CX4060

CX4060 SICORE | Alldatasheet

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Technical content

1 Si-Core Corp. Rev. 1.02 CX4060 PWM Control 2A Step-Down Converter

FEATURES

 2A Output Current  Up to 95% Efficiency  4.75V to 18V Input Range 20µA Shutdown Supply Current 360kHz Switching Frequency  Adjustable Output Voltage from 1.22V to 0.85·VIN Cycle-by-Cycle Current Limit Protection Thermal Shutdown Protection  Frequency Fold Back at Short Circuit Stability with Wide Range of Capacitors,  SOP-8 Package

APPLICATIONS

 TFT LCD Monitors  Portable DVDs  Car-Powered or Battery-Powered Equipments  Set-Top Boxes Telecom Power Supplies  DSL and Cable Modems and Routers Termination Supplies GENERAL DESCRIPTION The CX4060 is a current-mode step-down DC-DC converter that generates up to 2A output current at 360kHz switching frequency. The device utilizes advanced BCD process fo r operation with input voltage up to 18 V consuming only 20µA in shutdown mode, the CX4060 is highly efficient with peak efficienc y at 95% when in operation. Protection features include cycle-by-cycle current limit, thermal shutdown, and frequency fold back at short circuit. The CX4060 is available in SOP-8 package and requires very few external devices for operation. CX4060 G ACT4060 FB COMP SW EN 4.75V to 18V ENABLE IN BS 2.5V/2A EN CX4060 SW FB COMPGnd Figure 1. Typical Application Circuit

2 Si-Core Corp. Rev. 1.02 CX4060

ORDERING INFORMATION

PART NUMBER TEMPERATURE RANGE PACKAGE PINS CX4060 -40°C to 85°C SOP-8 7,1 N/C PIN CONFIGURATION PIN No. PIN NAME PIN DESCRIPTION 1 BS Bootstrap. This pin acts as the positive rail for the high-side switch’s gate driver. Connect a 10nF between this pin and SW. 2 IN Input Supply. Bypass this pin to G with a low ESR capacitor. See Input Capacitor in Application Information section. 3 SW Switch Output. Connect this pin to the switching end of the inductor. 4 G Ground. 5 FB Feedback Input. The voltage at this pin is regulated to 1.22V. Connect to the resistor divider between output and ground to set output voltage. 6 COMP Compensation Pin. See Compensation Technique in Application Information section. Output voltage is discharged when the IC is off. This pin has a small internal pull up current to a high level voltage when pin is not connected. 8 N/C Not Connected. 81BS IN SW GND Com EN N/C CX4060 FB

3 Si-Core Corp. Rev. 1.02 CX4060 ABSOLUTE MAXIMUM RATINGS (Note: Do not exceed these limits to prevent damage to the device. Exposure to absolute maximum rating conditions for long periods may affect device reliability.) PARAMETER VALUE UNIT IN Supply Voltage -0.3 to 20 V SW Voltage -1 to VIN + 1 V BS Voltage VSW - 0.3 to VSW + 6 V EN, FB, COMP Voltage -0.3 to 6 V Continuous SW Current Internally limited A Junction to Ambient Thermal Resistance (¦ÈJA) 105 °C/W Operating Junction Temperature -40 to 150 °C Storage Temperature -55 to 150 °C Lead Temperature (Soldering, 10 sec) 300 °C ELECTRICAL CHARCXERISTICS (VIN = 12V, TJ = 25°C unless otherwise specified) PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT High-Side Switch On Resistance RONH 0.22 Ω Low-Side Switch On Resistance RONL 4.7 Ω SW Leakage VEN = 0 1 10 µA Current Limit ILIM 2.6 3.3 A COMP to Current Limit Transconductance GCOMP 1.8 A/V Error Amplifier Transconductance GEA ∆ICOMP = ±10µA 550 µA/V Error Amplifier DC Gain AVEA 3200 V/V Switching Frequency fSW 300 360 420 kHz Short Circuit Switching Frequency VFB = 0 50 kHz Maximum Duty Cycle DMAX VFB = 1.1V 90 % Minimum Duty Cycle VFB = 1.4V 0% Enable Threshold Voltage Hysteresis = 0.1V 2.0 2.2 V Enable Pull Up Current Pin pulled up to 4.5V typically when left unconnected 2.5 µA Supply Current in Shutdown VEN = 0 20 50 µA IC Supply Current in Operation VEN = 3V, VFB = 1.4V 1.0 1.5 mA Thermal Shutdown Temperature Hysteresis = 10°C 168 °C

4 Si-Core Corp. Rev. 1.02 CX4060 Figure 2 . Functional Block Diagram FUNCTIONAL DESCRIPTION As seen in Figure 2, Functional Block Diagram, the CX4060 is a current mode pulse width modulation (PWM) converter. The converter operates as follows: A switching cycle starts when the rising edge of the Oscillator clock output causes the High-Side Power Switch to turn on and the Low-Side Power Switch to turn off. With the SW side of the inductor now connected to IN, the inductor current ramps up to store energy in the its magnetic field. The inductor current level is measured by the Current Sense Amplifier and added to the Oscillator ramp signal. If the resulting summation is higher than the COMP voltage, the output of the PWM Comparator goes high. When this happens or when Oscillator clock output goes low, the High-Side Power Switch turns off and the Low-Side Power Switch turns on. At this point, the SW side of the inductor swings to a diode voltage below ground, causing the inductor current to decrease and magnetic energy to be transferred to output. This state continues until the cycle starts again. The High-Side Power Switch is driven by logic using BS bootstrap pin as the positive rail. This pin is charged to V SW + 6V when the Low-Side Power Switch turns on. The COMP voltage is the integration of the error between FB input and the internal 1.22V reference. If FB is lower than the reference voltage, COMP tends to go higher to increase current to the output. Current limit happens when COMP reaches its maximum clam value of 2.55V. The Oscillator normally switches at 360kHz. However, if FB voltage is less than 0.7V, then the switching frequency decreases until it reaches a minimum of 50kHz at VFB = 0.5V. SHUTDOWN CONTROL The CX4060 has an enable input EN for turning the IC on or off. When EN is less than 1.8V, the IC is in 20µA low current shutdown mode and output is discharged through the Low-Side Power Switch. When EN is higher than 2.0V, the IC is in normal opera tion mode. EN is internally pulled up with a 2.5µA current source and can be left unconnected for always-on operation. Note that EN is a low voltage input with a maximum voltage of 6V; it should never be directly connected to IN. THERMAL SHUTDOWN The CX4060 automatically turns off when its junction temperature exceeds 168°C. 1.22V

Figure 4. stability compensation but limit RCOMP to 15kΩ maximum. PCB layout parasitic effects. based on the compensation method above. Table 2. Typical Compensation for Different Output

7 Si-Core Corp. Rev. 1.02 CX4060 Typical Application 3.3V/2A Output Typical Application 5.0V/2A Output 10uF/35V 22nF 4.75V to 18V ACT4060 IN EN 5V/2A BS FB COMP SW ENABLE G 15K 10K D1 31K CX4060 10nF L1 22uH/3A 22uF/10V ceramic,or 47uF/6.3 SP cap (optional) IN 10uF/35V 22nF 4.75V to 18V ACT4060 IN EN 3.3V/2A BS FB COMP SW ENABLE G 15K 10K D1 16.9K CX4060 10nF L1 15uH/3A 22uF/10V ceramic,or 47uF/6.3 SP cap (optional) IN Figure5B: CX4060 5V/2A Output Application Figure5A: CX4060 3.3V/2A Output Application

8 Si-Core Corp. Rev. 1.02 CX4060 Typical Application 2.5V/2A Output 10uF/35V 22nF 4.75V to 18V ACT4060 IN EN 2.5V/2A BS FB COMP SW ENABLE G 15K 10K D1 10.5K IC1 CX4060 10nF L1 10uH/3A 22uF/10V ceramic,or 47uF/6.3 SP cap (optional) IN Figure5C: CX4060 2.5V/2A Output Application 10uF/35V 22nF 4.75V to 18V IN EN 2.5V/2A BS FB COMP SW ENABLE G 15K 10K D1 10.5K CX4060 10nF L1 10uH/3A 22uF/10V ceramic,or 47uF/6.3 SP cap (optional) IN 4 6 Figure5C: CX4060 2.5V/2A Output Application TYPECIAL PERFORMANCE AND CHARACTERISTICS:

9 Si-Core Corp. Rev. 1.02 CX4060 PACKAGE OUTLINE SOP-8 PACKAGE OUTLINE AND DIMENSIONS DIMENSION IN MILIMETERS DIMENSION IN INCHES SYMBOL MIN MAX MIN MAX A 1.350 1.750 0.053 0.069 A1 0.100 0.250 0.004 0.010 A2 1.350 1.550 0.053 0.061 B 0.330 0.510 0.013 0.020 C 0.190 0.250 0.007 0.010 D 4.780 5.000 0.188 0.197 E 3.800 4.000 0.150 0.157 E1 5.800 6.300 0.228 0.248 e 1.270 TYP 0.050 TYP L 0.400 1.270 0.016 0.050 ¦È 0° 8° 0° 8° Figure10: Figure11: