NX2423
TWO PHASE SYNCHRONOUS PWM CONTROLLER WITH INTEGRATED FET DRIVER, DIFFERENTIAL CURRENT SENSE & 5V BIAS REGULATOR
PRELIMINARY DATA SHEET Pb Free Product The NX2423 is a two-phase PWM controller with inte- n Differential inductor DCR sensing eliminates the problem with layout parasitic grated FET driver designed for low voltage high current n 5V bias regulator available application. The two phase synchronous buck converter offers ripple cancelation for both input and output. The n Low Impedance On-board Drivers NX2423 uses differential remote sensing using either cur- n Hiccup current limit and IOUT indication rent sense resistor or inductor DCR sensing to achieve n Power Good for power sequencing accurate current matching between the two channels. n EN2_B pin allows the slave channel on and off while the master channel is working Differential sensing eliminates the error caused by PCB n Programmable frequency board trace resistance that otherwise presents when usn Prebias start up ing a single ended voltage sensing. In addition the NX2423 offers high drive current capabil- n OVP without negative spike at output ity especially for keeping the synchronous MOSFET off n Selectable between internal and external reference during SW node transition, can provide regulated 5V to n Internal Schottky diode from PVCC to BST IC biasing and drivers via 5V bias regulator, allows the n Pb-free and RoHS compliant slave channel on and off via EN2_B pin while the main channel is working. Other features: PGOOD output, pro- n Graphic card High Current Vcore Supply grammable switching frequency and hiccup current lim- n High Current on board DC to DC converter iting circuitry. applications
12V BUS
R10
2N3904
DESCRIPTION
FEATURES
APPLICATIONS
TYPICAL APPLICATION
C11 C10
VCCDRV
2N3904
BST1 C12 HDRV1 SW1 Q1 L1
5V
R13 R14
VOUT
C13 Q2 R29 C15 C14
C31 R11 C30
PVCC
LDRV1
5VCC REFIN AGND CSCOMP
R16 R17 C28 CS+1 R28
NX2423
CS-1
R15
C29
C17 BST2 C19 HDRV2 SW2 Q3
C18
RT IOUT/IMAX
C27 R18 C26
L2 R27 C20 C21
VCOMP
R19 C25 LDRV2 Q4
C22
FB
R20
EN2_B
CS+2 CS-2 R24
R26
VOUT
PGND(PAD)
INREFOUT/POK
C24
Ref for external circuitry
Figure1 - Typical application of NX2423
ORDERING INFORMATION
Device NX2423CMTR
Rev. 2.1 12/01/08
Temperature 0 to 70oC
Package MLPQ 4x4 - 24L
Frequency 50kHz to 1MHz
Pb-Free Yes 1
NX2423
ABSOLUTE MAXIMUM RATINGS
Vcc to PGND & BST to SW voltage .................... -0.3V to 6.5V 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 Lead temperature(Soldering 5s) ........................... 260oC 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
24 LEAD PLASTIC MLPQ
VCCDRV LDRV1 PVCC LDRV2
SW1
24 23 22 21 20 19 HDRV1 BST1 5VCC AGND EN2_B CS+1 1 2 3 4 5 6 7 CS-1 8 CS-2 9 CS+2 10 11 12 IOUT/IMAX VCOMP RT PGND(PAD) 18 17 HDRV2 BST2
SW2
θJA ≈ 30.5o C/W
16 INREFOUT/POK 15 REFIN
14 CSCOMP 13 FB
ELECTRICAL SPECIFICATIONS
Unless otherwise specified, these specifications apply over 5Vcc = 5V, PVcc= 5V, VBST-VSW =5V, EN2_B=GND, and TA = 0 to 70oC. Typical values refer to TA = 25oC. Low duty cycle pulse testing is used which keeps junction and case temperatures equal to the ambient temperature.
PARAMETER Supply Voltage(Vcc) 5VCC ,PVCC Voltage Range 5VCC Supply Current (static) PVCC Supply Current (Dynamic) VBST Voltage Range VBST Supply Current ((Dynamic))
Rev. 2.1 12/01/08
SYM VCC
TEST CONDITION
MIN 4.5 -
TYP 5 6.7 4.4
MAX 5.5
UNITS V mA mA
ICC (Static) REFIN=GND, EN2_B=5V REFIN=5V, EN2_B=GND, ICC Freq=200Khz per phase (Dynamic) CLOAD=2200PF VBST to VSW REFIN=5V, EN2_B=GND, VBST Freq=200Khz per phase (Dynamic) CLOAD=2200PF
4.5
5 4.5
5.5
V mA
2
NX2423
PARAMETER Under Voltage, Vcc & EN2_B VCC-Threshold VCC-Hysteresis EN2_B Threshold EN2_B Hysteresis Reference Voltage Ref Voltage Ref Voltage line regulation Oscillator (Rt) Frequency for each phase Ramp-Amplitude Voltage Ramp Peak Ramp Valley Max Duty Cycle Min Duty Cycle Transconductance Amplifiers(CSCOMP) Open Loop Gain Transconductance Voltage Mode Error Amplifier Gain Open Loop Input Offset Voltage Output Current Source Output Current Sink Output HI Voltage Output LOW Voltage SS (Internal ) Soft Start time POK/INFEROUT Threshold Hysteresis POK Voltage High Side Driver (CL=4700pF) Output Impedance , Sourcing Current Output Impedance , Sinking Current Rise Time Fall Time Deadband Time Low Side Driver (CL=10000pF) Output Impedance, Sourcing Current Output Impedance, Sinking Current
Rev. 2.1 12/01/08
SYM
TEST CONDITION
MIN
TYP
MAX
UNITS
VCC_UVLO VCC_Hyst
VCC Rising VEN2_B Rising
4.1 0.4 0.82 80 0.6 0.2
V V V mV V % KHz V V V % %
VREF
4.5V
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