Field effect tube |MOSFET|MOS tube - BYCHIP

1. Anti-burn MOS tube


The application position of the anti-burn MOS is as follows: in the mobile phone charging line, the VBUS is wired, and an NMOS is connected in parallel. The D pole of the MOS tube is connected to the VBUS, the S pole is grounded, and the G pole is connected to the AP. Through the AP, the anti-burn MOS is opened and closed. The anti-burn MOS tube is mainly opened when water, foreign matter or short circuit is detected in the charging port during the charging process. The charging current flows through the anti-burn MOS tube, which is equivalent to shorting the VBUS to the ground through a small resistance. At this time, the current will exceed the maximum output current of the charger, triggering the short-circuit protection of the charger output. The charger will overcurrent to protect no voltage output. Thus, it has a protective effect.

An important difference between anti-burn MOS tube and ordinary power MOS tube is low Vth, such as PMPB13XNE Vth maximum 0.9V, this is because the current GPIO voltage of the mobile phone platform is 1.8V, if the Vth is larger 1.8V cannot guarantee that the MOS is fully turned on.

Application location diagram of anti-burn MOS tube.


The actual schematic connection relationship is as follows. The following is the schematic of a project of a customer.


The current models of anti-burn MOS tubes used by several mobile phone customers are as follows:

Table 1


2. Green Factory VOOC direct charging road


Refer to the second article I wrote charging 5 minutes for 2 hours - OPPO VOOC fast charging road, Green Factory VOOC direct charging with 2 back-to-back NMOS, one for OVP, one for anti-leakage. The MOS tube models used are included in the models for OVP mentioned below, Table 2.


Three. Do OVP switch


At the input end of the Chargepump charging IC, a series MOS tube acts as the OVP switch, and the G pole of the MOS tube is controlled by the Chargepump OVP_DRV pin. When the output voltage reaches the OVP threshold, the charging IC shuts down the MOS tube to protect the charging IC.


At present, some customers mainly use MOS tube models as follows:

Table 2


Four. Do OVP switch + anti-leakage


When wireless charging and wired charging use the same charging IC (Chargepump), two NMOS are connected in series on the wireless charging path and two NMOS are connected in series on the wired charging path. If only one MOS tube is connected in series as in the previous section, For example, the yellow path - when wired charging, the voltage will leak through the parasitic diode of the MOS tube to the output end of the wireless charging IC, or the red path - when wireless charging, the voltage will leak through the parasitic diode of the MOS tube to the Type-C interface. Two of them in parallel back to back solves the problem. MOS tube models refer to Table 2.


Of course, some customers do not use the same charging chip for wired charging and wireless charging, and some customers will separately add a low-power Chargepump charging IC for wireless charging. In this scheme, only one MOS can be used at the wired charging end.