IS31LT3554 BOOST TYPE LED DRIVER WITH 4-CHANNEL CURRENT SOURCE August 2015 GENERAL DESCRIPTION FEATURES The IS31LT3554 is a LED driver based on a highly Input voltage range: 4.5V to 33V efficient boost controller operating over a wide input 180mA per string 4-Channel LED current sinks, voltage range of 4.5V to 33V. LED current adjustable from 20mA to 180mA The IS31LT3554 contains four regulated current String-to-string current matching accuracy: 1.5% sources with 1.5% (Typ.) current matching between Adjustable operating frequency: 100kHz to 1MHz strings for a uniform LED brightness. Each current External PWM dimming source can be programmed via an external resistor to High contrast ratio drive from 20mA to 180mA. A fast slew rate current Less than 3A shutdown current source allows high frequency and narrow pulse width Programmable soft-start dimming signals to achieve a very high contrast ratio. Built-in protection features The device operating frequency can be adjusted from - OCP, OTP, UVLO 0.1MHz to 1MHz. - Open/short LED protection The IS31LT3554 has safety protection features to - Programmable OVP prevent damage during fault conditions. Protection - Schottky Diode/inductor short-circuit protection features include an internal soft-start circuit to prevent a high inrush current during startup, open/short LED protection to automatically disable a faulty current APPLICATIONS source, over temperature protection (OTP), cycle-by-cycle current limit, under voltage lockout LCD Monitor/TV (UVLO), programmable OVP, VOUT short / Schottky LED lighting diode open protection and Schottky Diode short-circuit protection. The IS31LT3554 is available in a thermally enhanced eTSSOP-16 package. TYPICAL APPLICATION CIRCUIT Figure 1 Typical Application Circuit Integrated Silicon Solution, Inc. www.issi.com 1 Rev. A, 08/18/2015 IS31LT3554 PIN CONFIGURATION Package Pin Configuration (Top View) eTSSOP-16 PIN DESCRIPTION No. Pin Description 1 RT A resistor value to ground sets the switching frequency from 100kHz to 1MHz. Enable Input. The IC is Enabled when this pin is above 2.4V. The IC is Disabled 2 EN and in Shutdown mode when this pin is below 0.5V. In shutdown mode only a minimal 3A current is consumed. Current Sense Input from the switching converter. A sense resistor from the 3 CS source of the external N-MOSFET to GND sets the switching current limit. Switching N-MOSFET Gate Drive Output. This pin outputs a high voltage 4 OUT (5V/V -0.5V) to drive an external switching N-MOSFET. CC 5V linear regulator output. Bypass this pin to GND with a ceramic capacitor as 5 VCC close as possible to the pin. Supply input (4.5V to 33V). Bypass VIN to GND with a capacitor (typical 10F) 6 VIN to keep the DC input voltage constant. 7 STATUS LED operation status will output logic low if a fault is detected. 8 COMP Soft-start and control loop compensation. PWM signal input for LED dimming. If dimming is not implemented, connect it 9 DIM to VCC pin 5. LED current sink 1 and 2 (up to 180mA). If unused leave the pin open 10,11 CH1,CH2 unconnected. 12 GND Ground. Connect all grounds at a single point. LED current sink 3 and 4 (up to 180mA). If unused leave the pin open 13,14 CH3,CH4 unconnected. LED Current Adjust Input. Connect a resistor R between ISET pin and GND ISET 15 ISET to set the reference current through each LED string. Over Voltage Protection pin. Connect a resistor-divider from the switching converter output to this pin. The OVP comparator reference is internally set to 16 OVP 2.0V. Above 2.0V triggers OVP and shuts down switch power switch resumes normal operation when the pin voltage drops below hysteresis voltage. Thermal Pad Connect to GND. Integrated Silicon Solution, Inc. www.issi.com 2 Rev. A, 08/18/2015