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US3033
PWM SWITCHER & LINEAR CONTROLLER IC FEATURES
LDO Controller allows the use of a low cost pass transistor for the I/O supply 8 pin SOIC combines switching and linear controller Internal Pre-regulator Eliminates Cross talk between Switching & Linear regulators Automatic shut down of the linear regulator when connected to the Vcc2 Det pin On board MOSFET driver Fastest transient response of any controller method. ( 0 to 100% Duty Cycle in 100 nS ) 1% internal voltage reference Internal Under Voltage Lockout protects MOSFET during start-up
DESCRIPTION
The US3033 IC combines a switching controller and a linear regulator controller all in a compact 8 pin surface mount package, providing a total solution for dual supply processor applications such as an Intel P55C TM, AMD K6TM, as well as Cyrix 6X86LTM and the M2TMprocessors. Typically in these applications a dual supply regulator converts 5V to 3.3V for I/O supply and a jumper programmable supply of 1.25V to 3.5V for CORE supply .The linear regulator controller portion in the US3033 is a programmable controller allowing flexibility for the I/O regulator and has a minimum of 50mA drive current capability designed to provide ample current for an external pass transistor. The IC uses an internal regulator generated from the 12V supply to power the controller as well as the 12V supply to drive the power MOSFET, allowing a low cost N channel MOSFET switch to be used. The IC also includes an error comparator for fast transient response, a precise voltage reference for setting the output voltage as well as a direct drive of the MOSFET for the minimum part count.
APPLICATIONS
Dual supply low voltage processor applications, such as: P55CTM,CYRIX M2TM, POWER PCTM and AMD K6TM Simple 5V to 3.3V switcher for Pentium with AGP or Pentium IITM applications
TYPICAL APPLICATION
5V
C1 R9 Q1 R10 R6 C6 I/O D2 C8 R7 5V R8
12V 8765
V12 Drv2 Vfb2 Gnd
CPU
Vcc2 Det
US3033
Drv1V12swVfb1 Vhyst
1234
C3 L1 Q2 C2 D1 R3 C5
L2 Core R4 C7 R5
3033app1-1.1
Typical application of US3033 in a flexible mother board designed for Intel P55TM,P54TM AMD K5,K6TM as well as Cyrix M1TM and M2TM applications.
Notes: P54C,P55C,Pentium II are trade marks of Intel Corp. K5 & K6 are trade marks of AMD corp. Cyrix 6X86L,M1,M2 are trade marks of Cyrix Corp. Power PC is trade mark of IBM Corp.
PACKAGE ORDER INFORMATION
TA (C) 0 TO 70
Rev. 1.5 1/14/99
8 PIN PLASTIC SOIC (S) US3033CS
4-1
US3033
ABSOLUTE MAXIMUM RATINGS
V12,V12SW Supply Voltages ............................................................. 20V F.B Pin Voltages........................................................ -0.3V to 5V Storage Temperature Range ................................. -65 TO 150C Operating Junction Temperature ............................... 0 TO 150C
PACKAGE INFORMATION
8 PIN PLASTIC SOIC (S)
TOP VIEW
Drv1 1 V12sw
2
8 V12 7 Drv2 6 Vfb2 5 Gnd
Vfb1 3 Vhyst 4
JA =160C/W
ELECTRICAL SPECIFICATIONS
Unless otherwise specified the following specification applies over V12 =V12SW =12V, and TA =0 to 70C. Low duty cycle pulse testing are used which keeps junction and case temperatures equal to the ambient temperature. Linear Controller Section PARAMETER SYM TEST CONDITION MIN TYP MAX UNITS F.B Voltage Initial Accuracy VFB2 TJ =25C, Drv2=VFB2, CL=100uF 1.237 1.250 1.262 V F.B Voltage Total Variation Drv2=VFB2, CL=100uF 1.225 1.250 1.275 V F.B Voltage Line Regulation 104-2
Rev. 1.5 1/14/99
US3033
PIN DESCRIPTIONS
PIN # 3 6 7 5 1 PIN SYMBOL PIN DESCRIPTION A resistor divider from this pin to the output of the switching regulator and ground sets the VFB1 Core supply voltage. The feedback pin of the linear regulator. A resistor divider from this pin to the output of the VFB2 linear regulator and ground sets the I/O supply voltage. The drive pin of the linear regulator. This pin controls the base of a transistor or the gate Drv2 of a MOSFET acting as the series pass element for the linear regulator. This pin is connected to the IC substrate and must be connected to the lowest potential Gnd in the system. The PWM output of the switching controller. This pin is a totem pole drive that is conDrv1 nected to the gate of the power MOSFET. A resistor may be placed from this pin to the gate in order to reduce switching noise. A resistor and a 10pF capacitor is connected from this pin to the VFB1 pin to set the VHYST output ripple voltage for the switching regulator. This pin supplies the voltage to the PWM drive and hysterises circuitry and it is conV12SW nected to the 12V supply. A 1 uF, high frequency capacitor must be connected from this pin to ground to provide the peak current for charging and discharging of the MOSFET. This pin provides the biasing for the chip and drive for the linear regulator controller. It V12 isconnected to 12V supply. A 10 ohm resistor in series from this pin to the 12V supply and a 1uF, high frequency capacitor connected from this pin to Gnd is required to filter the switching noise of the switching regulator.
4 2
8
BLOCK DIAGRAM
V12sw 2
Vhyst 4
Vfb 1 3
V12 8
Drv 2 7
Drv 1 1
UVLO Vref PWM Control
5V Reg
Gnd 5
3033blk1-1.0
1.25V
Vfb2 6
Figure 1 - Simplified block diagram of the US3033
Rev. 1.5 1/14/99
4-3
US3033
TYPICAL APPLICATION
Pentium Dual Supply Application
5V
C1 R11 R10 R9 R13 Q1 C6 I/O
C9 R6
CPU
C8
12V 8765
V12 Drv2 Vfb2 Gnd
D2
R7
5V R8 Vcc2 Det
U1
Drv1V12swVfb1 Vhyst
1234
C3 R3 R1 L1 Q2 C2 C4 R2 D1 JP1 1 2 3 4 5 6 7 8 R5A R5B R5C R5D R5E R4 C5 L2 Core C7
3033app2-1.3
Figure2- Typical application of US3033 in a flexible motherboard with the 4 bit VID output voltage selection. This circuit uses a single jumper that programs the output voltage in 16 steps with 0.1V steps from 2V to 3.5V, designed for Intel P55TM,P54TM, AMD K5 & K6TM as well as Cyrix M1TM and M2TM applications. The Vcc2Det pin automatically shuts down the I/O regulator when a single plane processor is dropped in the socket.
JP1 1-2 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
JP1 3-4 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1
JP1 5-6 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1
JP1 7-8 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
Output Voltage 3.5 3.4 3.3 3.2 3.1 3.0 2.9 2.8 2.7 2.6 2.5 2.4 2.3 2.2 2.1 2.0
0 = Jumper block is installed. 1 = Jumper block is not installed.
4-4
Rev. 1.5 1/14/99
US3033
Pentium Dual Supply Application Parts List
Ref Desig U1 Q1 Q2 D2 D1 L2 L1 R1 R2 R3 R4A * R4B * R5A R5B R5C R5D R5E R6 R7 R8 R9 R10 R11 R13 C1 C2 C3 C4 C5 C6 C7 C8 C9 HS1 HS2 HS3
Description LDO/Switcher IC MOSFET MOSFET Diode, GP Schottky Diode Inductor Inductor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Capacitor Capacitor Capacitor Capacitor Capacitor Capacitor Capacitor Capacitor Capacitor Heat Sink Heat Sink Heat Sink
Qty 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 4 1 1 1 1 1
Part # US3033CS ( 8 pin SOIC) MTP3055 (TO220) IRL3303 (TO220) IRL3103S (TO263) (note 1) 1N4148 MBR1045CT (TO220) MBRB1545CT (TO263) (note1) Core:T50-18,L=4 uH Turns: 10T, 18 AWG L=2 uH 22 ohm,5%, SMT 1206 size 10 ohm, 5%, SMT 1206 size 324 kohm,1%, SMT 0805 size 806 ohm,1%, SMT 0805 size 90.9 kohm,1%, SMT 0805 size 1.24 kohm,1%, SMT 0805 size 2.49 kohm,1%, SMT 0805 size 4.99 kohm,1%, SMT 0805 size 10 kohm,1%, SMT 0805 size 1.30 kohm,1%, SMT 0805 size 2k ohm,1%, SMT 0805 size 1.21k ohm,1%, SMT 0805 size 1 kohm,5%, SMT 0805 size 10 ohm,5%, SMT 0805 size 1k ohm,5%, SMT 0805 size 2.4k ohm,5%, SMT 0805 size 7.5k ohm,5%, SMT 0805 size 6MV1500GX, 1500uF,6.3V, Elect 6MV1500GX, 1500uF,6.3V, Elect 1 uF,Ceramic, SMT 0805 size 470 pF,Ceramic, SMT 0805 size 10 pF,Ceramic, SMT 0805 size 6MV1500GX, 1500uF,6.3V, Elect 6MV1500GX, 1500uF,6.3V, Elect 1 uF,Ceramic, SMT 0805 size 470pF ,Ceramic, SMT 0805 size For MOSFET , 577002 For Schottky Diode , 577002 For Q1 , 507222 (I/O curren<5A) 576602 (I/O current< 3.5A)
Manufacturer Unisem Motorola International Rectifier
Motorola Micro Metal (core)
Sanyo Sanyo Sanyo Sanyo Sanyo
Aavid Aavid Aavid
* R4 is a parallel combination of R4A and R4B. Note 1: For the applications where it is desirable to eliminate the heat sink, the IRL3103S for Q2 and MBR1545CT for D2 in TO263 packages with minimum of 1" square copper pad can be used.
Rev. 1.5 1/14/99
4-5
US3033
TYPICAL APPLICATION
5V to 3.3V for Pentium Application with AGP or Pentium II Application without ATX power supply Dual mode Operation between Switching or Linear mode.
R13 R9 C9
12V
C8
R6
8765
V12 Drv2 Vfb2 Gnd
U1
Drv1V12swVfb1 Vhyst
R7
1234
C3 R10 R1A L1 R1B R3 C5 L2
Figure3- This unique application of US3033 allows the designer to switch between Linear or Switching mode of operation using a single IC. This circuit has the flexibility to be used for low current operation in Linear mode for cost reasons and yet be able to operate in the Switching mode if the load current increases and the heat generated by the Linear operation will be an issue. Table below descibes the components that will be effected for the two modes of operation.
Vout
C7
5V
C1 C2
Q2
C4 R2 D1
R4
R5
3033app3-1.3
Note 1: For the applications where it is desirable to eliminate the heat sink, the IRL3103S for Q2 and MBR1545CT for D2 in TO263 packages with minimum of 1" square copper pad can be used. R3 R4 R5 V VV O VO R6 V V R7 O V
Mode of Operation Switching Linear
L1 V S
L2 V S
D1 C4 VV OO
C5 V O
R1A O V
R1B V O
R2 V O
V = See parts list for value
S = Short
O = Open
Ref Desig U1 Q2 D1 L2 L1 R1A R1B R2 R3 R4 R5 R6 R7 R9 R10 R13 C1,2 C3 C4 C5 C7 C8 C9 HS1
Description LDO/Switcher IC MOSFET Schottky Diode Inductor Inductor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Resistor Capacitor Capacitor Capacitor Capacitor Capacitor Capacitor Capacitor Heat Sink
Qty 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 1 1 1 1 1 1
HS2
Heat Sink
1
Part # US3033CS ( 8 pin SOIC) IRL3303 (TO220) IRL3103S (TO263) (note 1) MBR1045CT (TO220) MBRB1545CT (TO263) (note1) Core:T50-18,L=4 uH Turns: 10T, 18 AWG L=2 uH 2.4k ohm,5%, SMT 1206 size 22 ohm,5%, SMT 1206 size 10 ohm, 5%, SMT 1206 size 249 kohm,1%, SMT 0805 size 1 kohm,1%, SMT 0805 size 576 ohm,1%, SMT 0805 size 180 ohm,1%, SMT 0805 size 100 ohm,1%, SMT 0805 size 10 ohm, 5%, SMT 1206 size 1k ohm, 5%, SMT 1206 size 7.5k ohm, 5%, SMT 1206 size 6MV1500GX, 1500uF,6.3V, Elect 1 uF,Ceramic, SMT 0805 size 470 pF,Ceramic, SMT 0805 size 10 pF,Ceramic, SMT 0805 size 6MV1500GX, 1500uF,6.3V, Elect 1 uF,Ceramic, SMT 0805 size 470pF,Ceramic, SMT 0805 size For MOSFET in Switching mode , 577002 For MOSFET in Linear mode : 507222 (3.3V current<5A), 576602 (3.3V current< 3.5A) For Schottky Diode , 577002
Manufacturer Unisem International Rectifier Motorola Micro Metal (core)
Sanyo Sanyo Sanyo Sanyo
Aavid
Aavid
Rev. 1.5 1/14/99
4-6
US3033
TYPICAL APPLICATION
5V to 3.3V for Pentium Application with AGP or Pentium II Application without ATX power supply Switching mode Operation.
R9
12V
C8
87
65
V12 Drv2 Vfb2 Gnd
U1
Drv1 V12swVfb1 Vhyst
12
C3
34
R3 C5 L2
R1
Vout
L1 C7 Q2 C1 C2 C4 R2 D1 R5
3033app4-1.2
5V
R4
Figure4- The circuit in figure 4 is the application of the US3033 in a switching mode only. This circuit can be used to generate a low cost 5V to 3.3V for either Pentium application with AGP socket or in Pentium II applications where it is desirable to generate an accurate on board 3.3V supply.
Ref Desig U1 Q2 D1 L2 L1 R1 R9 R2 R3 R4 R5 C1,2 C3 C4 C5 C7 C8 HS1 HS2
Description LDO/Switcher IC MOSFET Schottky Diode Inductor Inductor Resistor Resistor Resistor Resistor Resistor Resistor Capacitor Capacitor Capacitor Capacitor Capacitor Capacitor Heat Sink Heat Sink
Qty 1 1 1 1 1 1 1 1 1 1 1 2 1 1 1 1 1 1 1
Part # US3033CS ( 8 pin SOIC) IRL3303 (TO220) IRL3103S (TO263) (note 1) MBR1045CT (TO220) MBRB1545CT (TO263) (note1) Core:T50-18,L=4 uH Turns: 10T, 18 AWG L=2 uH 22 ohm,5%, SMT 1206 size 10 ohm,5%, SMT 0805 size 10 ohm, 5%, SMT 1206 size 249 kohm,1%, SMT 0805 size 1 kohm,1%, SMT 0805 size 576 ohm,1%, SMT 0805 size 6MV1500GX, 1500uF,6.3V, Elect 1 uF,Ceramic, SMT 0805 size 470 pF,Ceramic, SMT 0805 size 10 pF,Ceramic, SMT 0805 size 6MV1500GX, 1500uF,6.3V, Elect 1 uF,Ceramic, SMT 0805 size For MOSFET , 577002 For Schottky Diode , 577002
Manufacturer Unisem International Rectifier Motorola Micro Metal (core)
Sanyo Sanyo Sanyo Sanyo Aavid Aavid
Note 1: For the applications where it is desirable to eliminate the heat sink, the IRL3103S for Q2 and MBR1545CT for D2 in TO263 packages with minimum of 1" square copper pad can be used.
Rev. 1.5 1/14/99
4-7
US3033
APPLICATION INFORMATION
Introduction The US3033 device is an application specific product designed to provide an on board dual supply for the new generation of microprocessors requiring separate Core and I/O supplies. One of the processors fitting this requirement is the new Intel P55CTM multimedia microprocessor. Intel specifies a Core voltage of 2.8V nominal (100mV max) with maximum Core supply current of 6A while the I/O supply is set for 3.3V with a maximum I/O current of 0.65A. However in most applications the I/ O regulator also provides the voltage for other IC functions such as the chip set ,Cache,....etc. Typically a low cost solution such as a Low Dropout Linear Regulator (LDO) is selected to provide the I/O supply with the maximum designed current of 3A , keeping the power dissipation and the heat sink to a reasonable size. The Core supply regulator however if also selected to be a linear regulator , will be dissipating a maximum of 12.6W ((5V-2.8V)X5.7A) of power, which requires a substantial amount of heat sinking and perhaps forced air cooling in order to keep it operational. Some manufacturers suggest using two regulators to current share and therefore distribute the power dissipation equally between the regulators. The problem is that , in order to equally current share you need to sense both currents and force the slave regulator to match the master regulator. This can be done , but at the cost of the circuit complexity and much higher system cost and the total power dissipation is still the same. In fact, if the task is to design a flexible motherboard to accommodate the Cyrix 6X86L or their future MMX processors as well, then the power dissipation could easily reach 20W or more. At this power dissipation level the choice for a switching regulator approach becomes evident. However the main reason that designers have always shied away from the switching regulators is their higher price tag and more complex circuit design that is associated with this kind of technique. The US3033 device is designed to take advantage of the high efficiency of the switching regulator technique for the Core supply while maintaining the low cost LDO regulator for the I/O supply by offering both control functions in a single 8 pin surface mount package. In fact as the typical application circuit shows, one can design a complete flexible motherboard using the US3033 and a few external components yielding a very low component count switching regulator and with an addition of a low cost pass transistor for the I/O supply provide a complete dual supply power soloution. LDO Section The output voltage of the LDO regulator is externally programmable via 2 external resistors from 1.25V to 5V. The internal voltage reference of the The LDO regulator is set to 1.25V and the output of the regulator can be programmed using the following formula: Vout=(1+R1/R2)xVref Where Vref=1.25V Typical R1=Resistor connected from Vout to the Vfb2 pin of US3033 R2=Resistor connected from Vfb2 pin to GND. The US3033 requires the use of an output capacitor as part of the frequency compensation in order to be stable. Typical designs for the microprocessor applications use standard electrolytic capacitors with typical ESR in the range of 50 to 100 m and an output capacitance of 500 to 1000uF. Fortunately as the capacitance increases, the ESR decreases resulting in a fixed RC time constant. The US3033 takes advantage of this phenomena in making the overall regulator loop stable. For most applications a minimum of 100uF aluminum electrolytic capacitor such as Sanyo, MVGX series ,Panasonic FA series or Nichicon PL series insures both stability and good transient response. An external filtering is suggested as shown in the application circuit that reduces the switching ripple that might show in the output of the LDO regulator. Switching Controller Operation The operation of the switching controller is as follows : after the power is applied, the output drive, "Drv1" goes to 100% duty cycle and the the current in the inductor charges the output capacitor causing the output voltage to increase. When output reaches a pre-programmed set point the feedback pin "Fb1" exceeds 1.25V causing the output drive to switch low and the "Vhyst" pin to switch high which jumps the feedback pin higher than 1.25V resulting in a fixed output ripple which is given by the following equation : Vo=(Rt/Rh)x11 Where: Rt=Top resistor of the output divider, resistor connected from Vout to the Vfb1 pin of US3033 Rh=Bottom resistor of the divider, resistor connected from Vfb1 pin to Vhyst pin. For example, if Rt=1k and Rh=422k, then the output ripple is : Vo=(1/422)x11=26mV
4-8
Rev. 1.5 1/14/99
US3033
The advantage of fixed output ripple is that when the output voltage changes from 2V to 3.5V, the ripple voltage remains the same which is important in meeting the Intel maximum tolerance specification. Switcher Output Voltage Setting The output voltage of the switcher can be set using the following equations. Assuming , Vo=3.38V and the selected output ripple is 1.3%(44mV) of the output voltage, a set of equations are derived that selects the resistor divider and the hysterises resistor. Assuming, Rt=1k , 1% Rh=(11*Rt)/Vo Where: Rt=Top resistor of the resistor divider Rh=Hysterises resistor connected between pins 3 and 4 of the US3033 Vo=Selected output ripple (typically 1% to 2% of output voltage) Assuming, Vo=44mV Rh=(11*1000)/0.044=250 k Select Rh=249 k , 1% The bottom resistor of the divider is then calculated using the following equations: Rb=Rt/X Where: Rb=Bottom resistor of the divider X=[(Vo + (Vo/2))/Vref] - 1 Vref=1.25 V typ. X=[(3.38+ (0.044/2))/1.25] - 1 = 1.72 Rb=1000/1.72=580 Select Rb=576 , 1% Frequency Calculation The US3033 frequency of operation is calculated using the following formula: Fs=[(Vo*(1-D)*ESR)]/(L*Vo) (MHz) Where: Vo=Output voltage (V) D=Duty cycle ESR=Output capacitor ESR (V) L=Output inductance (uH) Vo=Output ripple voltage (V) For our example: D(Vo + Vf)/Vin Where, Vf=Forward voltage drop of the Schotky diode D=(3.38 + 0.5)/5=0.78 The ESR=18m for 2 of the Sanyo 1500uF, 6MV1500GX caps. If L=3.5uH then, Fs is calculated as follows: Fs=[(3.38*(1-0.78)*0.018)]/(3.5*0.044)= 0.087 Mhz = 87 kHz
Rev. 1.5 1/14/99
4-9

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