ncp5050 ON Semiconductor, ncp5050 Datasheet - Page 3

• Manufacturer Part Number: ncp5050
• Description: 4.5 W Inductive Boost Led Driver For Flash And Lcd Backlight
• Manufacturer: ON Semiconductor

PIN FUNCTION DESCRIPTION
Pin
10
1
2
3
4
5
6
7
8
9
PGND
Name
CTRL
PVIN
PCA
HCS
LCS
SW
Pin
CM
VS
FB
POWER
POWER
INPUT
INPUT
INPUT
INPUT
INPUT
INPUT
INPUT
INPUT
Type
Power Ground: This pin is the power ground and carries the high switching current. A high quality
ground must be provided to avoid any noise spikes/uncontrolled operation. Cares must be observed to
avoid high-density current flow in a limited PCB copper track.
Voltage Sense: In order to sense V
connected to the output bypass capacitor C
Control and Enable: An active high logic level on this pin enables the device. A built-in pulldown
resistor disables the device if the pin is left open. Also in disable condition the device provide a true
cut-off thank to the high impedance on FB input. This pin can also be used to control the average
current into the load by applying a low frequency PWM signal. If a PWM signal is applied, the
frequency should be high enough to avoid optical flicker but be no greater than 50 kHz.
Current Mode: An active high logic on this input enables the High Current Sense used for flash and
disables the LCS resistor. This pin has a low voltage threshold so it can be driven directly from 1.8 V
logic signals. If this function is not needed, this pin should be grounded. Only when CM pin is high, a
safety function switch off the output if CTRL pin is high longer than 1.2 s
Peak Current Adjust: A resistor between this input and ground controls the maximum peak current
allowed in the inductor. The minimum value for this resistor is 2.8 kW and increasing this value
decreases the peak current. This allows the user to adjust the current based on the application needs
and scale the size of the inductor accordingly. See “Switch Current Limit” guidelines in application
section.
High Current Sense: This pin is used for Flash Mode. If the user desires two levels of LED current
then a resistor should be connected from this pin to ground. This function is controlled by the CM input.
Feedback: The reference is 250 mV. This pin provides the feedback voltage by means of the sense
resistors fixed by LCS or HCS pin. When the device is enables and CM low, the LCS resistor is
connected to this pin, thereby the LCS setup the LED current. The tolerance of the LED current is
dependant upon the accuracy of this sense resistor and a $1% metal film resistor, or better, is
recommended for best output accuracy.
Low Current Sense: This pin is used for Torch Mode. In order to fix the current when CM logic pin is
low, a resistor should be connected from this pin to ground.
Power Supply: The external voltage supply is connected to this pin. A 4.7 mF / 6.3 V high quality
capacitor must be connected across this pin and the power ground to achieve the specified output
power parameters. The X5R low DC/C versus DC bias ceramic types are highly recommended.
Switch: Power switch connection for inductor. Typical application will use a coil from 2.2 mH - 4.7 mH
and must be capable of handling the peak current.
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NCP5050
3
out
notably for over voltage protection, this input must be
out
Description
.