3 Shunt Resistor

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www.fairchildsemi.com

2010 Fairchild Semiconductor Corporation 1 RD344_FNA41560 Rev. 0.0.1

Reference Design RD-344

Fairchild Motion-SPMFNA41560 Three-Shunt Design

The following reference design supports a design of FNA41560. It should be used in conjunction with

the FNA41560 datasheet as well as Fairchilds application notes (AN-9070, AN-9071, AN-9072) andtechnical support team. Please visit Fairchilds website at http://www.fairchildsemi.com.

Application Fairchild DeviceInput Voltage

RangeTypical Power

RatingTopology

Home Appliance

(Air-Conditioner)

FNA41560

MMSZ5252B

LMV324

300~400VDC 1500WThree Shunt Solution

(Single Ground)

Key Features

FNA41560

600V-15A 3-phase IGBT inverter bridge including control ICs for gate driving and protection

Easy PCB layout due to built-in bootstrap diode and independent VS pin

Divided negative DC-link terminals for inverter current-sensing applications

Single-grounded power supply due to built-in HVIC

Built-in NTC thermistor for over-temperature monitoring

Isolation rating of 2000Vrms/min.

MMSZ5252B Silicon planar power Zener diodes, DO-41 glass case

24V/1.0W rating Zener diode

For use in stabilizing and clipping circuits with high power rating

Standard Zener voltage tolerance: 5%

LMV324

General-purpose, low-voltage, rail-to-rail output amplifier

80A supply current per channel

1.2MHz GBP(Gain Bandwidth Product)

1.5V/s slew rate

Low offset voltage


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1.Schematics

Figure 1. Block Diagram of Air Conditioner


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R31 100

R21 100

C510uF/35V

C6104

C710uF/35V

C810uF/35V

C26220uF/35V

C24

102

R17 100

R20 100

C140.1uF 630V

R280.008 2W

5V line

R31

4.7K

C25

102

C17

102

C16

102C15

102

R16 100

R18 100

R19 100

5V line

15V line

(1) UH

P

N

W

V

U15V line

C32104

C31100uF/16V

C28333

R35 62

COM

VCC

IN(UL)

IN(VL)

IN(WL)

VFO

CSC

OUT(WL)

OUT(VL)

OUT(UL)

NW (9)

NV (8)

NU (7)

W (6)

V (5)

U (4)

P (3)

(23) VS(V)

(26) VB(U)

(19) IN(VH)

(22) VB(W)

(10) CSC

(11) VFO

(14) IN(UL)

(13) IN(VL)

(12) IN(WL)

(15) COM

UVS

UVB

OUT(UH)

UVS

WVS

OUT(WH)

COM

VCC

OUT(VH)

IN(UH) VVS

IN(VH)

(25) VS(U)

(24) VB(V)

(21) VS(W)

(20) IN(UH)

(18) V(WH)

(17) VCC(H)

VTH (1)

RTH (2)

VVS

VVB

WVS

WVB

IN(WH)

(16) VCC(L)

ZD1

MMSZ5252B

C20

102

C19

102

C18

102

R9 6.8K 1%

5V line

Motion-SPM FNA41560

J1

(2)VH(3) WH

(4) UL(5) VL(6) WL(7) FO

(8) VNTC

(9) VDD

(10) VCC

(11) GND

NTC

ZD2MMSZ5252B

C10104

ZD3MMSZ5252B

C9104

ZD4MMSZ5252B

C27104

R

4

5V line

1

7

8

14

11

3

2

5

6

10

9

12

13

U1LMV324

R320.008 2W

R330.008 2W

R340.0082W

J2

(1) VIU

(2) VIV

(3) VIW

5V

R6 39K 1%

C4 101

R14 39K 1%

C13101

R27 39K 1%

C23 101

R407.87K 1%

C30 510

R1, R7, R8,

R15, R22, R29

: 78.7K 1%

C3, C12, C22

: 101

R1

R7

C3

R8

R15

C12

R29

C22

R22

R3 1.8K 1%

R51.8K 1%

R2 1.0K 1%

R4 1.0K 1%

R111.8K 1%

R131.8K 1%

R101.0K 1%

R121.0K 1%

C2 101

C11 101

R241.8K 1%

R261.8K 1%

R231.0K 1%

R251.0K 1%

C21 101

R371.8K 1%

R39 1.8K 1%

R361.0K 1%

R381.0K 1%

C29101

C33 101

R41 8.2K 1%

Figure 2. Reference Design for 3-Phase Inverter


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2.Key Parameter Design

2.1. Selection of Bootstrap Capacitance (CBS)

The bootstrap capacitor can be calculated by:

BS

LeakBS

V

tIC

=

(1)

where:

t = maximum on pulse width of high-side IGBT;

VBS = the allowable discharge voltage of the CBS (voltage ripple); and

ILeak= maximum discharge current of the CBS.

Normally, ILeakconsist of the following items:

- Gate charge for turning the high-side IGBT on

- Quiescent current to the high-side circuit in the HVIC- Level-shift charge required by level-shifters in HVIC

- Leakage current in the bootstrap diode

- CBScapacitor leakage current (ignored for non-electrolytic capacitors)

- Bootstrap diode reverse recovery charge.

Practically, 2mA of ILeakis recommended for Mini DIP SPM family in Motion-SPM

products (IPBS(operating VBSsupply current) value in datasheet) .

Calculation Examples of CBS

ILeak= circuit current (IPBS) = 2mA (recommended value)VBS = discharged voltage = 0.1V (recommended value)

t = maximum on pulsewidth of high-side IGBT = 2ms (depends on system)

6

min_ 100.41.0

2.02 =

=

=

V

msmA

V

tIC

BS

LeakBS

(2)

More than 2~3times 8FStandard nominal capacitance 10F.


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2.2. Design of Current-Sensing Circuit

Figure 3. General Circuit for Current Sensing

Figure 4. Typical Low-Side Current-Sensing Circuit

FNA41560 has a divided negative DC-link terminal (NU, NV, NW) for current sensing to

simplify current-sensing circuit design. Figure 3and Figure 4 show the typical three-shunt

current-sense circuit using the FNA41560 in Motion-SPM.

The value of application circuit is calculated by the following equations.

In Figure 5, the output voltage of op-amp (VOUT) can be calculated by:

)()(65

5

42

7min,min,

RR

RV

RR

RVV refShuntout

++

+=

(3)

)()(65

5

42

7max,max,

RR

R

VRR

R

VV refShuntout +++= (4)

According to Equation 3, the voltage between shunt resistor (VShunt) can be calculated by:

7

42

65

5maxmax, ]

)([

R

RR

RR

RVVV refoutShunt

+

+=

(5)

7

42

65

5minmin, ]

)([

R

RR

RR

RVVV refoutShunt

+

+=

(6)


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2.3. Calculation Examples for Current-Sensing Circuitry

Calculation Conditions

DUT: FNA41560

Op-Amp: LMV324

Resistance of shunt resistor: 8m, 1% tolerance, KOA

SC trip current: 22.5A (1.5 x IC (rated current))

Input voltage range of ADC of MCU: 0~+5V

Components value: refer to Figure 5 and Figure 6

Figure 5. Application Circuit of Current Sensing (VCC=5.0V, Voltage Gain=13.9)

Figure 6. Application Circuit of Current Sensing (VCC=3.3V, Voltage Gain=9.1)

VCC, Vref=5.0[V]Voltage gain=13.9Bandwidth = 86[kHz]

VCC, Vref=3.3VVoltage gain=9.2Bandwidth = 130[kHz]


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Figure 7. VADC (Input Voltage of AD Converter of MCU) vs. VShunt (Voltage of Shunt Resistor) in CurrentFeedback Circuitry (Figure 5, Figure 6)

According to calculation conditions, Figure 5, and Equations 5 and 6, the voltage

between shunt resistor (VShunt,min, VShunt,max) can be calculated by:

Vk

k

kk

kVV

R

RR

RR

RVVV refoutShunt 179.0

39

8.2]

7.787.78

7.7850[]

)([

7

42

65

5minmin, =

+

=

+

+=

Vk

k

kk

kVV

R

RR

RR

RVVV refoutShunt 179.0

39

8.2]

7.787.78

7.7855[]

)([

7

42

65

5maxmax, =

+

=

+

+=

According to Equation 3 and 4, the voltage of op-amp output can be calculated by:

Vkk

kVk

kVRR

RVRR

RVV refShuntout 0)7.787.78

7.785()8.2

39179.0()()(65

5

42

7min,min, =

+

+

=

++

+=

Vkk

kV

k

kV

RR

RV

RR

RVV refShuntout 0.5)

7.787.78

7.785()

8.2

39179.0()()(

65

5

42

7max,max, =

+

+

=

++

+=

For low control voltage systems, such as VCC=3.3V, the same consideration can be

performed on the circuit shown in Figure 6. The circuit in Figure 6 has a same

performance as the circuit in Figure 5. Figure 7 shows VShuntvs. VADCaccording to VCC

variation (3.3V, 5.0V) and gain of op-amp.

2.4. Components Calculation Examples for SCP

Calculation Conditions DUT: FNA41560

Op-Amp: LMV324

Resistance of shunt resistor: 8m, 1% tolerance, KOA

SC trip current: 22.5A (1.5 x IC (rated current), can be changed by designer)

SC trip reference voltage: VSC(min)=0.45V, VSC(typ)=0.50V, VSC(max)=0.55V

Components value: refer to Figure 8


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Vkk

kVV

RR

RV shuntshuntout 505.0179.0)

8.10.1

87.7()()(

98

13=

+

=

+=

+

Figure 8. Application Circuit of SCP(Short-Circuit Current Protection)

2.5. Power Rating of Shunt Resistor Calculation Example

Calculation Conditions

Vendor of shunt resistor: KOA (TLR3AW 8m)

Maximum load current of inverter (Irms): 10Arms

Shunt resistor value at TC=25oC (RSHUNT): 8.0m

Derating ratio of shunt resistor at TSHUNT=100oC: 65%

Safety margin: 20%

Figure 9. Derating Curve of Shunt Resistor (KOA, TLA Series)

PSHUNT (I2rmsx RSHUNTx Margin) / Derating ratio)=(10

2x 0.008x 1.2) / 0.65=1.48W

(Therefore, the proper power rating of shunt resistor is over 2.0W)


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2.6. Temperature-Monitoring Circuit

-20 -10 0 10 20 30 40 50 60 70 80 90 100 110 1200

50

100

150

200

250

300

350

400

450

500

550

600

MINTYPMAX

R-T Curve

Resistance[k]

Temperature TTH

[]

Figure 10. R-T Curve of NTC thermistor in Mini DIP SPM Package

Figure 10 is R-T curve of the integrated NTC thermistor in Mini DIP SPM package.

For R-T table of NTC thermistor, refer to application note Mini DIP SPM(AN-9070).

Motion-SPMTMMCU

VDD

VTH

RTHADC Port

RTH

NTC

Figure 11. Temperature-Sensing Circuit by NTC Thermistor

Figure 11 is example of a temperature-sensing circuit by NTC thermistor. In this

reference design, RTHis 6.8kand Figure 12 is the V-T curve at RTH=6.8k,

VCC=3.3V, and VCC= 5.0V.


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20 30 40 50 60 70 80 90 100 110 1200

1

2

3

4

5

VDD

=3.3V

VDD

=5.0V

VOUT(min)

VOUT(typ)

VOUT(max)

V-T Curve at VDD

=5.0, 3.3V, RTH

=6.8kohm

Ou

tputVoltage

ofR

TH[

V]

Temperature TThermistor

[oC]

Figure 12. V-T Curve of Temperature-Sensing Circuit in Reference Design


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2.7. Print Circuit Board(PCB) Layout Guidance

Figure 13. PCB Layout Guidance


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3.Related Resources

FNA41560 Smart Power Module Motion-SPM

AN-9070 Smart Power Module Motion-SPM

in Mini DIP SPMUser Guide

AN-9071 Smart Power Module Motion-SPM in Mini DIP SPMThermal Performance Information

AN-9072-Smart Power Module Motion-SPMin Mini DIP SPMMounting Guidance

http://www.fairchildsemi.com/referencedesign/

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