{V_{I N}})

Given the duty ratio of the buck converter is V_CSP/V_IN, the switching period, T_SW, remains nearly constant over different operating points. Use Equation 2 to calculate the switching period.

Equation 2.

T_{S W} = t_{O N} \times (\frac{V_{C S P}}{V_{I N}}) = 10 \times 10^{- 12} \times R_{O N}

The switching frequency is calculated internally using Equation 3.

Equation 3.

f_{S W} = \frac{1}{10 \times 10^{- 12} \times R_{O N}}

The minimum or maximum duty cycle is limited to finite minimum on-time, T_ON(MIN) and minimum off-time, T_OFF(MIN), respectively. As on-time is constant, the frequency is also a dependent on the efficiency of the device, η_REG, excluding inductor and sense resistor losses.

Equation 4.

f_{S W} = \frac{1}{10 \times 10^{- 12} \times R_{O N} \times η_{R E G}}

TI recommends a switching frequency setting between 100 kHz and 2.2 MHz.