IRU3138

Data Sheet No. PD94701 IRU3138 SYNCHRONOUS PWM CONTROLLER FOR TERMINATION POWER SUPPLY APPLICATIONS FEATURES 1A Peak Output Drive Capability 0.8V Precision Reference Voltage Available Shuts off both drivers at shorted output and shutdown 200KHz to 400KHz operation set by an external resistor Soft-Start Function Uncommitted Error Amplifier available for DDR voltage tracking application Protects the output when control FET is shorted Synchronous Controller in 14-Pin Package DESCRIPTION The IRU3138 controller IC is designed to provide a low cost synchronous Buck regulator for voltage tracking applications such DDR memory and general purpose on-board DC to DC converter. Modern micro processors combined with DDR memory, need high-speed bandwidth data bus which requires a particular bus termination voltage. This voltage will be tightly regulated to track the half of chipset voltage for best performance. The IRU3138 together with two N-channel MOSFETs, provide a low cost solution for such applications. This device features a programmable frequency set from 200KHz to 400KHz, under-voltage lockout for both Vcc and Vc supplies, an external programmable soft-start function as well as output under-voltage detection that latches off the device when an output short is detected. APPLICATIONS DDR memory source sink Vtt application Graphic Card Low cost on-board DC to DC such as 5V to 3.3V, 2.5V or 1.8V TYPICAL APPLICATION 5V VDDQ (2.5V) C1 0.1uF 12V C2 1uF C3 2x 47uF L1 1uH C4 47uF DDR Memory R1 1K Vcc VREF VP Vc HDrv Q1 IRF7460 D1 BAT54 L2 3.3uH R2 1K SS/SD C5 0.1uF U1 IRU3138 LDrv PGnd Fb Vtt 1.25V @ 10A C6 2x 150uF 40m V Q2 IRF7456 Rt Comp C7 3300pF R3 13K Gnd Figure 1 - Typical application of IRU3138 when VTT tracks the VDDQ. PACKAGE ORDER INFORMATION TA (°C) 0 To 70 DEVICE IRU3138CS PACKAGE 14-Pin Plastic SOIC NB (S) Rev. 1.0 01/29/04 www.irf.com 1 IRU3138 ABSOLUTE MAXIMUM RATINGS VCC Supply Voltage .................................................. -0.5V - 25V VC Supply Voltage .................................................... -0.5V - 25V Storage Temperature Range ...................................... -65°C To 150°C Operating Junction Temperature Range ..................... 0°C To 125°C CAUTION: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. PACKAGE INFORMATION 14-PIN PLASTIC SOIC NB (S) Fb 1 VP 2 V REF 3 Vcc 4 NC 5 LDrv 6 Gnd 7 14 NC 13 SS/SD 12 Comp 11 Rt 10 Vc 9 HDrv 8 PGnd uJA=888C/W ELECTRICAL SPECIFICATIONS Unless otherwise specified, these specifications apply over V CC=5V, VC=12V and TA=0 to 70°C. Typical values refer to TA=25°C. Low duty cycle pulse testing is used which keeps junction and case temperatures equal to the ambient temperature. PARAMETER Reference Voltage VREF Voltage Fb Voltage Line Regulation UVLO UVLO Threshold - VCC UVLO Hysteresis - VCC UVLO Threshold - VC UVLO Hysteresis - VC UVLO Threshold - Fb UVLO Hysteresis - Fb Supply Current VCC Dynamic Supply Current VC Dynamic Supply Current VCC Static Supply Current VC Static Supply Current Soft-Start Section Charge Current Oscillator Frequency Ramp Amplitude SYM V FB LREG TEST CONDITION MIN 0.784 TYP 0.8 MAX 0.816 1.6 4.5 3.65 0.5 UNITS V mV V V V V V V mA mA mA mA mA KHz V Rev. 1.0 01/29/04 5