Specifications
Rev. 1.0 January 2012
www.aosmd.com
Page 4 of 4
AOZ197
8
Pin Functions
Pin1: VIN
This is the input supply for the controller IC; it is also
the voltage drive for the Gates and DPWM drivers. If
the input power of the boost converter is less than
18V, VIN can be connected directly to the boost
supply voltage. If the boost supply voltage is higher
than 18V, a separate supply rail between 8V and 18V
is required for the VIN pin. It is recommended that an
RC filter should be added between VIN and Boost
supply if they are connected directly.
PIN 2: DPWM1
This is the driver output for the gate of the LED
current control NMOS switch for channel 1. DPWM1 =
LOW if Pin 7 DBRT1 signal is low or fault condition is
triggered. The DPWM1 = HIGH if DBRT1 is high
under normal operating conditions. The high voltage
at DPWM1 equals to Pin1 VIN voltage. It is
recommended to add 1Ω resistor between this pin and
NMOS gate. The resistor value can be optimized
depending on the LED current and selection of
NMOS. DPWM1 can be driven simultaneously with
DPWM2 or independently from DPWM2.
Pin 3: GATE1
This is the driver output for the gate of boost NMOS
switch for channel 1. The GATE = HIGH voltage is
equal to VIN voltage. It is recommended to add a 1Ω
resistor between this pin and the NMOS gate. The
resistor value can be optimized depending on the
selection of NMOS switch. To reduce system noise
and input ripple current, GATE1 is 180⁰ out of phased
from GATE2.
Pins 4, 17: GND
These are the common ground for the IC controller. It
is recommended that all the low current paths are
connected to these pins as close as possible to the IC
controller. It is not recommended to connect any
output or input filter capacitors and any current sense
resistors to these pins directly. The IC controller
ground should be an island around the IC connected
to the PWR GND at a single point in the layout.
Pin 5: COMP1
This is for feedback loop compensation for Channel 1.
It is the output of the error amplifier that controls PWM
logic for the boost controller. An RC network should
be connected to GND to generate the compensation
for boost 1 feedback loop.
Pin 6: OVP1
This is the input for LED Over-Voltage Protection.
OVP1 monitors Channel 1 LED output voltage through
a resistor divider. When the voltage at this pin is
higher than 1V, Channel 1 will immediately stop
switching for 40ms and Pin 20 (FLAG) is instantly
asserted HIGH, indicating a Fault condition, CH1
controller will reset and restart again after 40ms. If
fault condition persists it will repeat until fault condition
is removed.
Pin 7: DBRT1
This is the input for digital brightness control for CH1.
A PWM logic signal is applied to this pin to vary the
brightness of the LED. The brightness of the LED is
proportional to the duty cycle of the PWM logic signal.
The input signal will control the output driver at
DPWM1 pin. This input pin cannot be left floating.
Pin 8: CS1
This is the input for peak current sense for CH1. This
pin serves the functions of current feedback, peak
current limit detection and fault current detection. The
pin current limit is internally set to 0.4V for peak
current limit and 0.48V for fault current detection,
under fault current detection, CH2 controller will assert
FLAG, shutdown and reset every 40ms.
Pin 9: FB1
This is the feedback input for boost controller for CH1.
This pin should connect to a resistor that senses the
LED current. The FB1 voltage will be regulated to Pin
10 (ISET) voltage. If the voltage at FB1 pin exceeds
1V due to a fault condition CH1 controller will reset
and start again after 40ms, if fault condition persists it
will repeat until fault condition is removed.
Pin 10: ISET
This is 0.5V output of the internal reference voltage of
the error Amp for both CH1 and CH2. This pin is
bidirectional; if desired it can be driven externally to
track an external reference or also can be used as a
linear dimming input from 0V to 0.8V, a 10nF or higher
value capacitor to GND must be connected to this pin.
Pin 11: SCP
Short Circuit Protection pin, the rising threshold at this
Pin is 1.14V and falling threshold is 0.96V, if the pin
voltage falls below 0.96V, FLAG will be asserted
HIGH and both channels will shut down and reset
every 40ms, if no current sense resistor this pin can
be used as a typical UVLO pin.