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AIC1579/L
Step-Down Switching Regulator Controller
FEATURES
Operation Voltage up to 15V. Simple Voltage-Mode PWM Control. Fast Transient Response. 2V and 1.3V 2% Feedback Voltage Reference Option. Adjustable Current Limit without External Sense Resistors. 200KHz Free-Running Oscillator. Short-Circuit Protection with Low Short Circuit Output Current.
DESCRIPTION
The AIC1579 is a high-power, high-efficiency voltage-mode switching regulator controller for motherboard VI/O power supply applications. Designed to drive an N-channel MOSFET in a standard buck topology, the AIC1579 features a high voltage CMOS output driver, short-circuit protection, and 8-pin package. An external 4-bit Digital-to-Analog Converter (DAC) can be used along with the AIC1579 to adjust the output voltage from 2.0V to 3.5V in 0.1V increments. Table 1 on the following page specifies the corresponding output voltage for 16 combinations of DAC inputs as in the typical application circuit. The 200KHz switching frequency allows for using small external components while maintaining high conversion efficiency. The 11MHz bandwidth and 6V/S slew rate of the error amplifier ensures high converter bandwidth and fast transient response. The AIC1579 provides adjustable overcurrent and short-circuit protections by sensing the output current across the on resistance of the external N-channel MOSFET rather than an external low value sense resistor. The AIC1579L provides lower reference voltage (1.30V) than the default (2.00V, AIC1579) for lower VOUT requirement.
APPLICATIONS
Power Supply for Motherboard VGTL (1.5V Output) Power Supply for Motherboard VI/O. High-Power 5V to 3.xV DC/DC Regulators. Low-Voltage Distributed Power Supplies.
Analog Integrations Corporation DS-1579-01 Nov 9, 00
4F, 9, Industry E. 9th Rd, Science Based Industrial Park, Hsinchu Taiwan, ROC TEL: 886-3-5772500 FAX: 886-3-5772510
www.analog.com.tw
1
AIC1579/L
ORDERING INFORMATION
AIC1579 XXX
PACKAGE TYPE N: PLASTIC DIP S: SMALL OUTLINE TEMPERATURE RANGE C=0C~+70C REFERENCE VOLTAGE DEFAULT: 2.00V L: 1.30V
ORDER NUMBER
AIC1579CN AIC1579LCN (PLASTIC DIP) AIC1579CS AIC1579LCS (PLASTIC SO)
PIN CONFIGURATION
TOP VIEW OCSET 1 SS 2 COMP 3 FB* 4 *AIC1579: 2.00V AIC1579L: 1.30V 8 VCC 7 UGATE 6 PHASE 5 GND
TYPICAL APPLICATION CIRCUIT
C2 1000pF R1 C5 0.1F 2.2K 1%
OCSET SS VCC UGATE
*C1 MUST BE VERY CLOSE TO VCC PIN 10 R8 C1* 1F M1 RFP45N03L + C3 1000Fx2 3.3V/10A VOUT L2 7H + C4 1000 F x 6
12V L1 1H 5V
C6 33P C7
COMP PHASE FB GND
AIC1579
R2
90.9K 1% 1000pF R4 VID0 VID1 VID2 VID3 60.4K 1% R5 30.1K 1% R6 15.0K 1% R7 7.5K 1% R3 3.01K 1%
D1 BYV118
Switching Regulator for Pentium VCORE Supply
2
AIC1579/L
Table 1. Output Voltage Program VID3 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 VID2 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 VID1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 VID0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 VOUT 2.00V 2.10V 2.20V 2.30V 2.40V 2.50V 2.60V 2.70V 2.80V 2.90V 3.00V 3.10V 3.20V 3.30V 3.40V 3.50V
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC .................................................................................................... 15V Input, Output, or I/O Voltage .................................................... GND - 0.3V to VCC+0.3V ESD Classification ................................................................................................. Class 2 Recommended Operating Conditions Supply Voltage, VCC ........................................................................................... 12V 10% Ambient Temperature Range ............................................................................ 0C~70C Junction Temperature Range ......................................................................... 0C~ 100C Thermal Information Thermal Resistance, JA (Typical, Note 1) SOIC Package ....................................................................................... 100C/W SOIC Package (with 3 in2 of Copper) ..................................................... 90C/W Maximum Junction Temperature (Plastic Package) .............................................. 150C Maximum Storage Temperature Range ................................................... -65C~150C Maximum Lead Temperature (Soldering 10 Sec) ................................................ 300C Note 1: JA is measured with the component mounted on an evaluation PC board in free air.
TEST CIRCUIT
Refer to TYPICAL APPLICATION CIRCUIT.
3
AIC1579/L
ELECTRICAL CHARACTERISTICS
specified.)
PARAMETER VCC Supply Current Nominal Supply Power-On Reset VCC Threshold Oscillator Frequency Max. Duty Cycle Internal Reference Voltage Reference Voltage Error Amplifier DC Gain Gain-Bandwidth Product Slew Rate Gate Driver Upper Gate Source Upper Gate Sink Protection OCSET Current Source SS Current VOCSET =4.5VDC IOCSET ISS 170 200 10 230 A A RUGATE RUGATE 8 5.5 12 10 GBW SR 76 11 6 dB MHz V/S AIC1579 AIC1579L 1.96 1.27 2.00 1.30 2.04 1.33 V 160 200 240 100 KHz % VOCSET=4.5V 10.4 V UGATE Open IVCC 2.3 mA TEST CONDITIONS
(VCC= 12V, Ta=25C, unless otherwise
SYMBOL MIN. TYP. MAX. UNIT
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs. Load Current
100 90
OCSET Current vs. Temperature
200
Vo=3.5V Vo=2.0V Vo=1.3V
Efficiency (%)
80 70 60 50 40
Clset (A)
198
196
Tc=134ppm/ C@ 0~100C
194
192
30 1 2 3 4
IOUT (A)
5
6
7
8
9
10
11
-40
-20
0
20
Temperature (C)
40
60
80
100
120
140
160
4
AIC1579/L
TYPICAL PERFORMANCE CHARACTERISTICS(Continued)
SS Current vs. Temperature
9.9
Over-Current Operation
9.8
Soft Start (A)
9.7
9.6
Tc = 306 ppm/C @ 0~100C
9.5
9.4
9.3-40
-20
0
20
40
60
80
100
120
140
160
Temperature (C)
Soft Start Initiates Output
Transient Response
5
AIC1579/L
BLOCK DIAGRAM
SS PHASE OCSET
+ 10A Over Current 200A Soft Start 4V PWM Comparator REF. + Error AMP Oscilator Gate Control Power-ON Reset
VCC
UGATE
FB COMP
GND
PIN DESCRIPTIONS
PIN 1: OCSET - Current limit sense pin. Connect a resistor ROCSET from this pin to the drain of the external MOSFET. ROCSET, an internal 200A current source (IOCSET), and the external MOSFET onresistance (RDS(ON)) jointly set the overcurrent trip point according to the following equation:
comparator. A RC network is connected to FB pin to compensate the voltage-control feedback loop of the converter. PIN 4: FB - The error amplifier inverting input pin. The FB pin and COMP pin are used to compensate the voltage-control feedback loop. Ground pin. Overcurrent detection pin. Connect the PHASE pin to source of the external NMOSFET. This pin detects the voltage drop across the MOSFET RDS(ON) for overcurrent protection.
PIN 5: GNDPIN 6: PHASE-
IPEAK
IOCSET x ROCSET = RDS(ON)
If FB pin voltage is sensed to be below 50% of the internal voltage reference VDAC, the overcurrent comparator cycles the soft-start function. PIN 2: SS - Soft start pin. Connect a capacitor from this pin to ground. An internal 10A current source provides soft start function for the converter.
PIN 7: UGATE- External MOSFET gate drive pin. Connect this pin to gate of the external MOSFET. PIN 8: VCC -The chip power supply pin. Recommended supply voltage is 12V.
PIN 3: COMP - External compensation pin. This pin is connected to error amplifier output and PWM
6
AIC1579/L
APPLICATION CIRCUIT
C2 1000pF R1 C5 0.01F 2.2K 1%
OCSET SS COMP FB VCC UGATE PHASE GND
*C1 MUST BE VERY CLOSE TO VCC PIN 10 R8 C1* 1F M1 RFP45N03L + C3 1000FX2 L2 D1 R3 BYV118 7H + C4 1000F x 6 1.5V/10A VOUT
12V L1 1H 5V
C6 33P R2 90.9K 1%
AIC1579L C7
1000pF 1% 13K R4
1% 2K *VOUT=1.3V x (1+ R3/R4)
PHYSICAL DIMENSIONS
8 LEAD PLASTIC SO (unit: mm)
D
SYMBOL A
H E
MIN 1.35 0.10 0.33 0.19 4.80 3.80 5.80 0.40
MAX 1.75 0.25 0.51 0.25 5.00 4.00 6.20 1.27
A1 B C D E
e A C
A1
e H L
L
1.27(TYP)
B
7
AIC1579/L
8 LEAD PLASTIC DIP (unit: mm)
D
SYMBOL A1
E1
MIN 0.381 2.92 0.35 0.20 9.01 7.62 6.09 -- 2.92
MAX -- 4.96 0.56 0.36 10.16 8.26 7.12 10.92 3.81
A2 b C
E
D E
C
A2 A1
L
E1 e eB L
2.54 (TYP)
eB b e
8

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