CAT4238 High Efficiency 10 LED Boost Converter FEATURES DESCRIPTION Drives High Voltage LED strings (38V) The CAT4238 is a DC/DC step-up converter that delivers an accurate constant current ideal for driving LEDs. Up to 87% Efficiency Operation at a fixed switching frequency of 1MHz allows Low Quiescent Ground Current 0.6mA the device to be used with small value external ceramic Adjustable Output Current capacitors and inductor. LEDs connected in series are 1MHz Fixed Frequency Low noise Operation driven with a regulated current set by the external resistor R1. LED currents up to 40mA can be supported over a Soft start in-rush current limiting wide range of input supply voltages up to 5.5V, making Shutdown current less than 1 A the device ideal for battery-powered applications. The Open LED Overvoltage Protection CAT4238 high-voltage output stage is perfect for driving Automatic Shutdown at 1.9V (UVLO) mid-size and large panel displays containing up to ten white LEDs in series. Thermal overload protection Thin SOT23 5-Lead (1mm max height) LED dimming can be done by using a DC voltage, a logic signal, or a pulse width modulation (PWM) signal. The APPLICATIONS shutdown input pin allows the device to be placed in GPS Navigation Systems power-down mode with zero quiescent current. Portable Media Players In addition to thermal protection and overload current Handheld Devices, Digital Cameras limiting, the device also enters a very low power Portable Game Machines operating mode during Open LED fault conditions. The device is housed in a low profile (1mm max height) 5-lead thin SOT23 package for space critical applications. ORDERING INFORMATION Quantity Package Part Number Package per Reel Marking TSOT23-5 CAT4238TD-GT3 3000 MU Green* * Lead Finish NiPdAu For Ordering Information details, see page 13. TYPICAL APPLICATION CIRCUIT PIN CONFIGURATION LDVOUT TSOT23 5-Lead VIN (1mm max height) 47H C1 C2 SW 1 5 VIN 4.7F 0.22F SW VIN GND 2 CAT4238 (300mV) 3 4 SHDN FB 20mA OFF ON SHDN FB R1 GND 15 Top View L: Sumida CDC5D23B-470 D: Central CMDSH05-4 C2: Taiyo Yuden UMK212BJ224 (rated 50V) Catalyst Semiconductor, Inc. 1 Doc. No. MD-5019 Rev. C Characteristics subject to change without notice CAT4238 ABSOLUTE MAXIMUM RATINGS Parameters Ratings Units VIN, FB voltage -0.3 to +7 V SHDN voltage -0.3 to +7 V (1) SW voltage up to 60 V Storage Temperature Range -65 to +160 C Junction Temperature Range -40 to +150 C Lead Temperature 300 C Note: (1) The SW pin voltage is rated up to 39V for external continuous DC voltage. RECOMMENDED OPERATING CONDITIONS Typical application circuit with external components are shown on page 1. Parameters Range Units VIN up to 5.5 V SW pin voltage 0 to 38 V Ambient Temperature Range -40 to +85 C DC ELECTRICAL CHARACTERISTICS VIN = 3.6V, ambient temperature of 25C (over recommended operating conditions unless specified otherwise). Typ Symbol Parameter Test Conditions Min Max Units I Operating Current V = 0.2V 0.6 1.5 mA Q FB V = 0.4V (not switching) 0.1 0.6 FB I Shutdown Current V = 0V 0.1 1 A SD SHDN V FB Pin Voltage 10 LEDs with I = 20mA 285 300 315 mV FB LED I FB pin input leakage 1 A FB I Programmed LED Current 28.5 30 31.5 mA LED R1 = 10 19 20 21 R1 = 15 14.25 15 15.75 R1 = 20 V SHDN Logic High Enable Threshold Level 0.8 1.5 V IH V SHDN Logic Low Shutdown Threshold Level 0.4 0.7 V IL F Switching Frequency 0.8 1.0 1.3 MHz SW DC Maximum Duty Cycle VIN = 3V 92 % I Switch Current Limit 350 450 600 mA LIM R Switch On Resistance I = 100mA 1.0 2.0 SW SW I Switch Leakage Current Switch Off, V = 5V 1 5 A LEAK SW Thermal Shutdown 150 C Thermal Hysteresis 20 C V Undervoltage Lockout (UVLO) 1.9 V UVLO Threshold V Overvoltage Detection Threshold 40 V OV-SW V Output Voltage Clamp Open LED 42 V OCL Doc. No. MD-5019 Rev. C 2 Catalyst Semiconductor, Inc. Characteristics subject to change without notice