Datasheet US3033CS Datasheet (UNISEM)

Page 1

US3033

PWM SWITCHER & LINEAR

CONTROLLER IC

FEATURESFEATURES

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

APPLICATIONSAPPLICATIONS

Dual supply low voltage processor applications, such as: P55C,CYRIX M2, POWER PC and AMD K6 Simple 5V to 3.3V switcher for Pentium with AGP or Pentium II applications

DESCRIPTIONDESCRIPTION

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 , AMD K6, as well as Cyrix 6X86L and the M2processors. 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.

TYPICAL APPLICATIONTYPICAL APPLICATION

Drv1V12swVfb1Vhyst

1 2 3 4

US3033

R10

5678

GndVfb2Drv2V12

D1C2

R3 C5

12V

Typical application of US3033 in a flexible mother board designed for Intel P55,P54

AMD K5,K6 as well as Cyrix M1 and M2 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.

I / O

CPU

Vcc2 Det

Core

3033app1-1.1

PACKAGE ORDER INFORMATIONPACKAGE ORDER INFORMATION

TA (°C) 8 PIN PLASTIC SOIC (S) 0 TO 70 US3033CS

Rev. 1.5 1/14/99

4-1

Page 2

US3033

ABSOLUTE MAXIMUM RATINGSABSOLUTE MAXIMUM RATINGS

V12,V12SW Supply Voltages ............................................................. 20V

F.B Pin Voltages........................................................ -0.3V to 5V

Storage Temperature Range ................................. -65 TO 150°C

Operating Junction Temperature ............................... 0 TO 150°C

PACKAGE INFORMATIONPACKAGE INFORMATION

8 PIN PLASTIC SOIC (S)

TOP VIEW

Drv1

V12sw

Vfb1

Vhyst Gnd

θJA =160°C/W

V12

Drv2

Vfb2

ELECTRICAL SPECIFICATIONSELECTRICAL SPECIFICATIONS

Unless otherwise specified the following specification applies over V12 =V12SW =12V, and TA =0 to 70°C. 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 =25°C, 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 10<V12<14V,Drv2=VFB2, CL=100uF 0.2 % F.B Input Bias Current IFB2 VFB2 =1.25V -1 +1 uA Maximum Drive Current IDRVMAX VFB2 =1V, VFB1 =1.5V 50 mA V12 Supply Current I12 VFB2 =1V, VFB1 =1.5V, IDRV2 =0 5 mA

Switching Controller Section PARAMETER SYM TEST CONDITION MIN TYP MAX UNITS

F.B Voltage Initial Accuracy VFB1 TJ =25°C 1.237 1.250 1.262 V F.B Voltage Total Variation 1.225 1.250 1.275 V F.B Voltage Line Regulation 0.2 % F.B Input Bias Current IFB1 VFB1 =1.25V -1 +1 uA Min On Time VFB1 is sq wave with 300 ns on 800 nS

time and 2 uS off time

Min Off Time VFB1 is sq wave with 300 ns off 800 nS

time and 2 uS on time Vhyst pin output-HI ISOURCE =500uA, VFB1 =1.5V 11 V Vhyst pin output-LO ISINK =500uA, VFB1 =1V 1 V Supply Current I12SW VFB1 =1V , VFB2 =1.5V 10 mA Maximum Duty Cycle DMAX VFB1 =1V 100 % Minimum Duty Cycle DMIN VFB1 =1.5V 0 % Gate Drive Rise/Fall Time VGATE Load=IRL3303 70 nS

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PIN DESCRIPTIONSPIN DESCRIPTIONS

PIN # PIN SYMBOL PIN DESCRIPTION

3 VFB1 6 VFB2 7 Drv2 5 Gnd 1 Drv1

4 VHYST 2 V12SW

8 V12

A resistor divider from this pin to the output of the switching regulator and ground sets the Core supply voltage. The feedback pin of the linear regulator. A resistor divider from this pin to the output of the 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 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 in the system. The PWM output of the switching controller. This pin is a totem pole drive that is connected 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 output ripple voltage for the switching regulator. This pin supplies the voltage to the PWM drive and hysterises circuitry and it is connected 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 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.

US3033

BLOCK DIAGRAMBLOCK DIAGRAM

V12sw Vhyst

2 4 3

Drv 1

Gnd

Vfb 1

UVLO

Vref

PWM Control

3033blk1-1.0

Figure 1 - Simplified block diagram of the US3033

1.25V

5V Reg

V12

Drv 2

Vfb2

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US3033

TYPICAL APPLICATIONTYPICAL APPLICATION

Pentium Dual Supply Application

12V

R10

Drv1V12swVfb1 Vhyst

1 2 3 4

D1R2

R11

GndVfb2Drv2V12

5678

JP1

R13

R3 C5

R5A R5B R5C R5D R5E

I / O

CPU

Vcc2 Det

Core

7 8

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 P55,P54, AMD K5 & K6 as well as Cyrix M1 and M2 applications. The Vcc2Det pin automatically shuts down the I/O regulator when a single plane processor is dropped in the socket.

JP1 JP1 JP1 JP1 Output 1-2 3-4 5-6 7-8 Voltage 0 0 0 0 3.5 0 0 0 1 3.4 0 0 1 0 3.3 0 0 1 1 3.2 0 1 0 0 3.1 0 1 0 1 3.0

0 = Jumper block is installed. 1 = Jumper block is not installed.

0 1 1 0 2.9 0 1 1 1 2.8 1 0 0 0 2.7 1 0 0 1 2.6 1 0 1 0 2.5 1 0 1 1 2.4 1 1 0 0 2.3 1 1 0 1 2.2 1 1 1 0 2.1 1 1 1 1 2.0

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Pentium Dual Supply Application Parts List

Ref Desig Description Qty Part # Manufacturer

U1 LDO/Switcher IC 1 US3033CS ( 8 pin SOIC) Unisem Q1 MOSFET 1 MTP3055 (TO220) Motorola Q2 MOSFET 1 IRL3303 (TO220) International

IRL3103S (TO263) (note 1) Rectifier D2 Diode, GP 1 1N4148 D1 Schottky Diode 1 MBR1045CT (TO220)

MBRB1545CT (TO263) (note1) Motorola L2 Inductor 1 Core:T50-18,L=4 uH Micro Metal

Turns: 10T, 18 AWG (core) L1 Inductor 1 L=2 uH R1 Resistor 1 22 ohm,5%, SMT 1206 size R2 Resistor 1 10 ohm, 5%, SMT 1206 size R3 Resistor 1 324 kohm,1%, SMT 0805 size R4A * Resistor 1 806 ohm,1%, SMT 0805 size R4B * Resistor 1 90.9 kohm,1%, SMT 0805 size R5A Resistor 1 1.24 kohm,1%, SMT 0805 size R5B Resistor 1 2.49 kohm,1%, SMT 0805 size R5C Resistor 1 4.99 kohm,1%, SMT 0805 size R5D Resistor 1 10 kohm,1%, SMT 0805 size R5E Resistor 1 1.30 kohm,1%, SMT 0805 size R6 Resistor 1 2k ohm,1%, SMT 0805 size R7 Resistor 1 1.21k ohm,1%, SMT 0805 size R8 Resistor 1 1 kohm,5%, SMT 0805 size R9 Resistor 1 10 ohm,5%, SMT 0805 size R10 Resistor 1 1k ohm,5%, SMT 0805 size R11 Resistor 1 2.4k ohm,5%, SMT 0805 size R13 Resistor 1 7.5k ohm,5%, SMT 0805 size C1 Capacitor 1 6MV1500GX, 1500uF,6.3V, Elect C2 Capacitor 1 6MV1500GX, 1500uF,6.3V, Elect Sanyo C3 Capacitor 1 1 uF,Ceramic, SMT 0805 size C4 Capacitor 1 470 pF,Ceramic, SMT 0805 size Sanyo C5 Capacitor 1 10 pF,Ceramic, SMT 0805 size Sanyo C6 Capacitor 1 6MV1500GX, 1500uF,6.3V, Elect Sanyo C7 Capacitor 4 6MV1500GX, 1500uF,6.3V, Elect Sanyo C8 Capacitor 1 1 uF,Ceramic, SMT 0805 size C9 Capacitor 1 470pF ,Ceramic, SMT 0805 size HS1 Heat Sink 1 For MOSFET , 577002 Aavid HS2 Heat Sink 1 For Schottky Diode , 577002 Aavid HS3 Heat Sink 1 For Q1 , 507222 (I/O curren<5A) Aavid

576602 (I/O current< 3.5A)

US3033

* 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.

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US3033

TYPICAL APPLICATIONTYPICAL 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.

R10

R1A R1B

12V

Mode of Operation L1 L2 D1 C4 C5 R1A R1B R2 R3 R4 R5 R6 R7 Switching V V V V V O V V V V V V O Linear S S O O O V O O O V O V V

R13

GndVfb2Drv2V12

Drv1V12swVfb1Vhyst

1 2 3 4

5678

R3 C5

Figure3- This unique application of US3033 allows the de-

signer to switch between Linear or Switching mode of

D1R2

3033app3-1.3

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

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.

V = See parts list for value S = Short O = Open

Ref Desig Description Qty Part # Manufacturer

U1 LDO/Switcher IC 1 US3033CS ( 8 pin SOIC) Unisem Q2 MOSFET 1 IRL3303 (TO220) International

IRL3103S (TO263) (note 1) Rectifier

D1 Schottky Diode 1 MBR1045CT (TO220)

MBRB1545CT (TO263) (note1) Motorola

L2 Inductor 1 Core:T50-18,L=4 uH Micro Metal

Turns: 10T, 18 AWG (core) L1 Inductor 1 L=2 uH R1A Resistor 1 2.4k ohm,5%, SMT 1206 size R1B Resistor 1 22 ohm,5%, SMT 1206 size R2 Resistor 1 10 ohm, 5%, SMT 1206 size R3 Resistor 1 249 kohm,1%, SMT 0805 size R4 Resistor 1 1 kohm,1%, SMT 0805 size R5 Resistor 1 576 ohm,1%, SMT 0805 size R6 Resistor 1 180 ohm,1%, SMT 0805 size R7 Resistor 1 100 ohm,1%, SMT 0805 size R9 Resistor 1 10 ohm, 5%, SMT 1206 size R10 Resistor 1 1k ohm, 5%, SMT 1206 size R13 Resistor 1 7.5k ohm, 5%, SMT 1206 size C1,2 Capacitor 2 6MV1500GX, 1500uF,6.3V, Elect Sanyo C3 Capacitor 1 1 uF,Ceramic, SMT 0805 size C4 Capacitor 1 470 pF,Ceramic, SMT 0805 size Sanyo C5 Capacitor 1 10 pF,Ceramic, SMT 0805 size Sanyo C7 Capacitor 1 6MV1500GX, 1500uF,6.3V, Elect Sanyo C8 Capacitor 1 1 uF,Ceramic, SMT 0805 size C9 Capacitor 1 470pF,Ceramic, SMT 0805 size HS1 Heat Sink 1 For MOSFET in Switching mode , 577002 Aavid

For MOSFET in Linear mode :

507222 (3.3V current<5A),

576602 (3.3V current< 3.5A) HS2 Heat Sink 1 For Schottky Diode , 577002 Aavid

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1/14/99

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US3033

TYPICAL APPLICATIONTYPICAL APPLICATION

5V to 3.3V for Pentium Application with AGP or Pentium II Application without ATX power supply Switching mode Operation.

12V

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.

Drv1V12swVfb1Vhyst

1 2 3 4

Figure4- The circuit in figure 4 is the application of the US3033 in a switching mode only. This circuit can be used to

5678

GndVfb2Drv2V12

R3 C5

Vout

D1R2

3033app4-1.2

Ref Desig Description Qty Part # Manufacturer

U1 LDO/Switcher IC 1 US3033CS ( 8 pin SOIC) Unisem Q2 MOSFET 1 IRL3303 (TO220) International

IRL3103S (TO263) (note 1) Rectifier

D1 Schottky Diode 1 MBR1045CT (TO220)

MBRB1545CT (TO263) (note1) Motorola

L2 Inductor 1 Core:T50-18,L=4 uH Micro Metal

Turns: 10T, 18 AWG (core) L1 Inductor 1 L=2 uH R1 Resistor 1 22 ohm,5%, SMT 1206 size R9 Resistor 1 10 ohm,5%, SMT 0805 size R2 Resistor 1 10 ohm, 5%, SMT 1206 size R3 Resistor 1 249 kohm,1%, SMT 0805 size R4 Resistor 1 1 kohm,1%, SMT 0805 size R5 Resistor 1 576 ohm,1%, SMT 0805 size C1,2 Capacitor 2 6MV1500GX, 1500uF,6.3V, Elect Sanyo C3 Capacitor 1 1 uF,Ceramic, SMT 0805 size C4 Capacitor 1 470 pF,Ceramic, SMT 0805 size Sanyo C5 Capacitor 1 10 pF,Ceramic, SMT 0805 size Sanyo C7 Capacitor 1 6MV1500GX, 1500uF,6.3V, Elect Sanyo C8 Capacitor 1 1 uF,Ceramic, SMT 0805 size HS1 Heat Sink 1 For MOSFET , 577002 Aavid HS2 Heat Sink 1 For Schottky Diode , 577002 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.

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4-7

Page 8

US3033

APPLICATION INFORMATIONAPPLICATION 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 P55C 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 func-

tions 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 transis-

tor 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 mΩ 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

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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=1kΩ , 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 kΩ Select Rh=249 kΩ , 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 Ω Select Rb=576 Ω , 1%

US3033

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=18mΩ 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

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4-9