Description générale

The MAX40203 is an ideal diode current-switch with for ward voltage drop that is approximately an order of magnitude smaller than that of Schottky diodes. When forward biased and enabled, the MAX40203 conducts with 90mV of voltage drop while carrying currents as high as 1A. During a short-circuit or a fast power-up, the device limits its output current to 2A. The MAX40203 thermally protects itself and any downstream circuitry from over current conditions. This ideal diode operates from a supply voltage of 1.2V to 5.5V. The supply current is relatively constant with load current, and is typically 300nA. When disabled (EN = low), the ideal diode blocks voltages up to 6V in either direction, makes it suitable for use in most low-voltage, portable electronic devices.

The MAX40203 is available in a tiny, 0.77mm x 0.77mm, 4-bump WLP with a 0.35mm bump pitch and a 5-pin SOT23 package. It is specified over the -40°C to +125°C automotive temperature range.

 

Applications

Ordinateurs portables et tablettes

Battery Backup Systems

Powerline Fault Recorders

Cellular Phones

Electronic Toys

USB-Powered Peripherals

Dispositifs médicaux portables

 

Avantages et caractéristiques

Lower Voltage Drop in Portable Applications

14mV Forward Drop at 1mA (WLP)

16mV Forward Drop at 100mA (WLP)

43mV Forward Drop at 500mA (WLP)

90mV Forward Drop at 1A (WLP)

Longer Battery Life

Low Leakage When Reverse-Biased from VDD

10nA (typ)

Low Supply Quiescent Current

300nA (typ), 500nA (max)

Smaller Footprint Than Larger Schottky Diodes

Tiny, 0.77mm x 0.77mm, 4-Bump WLP

5-Pin SOT23 Package

Wide Supply Voltage Range: 1.2V to 5.5V

Thermally Self-Protecting

-40°C à +125°C Plage de température de fonctionnement

 

Description détaillée

The MAX40203 mimics a near-ideal diode. The device blocks reverse-voltages and passes current when forward biased just as a conventional discrete diode does. However, instead of a cut-in voltage around 500mV and a logarithmic voltage current transfer curve, these ideal diodes exhibit a near-constant voltage drop independent of the magnitude of the forward current. This voltage drop is around 43mV at 500mA of forward current.

The near-constant forward voltage drop helps with supply regulation; a conventional diode’s voltage drop typically increases by 60mV for every decade change in forward current. Similar to normal diodes, these ideal diodes also become resistive as the forward current exceeds the specified limit. Unlike conventional diodes, ideal diodes include automatic thermal protection; if the die temperature exceeds a safe limit, they turn off in order to protect themselves and the circuitry connected to them. Like a conventional diode, the ideal diode turns off when reverse biased. The turn-on and turn-off times for enable and disable responses are similar to those of forward and reverse-bias conditions.

The MAX40203 features an active-high enable input (EN) that allows the forward current path to be turned off when not required. The device is disabled when EN is low, and the ideal diode blocks voltages on either side to a maximum of 6V above ground. This feature allows these ideal diodes to be used to switch between power supply sources, or to control which sub-systems are to be pow- ered up. The EN input has an internal weak pullup, it can be left open for normal operation (for -40°C to +85°C), or connect to VDD for full temperature operating range. EN should not be turned on before VDD.

It should be noted, however, that these ideal diodes are designed to be used to switch between different DC sources, and not for rectifying AC. In applications where an input voltage that is negative with respect to ground may be applied to the diode, conventional diodes should be used.

Loading Limitations

Due to the very low quiescent current of these ideal diodes, the internal control circuitry has limited response speed. Therefore, when the load contains significant capacitance and currents are high (> 500mA), both the turn-on time and the turn-off time can be noticeable. In most situations this is unlikely to be an issue, but the source impedance needs to be within certain limits if the source voltage is below 2V. This is because a sufficiently large current surge can drop the input voltage to below the minimum supply, causing the internal circuitry to start to shut down.