Datasheet NCP51460 (ON Semiconductor) - 10

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NCP51460
A 0.1 mF or larger input capacitor will help to decrease the can be slightly different and should be confirmed in the end dv/dt of the input voltage and improve stability during large application. load current changes. No external voltage source should be connected directly During the Turn−On for certain conditions the output to the VOUT pin of NCP51460 regulator. If the external voltage can exhibit an overshoot. The amount of the source forces the output voltage to be greater than the overshoot strongly depends on application conditions i.e. nominal output voltage level, the current will start to flow input voltage level, slew rate, input and output capacitors, from the Voltage Source to the VOUT pin. This current will and output current. The maximum value of the overshoot increase with the Output Voltage applied and can cause isn’t guaranteed for this device. damage to the device if VOUT > 10 V Typ. at 25°C The figure below shows an example of the Turn−On (Figure 30). overshoot. 24 20 COUT = 0 mF, TAGE T 6 A = 25°C PIN (mA) 4 16 OUT 2 (2 V/DIV) O V 0 12 , INPUT VOL V IN - 8 T 3 4 2 VIN = 0 V to 6 V, CURRENT INT I O 1 COUT = 0 mF, I 0 OUT = 1 mA, TA = 25°C, OUTPUT VOL 0 3 4 5 6 7 8 9 10 AGE (1 V/DIV) trise = 30 ms VOUT, OUTPUT VOLTAGE (V) V OUT TIME (10 ms/DIV)
Figure 30. Figure 29. Output Noise Turn−Off Response
The NCP51460 Output Voltage Noise strongly depends The Turn−Off response time is directly proportional to the on the output capacitor value and load value. This is caused output capacitor value and inversely proportional to the load by the fact that the bandwidth of the Reference is inversely value. proportional to the capacitor value and directly proportional The NCP51460 device does not have any dedicated to the output current. The Reference bandwidth directly internal circuitry to discharge the output capacitor when the determines the point where the output voltage noise starts to input voltage is turned−off or disconnected. This is why fall. This can be observed at the Figure 31 below. when large output capacitors are used and very small output current is drawn, it can take a considerable amount of time 2.2 to discharge the capacitor. If short turn−off times are /rtHz) 2.0 V s IN = 5.8 V required, the output capacitor value should be minimized i.e. I 1.8 OUT = 0 mA, with no output capacitor a 20 ms turn−off time can be mV rm COUT = 0 − 10 mF MLCC, 1.6 TA = 25°C C achieved. OUT = 0.1 mF 1.4 COUT = 1.0 mF
Protection Features
1.2 The NCP51460 device is equipped with reverse input 1.0 voltage protection which will help to protect the device TAGE NOISE ( 0.8 COUT = 10 mF when Input voltage polarity is reversed. In this circumstance 0.6 C the Input current will be minimized to typically less than OUT = 0 mF 0.4 0.1 mA. The short circuit protection will protect the device under 0.2 , OUTPUT VOL the condition that the V 0.0 OUT is suddenly shorted to ground. V n 10 100 1000 10k 100k 1M The short circuit protection will work properly up to an Input f, FREQUENCY (Hz) Voltage of 27 V at TA = 25°C. Depending on the PCB trace
Figure 31.
width and thickness, air flow and process spread this value
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