米6体育平台手机版

ZHCSQT8 October 2023 LM74930-Q1

PRODUCTION DATA

封装选项

机械数据 (封装 | 引脚)

RGE|24
- MPQF124G

散热焊盘机械数据 (封装 | 引脚)

RGE|24
- QFND703

订购信息

zhcsqt8_oa

8.2.2.6 Overcurrent Limit (ILIM), Circuit Breaker Timer (TMR), and Current Monitoring Output (IMON) Selection

Programming the Overcurrent Protection Threshold – R_ILIM Selection

The R_ILIM sets the overcurrent protection (circuit breaker detection) threshold, whose value can be calculated using Equation 15.

Equation 15.

R_{I L I M} = \frac{12 {\times R}_{S E T}}{I_{L I M} \times R_{S E N S E}}

To set 5 A as overcurrent protection threshold, R_ILIM value is calculated to be 120 kΩ. Choose available standard value: 120 kΩ, 1%.

Programming the Circuit Breaker Time – C_TMR Selection

For the design example under discussion, overcurrent transients are allowed for 1-ms duration. This blanking interval, T_OC (or circuit breaker interval, T_CB) can be set by selecting appropriate capacitor C_TMR from TMR pin to ground. The value of CTMR can be calculated using Equation 16.

Equation 16.

T_{O C} = 1.2 \times \frac{C_{T M R}}{82.3 μ A}

C_TMR value of 68 nF, 10% is selected to allow circuit breaker duration of close to 1-ms.

Programming Current Monitoring Output – R_IMON Selection

Voltage at IMON pin V_IMON is proportional to the output load current. This can be connected to an ADC of the downstream system for monitoring the operating condition and health of the system. The R_IMON must be selected based on the maximum load current and the input voltage range of the ADC used. R_IMON is set using Equation 17.

Equation 17.

V_{I M O N} = \frac{0.9 \times V_{S E N S E} \times R_{I M O N}}{R_{S E T}}

For this application example, V_IMON is selected to be 2.7 V at full load current of 5 A. R_IMON value of 30.1 kΩ, 1% is selected.