Datasheet

4
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
2.0 Pin Descriptions
Table 2.1 Pin Assignments
Name MSL3080 Pin Description
FB 1
V
LED
Voltage Regulator Feedback Input: Connect a resistive voltage divider from the boost regulator output, V
LED
, to FB to set the un-
optimized boost regulator output voltage. The feedback regulation voltage is 2.5V.
VIN 2 Power Supply Input: Power supply input. Apply 4.5V to 5.5V to VIN. Decouple VIN to GND a 1µF or greater capacitor placed close to VIN.
SDA 3
I²C Serial Data I/O: SDA is the I²C serial interface data input/output. Connect SDA to VIN when unused. For interface information see the
“MSL3040/50/60/80/86/87/88 Programming Guide”.
SCL 4
I²C Serial Clock Input: SCL is the I²C serial interface clock input. Connect SCL to VIN when unused. For interface information see the
“MSL3040/50/60/80/86/87/88 Programming Guide”.
SCTH 5
String Short Circuit Threshold Level Setting Input: SCTH programs the LED string short-circuit detection threshold. Connect a resistor from
SCTH to GND to set the short-circuit threshold level to 4.9V (1kΩ), 5.8V (27kΩ), 6.8V (68kΩ) or 7.6V (330kΩ). A short circuit is detected
when the STRn voltage is above the threshold while STRn is on. See the section “Setting the LED Short-Circuit Threshold” on page 17 for
information.
STR0 6
LED String 0 Current Sink: Connect the cathode end of series LED String 0 to STR0. If not used, connect STR0 to GND.
STR1 7 LED String 1 Current Sink: Connect the cathode end of series LED String 1 to STR1. If not used, connect STR1 to GND.
STR2 8 LED String 2 Current Sink: Connect the cathode end of series LED String 2 to STR2. If not used, connect STR2 to GND.
STR3 9 LED String 3 Current Sink: Connect the cathode end of series LED String 3 to STR3. If not used, connect STR3 to GND.
STR4 10 LED String 4 Current Sink: Connect the cathode end of series LED String 4 to STR4. If not used, connect STR4 to GND.
STR5 11 LED String 5 Current Sink: Connect the cathode end of series LED String 5 to STR5. If not used, connect STR5 to GND.
STR6 12 LED String 6 Current Sink: Connect the cathode end of series LED String 6 to STR6. If not used, connect STR6 to GND.
STR7 13 LED String 7 Current Sink: Connect the cathode end of series LED String 7 to STR7. If not used, connect STR7 to GND.
CGND 15 Connect To Ground: Connect CGND to GND close to the driver.
PWM 14
PWM Dimming and Synchronization Input: Drive PWM with a pulse-width modulated signal with duty cycle of 0% to 100% and frequency of
20Hz to 50kHz to control the duty cycle and the frequency of all LED strings. For serial interface controlled PWM dimming connect PWM to
GND and refer to the register definitions section for registers 0x10 through 0x14 in the “MSL3040/50/60/80/86/87/88 Programming Guide”.
ILED 16
Maximum LED Current Control Input: Connect a resistor from ILED to GND to set the full-scale LED current. See the section “Setting the
LED Current” on page 17 for more information.
PGND 17 Power Ground: Ground of the boost regulator gate driver. Connect PGND to GND, EP and CGND as close to the MSL3080 as possible.
GATE 18 Gate Drive Output: Connect GATE to the gate of the boost regulator switching MOSFET
PVIN 19
Boost Regulator Power Supply Input: PVIN is the power supply input for the external MOSFET gate driver. Apply 4.5V to 5.5V to PVIN.
Decouple PVIN with two 1µF capacitors placed close to PVIN.
FLTB 20
Fault Output: FLTB sinks current to GND when a fault is detected. Clear faults by toggling EN low and then high, by cycling input power off
and on, or through the I
2
C serial interface; see the “MSL3040/50/60/80/86/87/88 Programming Guide” for information.
EN 21
Enable Input: Drive EN high to turn on the device, drive it low to turn it off. For automatic startup connect EN to VIN. Toggle EN low then high
to reset FLTB, or reset it through the I2C serial interface.
CS 22
Boost Regulator Current Sense Input: Connect the current sense resistor from CS and the MOSFET source to GND to set the boost regulator
current limit. The current limit threshold is 100mV. See the section “Setting the External MOSFET Current Limit” beginning on page 21 for
more
COMP 23
Boost Regulator Compensation Node: Connect the compensation network components from COMP to FB to compensate the boost regulator
control loop, as shown in the Typical Applications Circuit on page 10. See the section “Loop Compensation” beginning on page 21 for more
information.
GND 24 Signal Ground: Connect GND to EP, PGND and CGND as close to the device as possible.
EP EP
Exposed Die-Attach Paddle: Connect EP to GND, CGND, PGND and to the system ground. EP is the return path for the LED current as well
as the primary thermal path to remove heat generated in the MSL3080. Use a large circuit board trace to connect from EP to the boost supply
output capacitor ground and to the input supply ground return. Connect EP to a large copper ground plane for best thermal and electrical
performance.