Datasheet AOZ6762DI (Alpha & Omega) - 8

AOZ6762DI Protection Features
circuit, the RMS value of input capacitor current can be calculated by: The AOZ6762DI has multiple protection features to prevent system circuit damage under abnormal V V conditions. O I  I  1 ( O  ) CIN _ RMS O V V IN IN
Over Current Protection (OCP)
The sensed low side MOSFET valley current signal is if let m equal the conversion ratio: also used for over current protection. Since the AOZ6762DI employs valley current mode control, during VO over current conditions, it will skip a pulse if the valley ---- = m V current over the OC point setting until the output drop to IN some level after current limit. The AOZ6762DI will shut The relation between the input capacitor RMS current down and auto restart with hiccup mode. To prevent the and voltage conversion ratio is calculated and shown in current running away in the extreme case, the minimum Figure 2 below. It can be seen that when VO is half of VIN, inductor value needed is 2.2µH for the application. CIN it is under the worst current stress. The worst current stress on C
Power-On Reset (POR)
IN is 0.5 x IO. A power-on reset circuit monitors the VIN voltage. When 0.5 the VIN voltage exceeds 4.1V, the converter starts operation. When VIN voltage falls below 3.7V, the 0.4 converter will be shut down. 0.3 I (m) CIN_RMS
Thermal Protection
IO An internal temperature sensor monitors the junction 0.2 temperature. It shuts down the internal control circuit and 0.1 high side NMOS if the junction temperature exceeds 150ºC. The regulator will restart automatically under the 0 control of soft-start circuit when the junction temperature 0 0.5 1 decreases to 100ºC. m
Figure 2. I Application Information CIN vs. Voltage Conversion Ratio
The basic AOZ6762DI application circuit is show in For reliable operation and best performance, the input Figure 1. Component selection is explained below. capacitors must have current rating higher than ICIN-RMS at worst operating conditions. Ceramic capacitors are
Input Capacitor
preferred for input capacitors because of their low ESR and high current rating. Depending on the application The input capacitor must be connected to the VIN pin and circuits, other low ESR tantalum capacitor may also be GND pin of AOZ6762DI to maintain steady input voltage used. When selecting ceramic capacitors, X5R or X7R and filter out the pulsing input current. The voltage rating type dielectric ceramic capacitors should be used for of input capacitor must be greater than maximum input their better temperature and voltage characteristics. Note voltage plus ripple voltage. that the ripple current rating from capacitor manufactures The input ripple voltage can be approximated by are based on certain amount of life time. Further de- equation below: rating may be necessary in practical design. I  V  V
Inductor
V O = --------- O   – ----- O  ----- IN 1   V The inductor is used to supply constant current to output f  CIN IN VIN when it is driven by a switching voltage. For given input and output voltage, inductance and switching frequency Since the input current is discontinuous in a buck together decide the inductor ripple current, which is: converter, the current stress on the input capacitor is another concern when selecting the capacitor. For a buck V  V  I O = ----- O   – ----- L 1  f  L V  IN Rev. 1.0 October 2019
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