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February 8, 2019
The R3201 is a special IC dedicated for portable devices with a built-in battery and which need the possibility to reset the software to resume normal operation. Additionally it provides a so-called shipping mode to reduce current consumption when the device is stored in a warehouse or during shipment. Target applications are mobile phones, tablets, cameras, medical devices, wearables, portable game consoles, music players etc.
Due to the complex level of functionality nowadays available on portable devices, there is a possibility that it may lock up due to a software malfunction. In such case, one has to initiate a reset cycle to return to normal operation. It can be done in several ways like pressing a dedicated reset switch or by pressing and hold two available keys for a certain time. In worst case, the batteries may have to be removed.
The R3201 was especially developed for this kind of requirement and will provide a reset cycle to the application processor that is long enough to reset properly. The R3201 has two independent reset request inputs (RST0, RST1) to connect a single reset switch or by using two available device buttons. In order to prevent an accidental reset cycle, these switches need to be activated and held for a certain period. The delay time options are 8 / 10 / 12 or 16 seconds, which are internally fixed by product version. Once the reset cycle is triggered, an actual reset period of 0.4 seconds will be provided.
Both RST0 and RST1 input pins have an incorporated debounce circuit with a delay time of 10 msec.
Another important feature of the R3201 is the shipping mode, this kind of operating mode is very important when the device is stored in a warehouse for a long time or during shipment. Devices with internal or pre-installed batteries that are stored for too long in standby mode will drain the batteries and may be completely exhausted before being delivered to the customer for initial use.
The main advantage of the R3201 compared to a conventional reset timer IC is its ability to minimize current consumption of the device in the shipping mode. When a device is set into the standby mode, some components like the reset timer remain in On-mode whilst all other ICs are set to the Off mode. However, even in Off-mode there is still an amount of leakage current caused by these ICs.
The application processor is able to send a short clock pulse burst to the “Off” input pin and the R3201 will switch to the shipping mode after 15 seconds. As a result, the nSRO output will control an external MOSFET disconnecting the battery line from the circuit, in this way the Off-mode leakage current is avoided and prolongs battery life significantly. The output has a specific slew rate in order to switch the power supply smoothly. The second SRO output is used, for example, to control an LDO or DC/DC Converter to the standby mode.
The shipping mode is released by activating the Power-On button for more than 2 seconds or by applying a power adapter to the device and being detected by the TAIN input. The breakdown voltage of TAIN pin is 12 V, but can be extended to 30 V by using a resistor of 100 kΩ in series. In the shipping mode all redundant circuits are isolated from the power supply and the remaining current consumption of the R3201 is only 0.35 µA.
Shipping Mode Timing Chart
The R3201 has two (N-channel open drain) discharge outputs, called DCHG1 and DSCHG2. The goal is to discharge output capacitors to ground during the reset cycle ensuring that the power lines are completely de-energized.
The new R3201 reset timer is a very useful tool for portable devices which need a proper reset cycle to recover from a software malfunction, moreover the additional shipping mode prolongs battery life when the device is stored on the shelf for a long period. It needs only a few external components whilst the package dimensions are very small, this will assure the use of a very small PCB area.