AN2846 datasheet(12/35 Pages) STMICROELECTRONICS

12 / 35 page

Application guidelines

AN2846

12/35

Doc ID 15130 Rev 1

1.3.2

Power loss detection

For a greater voltage drop on VC, a power supply loss detection has been added. This

immediately sets MISO output at low level state when VC is below 8 V, as shown in

Figure 15 and Figure 16. The MCU can then interpret that if all bits are equal to 0, this

means that VC is too low.

1.3.3

Overtemperature detection

When the junction temperature exceeds 150 °C an overtemperature alarm sets the MISO

bit 6 at low state in the control bits register. The SCLT3-8 remains operational. The MCU

receiving the alarm has to take the corrective actions. The alarm will be reset when the

junction temperature falls below 135 °C.

1.3.4

Internal voltage regulator 5 V

The input of this voltage regulator is internally connected to the VC pin. The voltage

regulator supplies the digital part of the SCLT3-8 and therefore it defines the high digital

level. It also supplies the sourced current available at pin MISO. It can also supply

application needs (such as opto-couplers and micro transformers) through pin VDD. Its total

current capability is 9 mA for a 3% voltage drop on VDD (see Figure 17).

Figure 13.

VCC = 24 V, UVA bit not activated

Figure 14.

VCC = 16 V, UVA bit activated

= 24 V

MISO

SCK

/CS

MISO

SCK

/CS

= 16 V

MISO

SCK

/CS

MISO

SCK

/CS

Figure 15.

Communication stops for VC < 8 V

Figure 16.

Communication resumes for

VC > 8.1 V

8.0 V

MISO goes to L

/CS

SCK

MISO

8.1 V

/CS

SCK

MISO

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