NCP5007
http://onsemi.com
3
PIN FUNCTION DESCRIPTION
Pin Symbol Type Description
1 FB ANALOG
INPUT
This pin provides the output current range adjustment by means of a sense resistor connected
to the analog control or with a PWM control. The dimming function can be achieved by applying
a PWM voltage technique to this pin (see Figure 29). The current output tolerance depends
upon the accuracy of this resistor. Using a "5% metal film resistor, or better, yields good output
current accuracy. Note: A built−in comparator switches OFF the DC−DC converter if the voltage
sensed across this pin and ground is higher than 700 mV typical.
2 GND POWER This pin is the system ground for the NCP5007 and carries both the power and the analog
signals. High quality ground must be provided to avoid spikes and/or uncontrolled operation.
Care must be observed to avoid high−density current flow in a limited PCB copper track so a
robust ground plane connection is recommended.
3 EN DIGITAL
INPUT
This is an Active−High logic input which enables the boost converter. The built−in pulldown
resistor disables the device when the EN pin is left open. Note the logic switching level of this
input has been optimized to allow it to be driven from standard or 1.8 V CMOS logic levels.
The LED brightness can be controlled by applying a pulse width modulated signal to the enable
pin (see Figure 30).
4 V
out
POWER This pin is the power side of the external inductor and must be connected to the external
Schottky diode. It provides the output current to the load. Since the boost converter operates in
a current loop mode, the output voltage can range up to +22 V but shall not exceed this limit.
However, if the voltage on this pin is higher than the OVP threshold (Over Voltage Protection)
the device enters a shutdown mode. To restart the chip, one must either apply a low to high logic
signal to the EN pin, or switch off the V
bat
supply.
A capacitor must be used on V
out
to avoid false triggering of the OVP (Overvoltage Protect)
circuit. This capacitor filters the noise created by the fast switching transients. In order to limit
the inrush current and still have acceptable startup time the capacitor value should range
between 1.0 mF and 8.2 mF max. To achieve high efficiency this capacitor should be ceramic
(ESR t 100 mW).
Care must be observed to avoid EMI through the PCB copper tracks connected to this pin.
5 V
bat
POWER The external voltage supply is connected to this pin. A high quality reservoir capacitor must be
connected across pin 5 and Ground to achieve the specified output voltage parameters. A
4.7 mF/6.3 V, low ESR capacitor must be connected as close as possible across pin 5 and
ground pin 2. The X5R or X7R ceramic MURATA types are recommended.
The return side of the external inductor shall be connected to this pin. Typical application will
use a 22 mH, size 1210, to handle the 10 to 100 mA output current range. When the desired
output current is above 20 mA, the inductor shall have an ESR v1.5 W to achieve good
efficiency over the V
bat
range. The output current tolerance can be improved by using a larger
inductor value.
