NCP5008, NCP5009
http://onsemi.com
3
PIN FUNCTION DESCRIPTION
Pin Symbol Type Description
1 I
ref
INPUT This pin provides the output current range adjustment by means of a resistor connected to
ground. The current output tolerance depends upon the accuracy of this resistor. Using a "1%
metal film resistor, or better, yields the best output current accuracy.
2 PHOTO SIGNAL This pin provides an access to the output current control loop for the NCP5009 version. The cur-
rent sunk to ground from this pin is subtracted from the output current mirror. Primary use is the
ambient light automatic adjustment by means of an external photo transistor connected across
this pin and ground. The output current decreases as the ambient light increases. The internal
circuit provides a 1/1 current ratio with the I
ref
defined by the resistor connected from pin 1 to
ground. This current shall be limited to 65 mA.
This functionality is NOT implemented on the NCP5008 type.
3 CS INPUT Negative going Chip Select logic input. This pin is used to select the NCP5008/ NCP5009 and
validate the clock/data when CS = Low. The internal shift register is automatically clear to zero
upon the falling edge, thanks to a 20 ns built−in one shoot. The built−in pull−up resistor disables
the device when the CS pin is left open.
4 VBIAS POWER This pin should be connected to V
bat
.
5 CLOCK INPUT The clock signal connected to this pin is used to serially shift right the internal preset high logic
level. The clock is valid between the falling edge and until the rising edge of the CS. There is nei-
ther a feedback nor an overflow control. If the clock count exceeds 8 bits, the internal register is
clear, the output current is forced to zero and the device comes back to the shutdown mode.
6 LOCAL INPUT This pin is used to select the mode of operation.
• When LOCAL = High or Open, the chip is controlled by two digital lines:CS and CLOCK. The
output current is programmed by the logic control of these pins, allowing a current adjustment
within the range defined by the I
ref
resistor.
• When LOCAL = Low, the chip is turned ON /OFF by means of the CS line, the CLOCK pins
being deactivated. The output current is constant, as defined by the I
ref
resistor value.
In order to minimize the standby current a dynamic pull−up resistor is activated when POR is
High, this pull−up resistor being disconnected when LOCAL = Low.
7 GND POWER This pin is the system ground for the NCP5008/NCP5009 and carries both the Power and the
Digital signals. High quality ground must be provided to avoid spikes and/or uncontrolled opera-
tion. Care must be observed to avoid high−density current flow in a limited PCB copper track.
8 L2 POWER This pin is the power side of the external inductor and must be connected either to the external
Schottky diode (see Figure 22) or directly to one external LED (see Figure 23). 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 +15 V but shall not extend this limit. The user must make sure this voltage
will not be exceeded during the normal operation of this part.
An external low cost ceramic capacitor (2.2 mF/16 V, ESR < 100 mW) is recommended to smooth
the current flowing into the diode(s), thus limiting the noise created by the fast transients present
in this circuitry.
Care must be observed to avoid EMI though the PCB copper tracks connected to this pin.
9 L1 POWER 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 2.8 to 364 mA max range. On the other hand, when the desired
output current is above 20 mA, the inductor shall have an ESR < 1.0 W. The output current toler-
ance can be improved by using a larger inductor value.
10 V
bat
POWER The external voltage supply is connected to this pin. A high quality reservoir capacitor must be
connected across pin 10 and Ground to achieve the specified output voltage parameters. A
10 mF/6.3 V, low ESR capacitor must be connected as close as possible across pin 10 and
ground pin 7. The X5R ceramic types are recommended.
