AN2986 Datasheet, PDF (11/18 Pages) STMicroelectronics – This document focuses on the calculation

AN2986
Gate current variation
The Z01’s maximum V_GT is then close to 1.1 V at 1.44 A peak load current in negative half-
wave, for a 0 °C junction temperature (worst case). A maximum value of 1.3 V is used, as
specified in the Z01 datasheet for 25 °C.
The ACS108’s maximum absolute V_GT is close to 1 V for a 1.15 A peak load current, for
a 0 °C junction temperature (worst case). A maximum value of 1 V is used, as specified in
the ACS108-6T datasheet for 25 °C.
Two examples are shown. The same components are used as those given in Section 1.2.2.
Note that different values than those specified in Table 1 could be used, especially if a
different gate current is applied. Values are then taken from the MCU datasheet curves (for
example.: STM8S10xxx).
Example 3: MCU: STM8S with ACS108 -6T for power supply 5 V ±10%
Specified values: R_G =180 Ω, V_DD = 5 V, V_GT (25 °C) = 1 V
Calculated values: V_DD min= 0.9 x 5 V = 4.5 V
V_GT (0 °C) = 1 + 0.05 V
V_OLmax (25 °C, 16 mA) = 0.6 V
I_Gmin is then given by:
Equation 5
I_Gmin < ⁴----^.-⁵-₁----_.^–-₀---₁-¹---^.-_×-⁰---⁵--₁---–₈----₀₀----^.-⁶-- = 15.7mA
The MCU is able to provide current that is above the minimum gate current for ambient
temperature 0 °C. An estimation of V_OLmax has been provided for one high-sink I/O port of
STM8S up to 16 mA. A standard I/O port could have lower current capability (10 mA), in
which case several I/O ports have to be put in parallel.
Example 4: STM32 + Z0103 for 3.3 V ±5%
Specified values: R_G = 300 Ω, V_DD = 3.3 V, V_GT (25 °C) = 1.3 V
Calculated values: V_DDmin = 0.95 x 3.3 V = 3.13 V,
V_GT (0 °C) = 0.05 + 1.3 V
V_OLmax (I_GT = 8 mA) = 0.4 V
I_Gmin is then given by:
Equation 6
I_Gmin < -³---^.-¹---₁-³--_.--₀-–--₁--¹---_×^.--³----⁵³---₀-–--₀---⁰---^.--⁴--= 4.6mA
The MCU is able to provide current that is above the minimum gate current for ambient
temperature 0 °C. An estimation of V_OLmax has been provided for one I/O port of STM32
(when 8 I/O ports are sunk with 8 mA each at the same time). If the current sunk by one I/O
exceeds 8 mA, the value of 1.3 V should be used instead of 0.4 V.
Doc ID 15727 Rev 1
11/18