AN2986 datasheet(12/18 Pages) STMICROELECTRONICS

12 / 18 page

Gate current variation

AN2986

12/18

Doc ID 15727 Rev 1

2.3

Maximum current calculation

The maximum current that the MCU can handle is based on the following opposite

conditions:

●

maximum supply voltage (VDDmax),

●

minimum voltage drop of the gate junction (VGTmin),

●

minimum gate resistor (0.99 x RG),

●

minimum output low voltage (VOLmin).

Equation 7

As previously stated, a load RMS current of 1 A for Z0103 and 0.8 A for ACS108-6T is used.

Z01’s minimum VGT is then close to –0.1 V at 1.44 A peak load current in positive half-wave

and for a 125 °C junction temperature (worst case).

ACS108’s minimum VGT is close to 0.6 V for 1.15 A peak load current and for a 125 °C

junction temperature (worst case).

Two examples are shown. The same components are used as those given in Section 1.2.2.

Example 5: MCU: STM8S with ACS108 -6T for power supply 5 V ±10%

Specified values:

RG = 180 Ω, VDD = 5 V, VGT min (0.8 A) = 0.6 V

Calculated values:

VDDmax = 1.1 x 5 V = 5.5 V,

VOLmin IGT = 20 mA) = 0.8 V

IGmax is then given by:

Equation 8

This result exceeds the maximum MCU current capability for one high-sink I/O port. This

IGmax current can be sunk with 2 I/O ports in parallel. Estimation of VOLmin has been

provided for four high-sink I/O ports sinking at the same time 10 mA. VGTmin depends on

load current. A lower load current means higher VGTmin and therefore lower IGmax.

Example 6: STM32 + Z0103 for 3.3 V ±5%

Specified values:

RG = 300 Ω, VDD = 3.3 V, VGT min = –0.1 V

Calculated values:

VDD max = 1.05 x 3.3 V = 3.47 V

VOLmin (IGT = 8 mA) = 0.4 V

IG max is then given by:

Equation 9

Gma x

DDm ax

GTmin

–

OLm in

–

0.99

------------------------------------------------------------------------

Gm ax

5.5

0.6

–

0.8

–

0.99

180

-------------------------------------

23.2mA

Gmax

3.47

0.1

–

()

–

0.4

–

0.99

300

------------------------------------------------

10.7mA

AN2986 датащи(PDF) 12 Page - STMicroelectronics

AN2986 датащи(HTML) 12 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

датащи скачать

ссылки URL