NX2305

Evaluation board available. NX2305 SINGLE SUPPLY 12V SYNCHRONOUS PWM CONTROLLER WITH NMOS LDO CONTROLLER, POWER GOOD & ENABLES PRELIMINARY DATA SHEET Pb Free Product DESCRIPTION 12V PWM controller plus LDO controller The NX2305 controller IC is a combination synchronous Hiccup current limit by sensing Rdson of MOSFET Buck and LDO controller IC designed to convert single 12V high side and low side driver 12V supply to low cost dual on board supply applicaFixed internal 300kHz for switching controller tions. The synchronous controller is used for high curDual Independent Digital Soft Start Function rent high efficiency step down DC to DC converter appliAdaptive Deadband Control cations while the LDO controller in conjunction with an Enable pin available to program the Vbus UVLO external low cost N ch MOSFET can be used as a very Shut Down switching and LDO via pulling down low drop out regulator in applications such as converting EnSW or ENLDO pins 3.3V to 2.5V output. Internal UVLO keeps both regulan Pb-free and RoHS compliant tors off until the supply voltage exceeds 9V where independent internal digital soft starts get initiated to ramp up both outputs.The switching section has hiccup current limit by sensing the Rdson of synchronous MOSFET. n PCI Graphic Card on board converters The LDO controller has Feedback Under Voltage Lock n Mother board On board DC to DC applications Out as a short circuit protection.Other features includes: n On board Single Supply 12V DC to DC such as 12V to 3.3V, 2.5V or 1.8V 12V gate drive capability , Adaptive dead band control, Power good flag for the switcher controller and separate n Set Top Box and LCD Display Enable pins for independent power sequencing. R14 10 C11 open 5V REG PGOOD C9 M5 47uF C10 150pF LDO FB R9 5k HDRV C8 150uF 25mohm R10 ENLDO 0.75k R11 1.4k M3 R8 5k LDO OUT BST C4 0.1uF C12 1uF VCC PVCC C1 0.1uF 1N4148 L1 1uH C2 180uF M1 IRFR3709Z L2 2.2uH C7 2 x 470uF OCP LDRV PGND R1 4k M2 IRFR3709Z R2 1.1k C6 3.9nF ENSW 6.8k R13 1.4k M4 AGND FB R5 COMP 10k 5.6nF C5 R4 8k C3 100uF n n n n n n n n FEATURES APPLICATIONS TYPICAL APPLICATION VIN2 +3.3V VOUT2 +1.6V/2A R6 10k VIN1 +12V NX2305 SW VOUT1 +1.8V/10A VIN2 +3.3V HI=SD VIN1 +12V R3 10k R12 HI=SD C13 100pF Figure1 - Typical application of NX2305 ORDERING INFORMATION Device NX2305CMTR NX2305CSTR Rev.5.0 08/19/08 Temperature 0 to 70oC 0 to 70oC Package MLPQ-16L SOIC -16L Frequency 300kHz 300kHz Pb-Free Yes Yes 1 NX2305 ABSOLUTE MAXIMUM RATINGS Vcc to PGND & BST to SW voltage .................... -0.3V to 16V BST to PGND Voltage ...................................... -0.3V to 35V SW to PGND .................................................... -2V to 35V All other pins .................................................... -0.3V to 6.5V Storage Temperature Range ............................... -65oC to 150oC Operating Junction Temperature Range ............... -40oC to 125oC CAUTION: Stresses above those listed in "ABSOLUTE MAXIMUM RATINGS", may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. PACKAGE INFORMATION 16-LEAD PLASTIC MLPQ COMP OCP BST SW 16-LEAD PLASTIC SOIC θ JA ≈ 46o C/W BST HDRV GND LDRV PVCC VCC LDO-OUT LDO-FB 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 θ JA ≈ 83o C/W SW OCP COMP FB PGOOD EN-SW EN-LDO 5V REG 16 HDRV 1 PGND 2 LDRV 3 PVCC 4 5 VCC 15 14 13 12 FB 17 AGND 11 PGOOD 10 EN-SW 9 EN-LDO 6 LDO-OUT 7 LDO-FB 8 5V REG ELECTRICAL SPECIFICATIONS Unless otherwise specified, these specifications apply over Vcc =12V, V BST-VSW =12V, ENSW=ENLDO=3V, and TA = 0 to 70oC. Typical values refer to TA = 25oC. PARAMETER Reference Voltage Ref Voltage Ref Voltage line regulation Supply Voltage(Vcc&VBST) VCC Voltage Range VCC Supply Current (Static) PVCC Supply Current (Dynamic) VBST Voltage Range VBST Supply Current(Static) SYM VREF 10V2/gm. And it would be desirable if R1||R2||R3>>1/gm can be met at the same time. Zin R3 Vout Zf C1 C2 Fb gm Ve R4 R2 A. Type III compensator design For low ESR output capacitors, typically such as Sanyo oscap and poscap, the frequency of ESR zero caused by output capacitors is higher than the crossover frequency. In this case, it is necessary to compensate the system with type III compensator. The following figures and equations show how to realize the type III compensator by transconductance amplifier. C3 R1 Vref Figure 3 - Type III compensator using transconductance amplifier Rev.5.0 08/19/08 10 NX2305 Case 1: FLC