ST72511R datasheet(24/164 Pages) STMICROELECTRONICS

24 / 164 page

ST72311R, ST72511R, ST72512R, ST72532R

24/164

5.1 LOW VOLTAGE DETECTOR (LVD)

To allow the integration of power management

features in the application, the Low Voltage Detec-

tor function (LVD) generates a static reset when

the VDD supply voltage is below a VIT- reference

value. This means that it secures the power-up as

well as the power-down keeping the ST7 in reset.

The VIT- reference value for a voltage drop is lower

than the VIT+ reference value for power-on in order

to avoid a parasitic reset when the MCU starts run-

ning and sinks current on the supply (hysteresis).

The LVD Reset circuitry generates a reset when

VDD is below:

–VIT+ when VDD is rising

–VIT- when VDD is falling

The LVD function is illustrated in Figure 10.

Provided the minimum VDD value (guaranteed for

the oscillator frequency) is below VIT-, the MCU

can only be in two modes:

– under full software control

– in static safe reset

In these conditions, secure operation is always en-

sured for the application without the need for ex-

ternal reset hardware.

During a Low Voltage Detector Reset, the RESET

pin is held low, thus permitting the MCU to reset

other devices.

Notes:

The LVD allows the device to be used without any

external RESET circuitry.

The LVD is an optional function which can be se-

lected when ordering the device (ordering informa-

tion).

Figure 10. Low Voltage Detector vs Reset

VDD

VIT+

RESET

VIT-

Vhys

ST72511R データシート(PDF) 24 Page - STMicroelectronics

ST72511R データシート(HTML) 24 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

データシートダウンロード