ST7260E1 STMicroelectronics, ST7260E1 Datasheet - Page 126

• Manufacturer Part Number: ST7260E1
• Description: LOW SPEED USB 8-BIT MCU FAMILY WITH UP TO 8K FLASH/ROM AND SERIAL COMMUNICATION INTERFACE (SCI)
• Manufacturer: STMicroelectronics

Specifications of ST7260E1

• 4 Or 8 Kbytes Program Memory: high density Flash (HDFlash), or FastROM with readout and write protection

Electrical characteristics
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RESET pin protection when LVD is enabled
When the LVD is enabled, it is recommended to protect the RESET pin as shown in
Figure 64
1.
2.
3.
4.
5.
6.
Tips when using the LVD:
●
●
●
Figure 64. RESET pin protection when LVD is enabled
EXTERNAL
RESET
The reset network protects the device against parasitic resets.
The output of the external reset circuit must have an open-drain output to drive the ST7
reset pad. Otherwise the device can be damaged when the ST7 generates an internal
reset (LVD or watchdog).
Whatever the reset source is (internal or external), the user must ensure that the level
on the RESET pin can go below the V
Otherwise the reset will not be taken into account internally.
Because the reset circuit is designed to allow the internal RESET to be output in the
RESET pin, the user must ensure that the current sunk on the RESET pin (by an
external pull-up for example) is less than the absolute maximum value specified for
I
When the LVD is enabled, it is mandatory not to connect a pull-up resistor. A 10nF pull-
down capacitor is recommended to filter noise on the reset line.
In case a capacitive power supply is used, it is recommended to connect a 1M ohm
pull-down resistor to the RESET pin to discharge any residual voltage induced by this
capacitive power supply (this will add 5µA to the power consumption of the MCU).
Check that all recommendations related to reset circuit have been applied (see section
above)
Check that the power supply is properly decoupled (100 nF + 10 µF close to the MCU).
Refer to AN1709. If this cannot be done, it is recommended to put a 100 nF + 1M Ohm
pull-down on the RESET pin.
The capacitors connected on the RESET pin and also the power supply are key to
avoiding any start-up marginality. In most cases, steps 1 and 2 above are sufficient for a
robust solution. Otherwise: Replace 10nF pull-down on the RESET pin with a 5 µF to
20 µF capacitor.
INJ(RESET)
and follow these guidelines:
Required
in
0.01 μF
Section 16.2 on page
1 MΩ
Optional
(note 6)
V
DD
111.
R
ON
IL
Filter
max. level specified in
GENERATOR
PULSE
Section
INTERNAL
RESET
WATCHDOG
LVD RESET
16.9.1.
ST72XXX
ST7260xx