AP8802HEV2
Issue 1 – August 2010 www.diodes.com
© Diodes Incorporated, 2010
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AP8802HEV2 EVALUATION BOARD
REFERENCE DESIGN
The AP8802HEV2 is an evaluation board configured to be used with the AP8802H in SOP-8L-EP
package. The target application is a driver for one or more series-connected LEDs for luminaires in
both commercial and automotive applications.
The maximum operating voltage for the evaluation board is 60V, and a 0R2 sense resistor R1 sets the
nominal current at 1A.
An accurate way of determining the current, avoiding the need to insert an ammeter in the current
path, is to measure the voltage on the sense resistor. A 10k resistor and a 1uF capacitor can be used
to form a low pass filter and the voltage across the capacitor represents a more stable DC reading of
current. Using this method, 200mV represents 1 Amp when using a 0R2 sense resistor.
The CTRL pin connects to a low pass filter within the AP8802H chip to provide some decoupling, but
the external capacitor C2 (100nF) can be used to provide additional decoupling to reduce any high
frequency noise as well as providing the soft start function.
Both DC and PWM dimming can be achieved by driving the CTRL pin. For DC dimming, the CTRL pin
may be driven between 0.3V and 1.25V. Driving the CTRL pin below 0.2V will shut down the output
current. For PWM dimming, an external open-collector NPN transistor or open-drain N-channel
MOSFET can be used to drive the CTRL pin. The PWM frequency can be around 100Hz to 1 kHz.
For better resolution, PWM capacitor C2 should be removed from the evaluation board, to give a more
accurate duty cycle.
Shorting R2 will connect the test pin CTRL to device pin CTRL if needed. The external capacitor C2
on the CTRL pin sets the soft start time. The amount of soft start time achievable is approximately
0.2ms/nF.
For other reference designs or further applications information, please refer to the AP8802H
datasheet.
Name Description
SW
Switch Pin. Connect inductor/freewheeling diode here. Minimize trace area at this pin to reduce
EMI.
GND GND pin
SET Set Nominal Output Current Pin. Configure the output current of the device.
CTRL
Dimming and On/Off Control Input. Input voltage of 0.2V or lower forces the device into low
current standby mode and shut off the output. A PWM signal allows the output current to be
adjusted above or below the level set by the resistor connected to SET input pin.
The input impedance is about 50k, and if the pin is left open V
CTRL
= V
REF
V
IN
Input Supply Pin. Must be locally bypassed with a capacitor.
NC No connection
