UM0969 datasheet(13/46 Pages) STMICROELECTRONICS

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UM0969

Board description

Doc ID 17665 Rev 2

13/46

The brake function can be also activated by the microcontroller thanks to the motor control

connector (connector J3, pin 23 PWM_BRAKE signal). The brake threshold levels can be

modified by calculating R83, R85, and R86 new values.

2.3.4

Overcurrent protection (OCP)

On the STEVAL-IHM027V1 a simple overcurrent HW protection has been implemented. The

three TSV994 outputs (pin 1, 7, 8) are the inputs for a discrete OR logic (realized with

diodes D6,D7,D8). OR logic output, the biggest op-amp output voltage, is compared to a

fixed threshold voltage (set by the R52-R49 voltage divider). When this threshold is passed,

transistor Q1 is switched on, setting the enable signals to 0 V (/G1/G2) of M74HC367 and

interrupting the PWM signal path, from the MCU to the STGIPS10K60A logic input. When

an OCP event occurs, the FAULT signal (connector J3, pin 1 FAULT signal) is also activated

to communicate with the MCU. The current protection limit value is also defined by the

current sensing amplifying network, described in the next paragraph, because its value must

be chosen according to the maximum amplifiable current without distortions. With the

chosen value, the STEVAL-IHM027V1 OC protection limit is set to 6 A.

The OCP can be disabled by moving the jumper W16 from position “A” to position “B”. It is

possible to reach a higher current value but the demonstration board does not protect itself

during an overcurrent event. This test must be carried out by skilled technical personnel

according to the common accident prevention rules.

2.3.5

Current sensing amplifying network

Three-shunt current reading configuration

Three-shunt current reading configuration details are shown in Figure 6. The alternating

signal on the shunt resistor, with positive and negative values, must be elaborated to be

compatible with the positive input of the microcontroller A/D converter.

Figure 6.

Three-shunt configuration

UM0969 数据表(PDF) 13 Page - STMicroelectronics