IRF IR2277S

Data Sheet No. PD60233 revB
IR2277S/IR2177S(PbF)
Phase Current Sensor IC for AC motor control
Features
• Floating channel up to 600 V for IR2177 & 1200 V for
Product Summary
VOFFSET (max)
IR2277
•
•
•
•
•
•
•
IR2277
1200 V
IR2177
600 V
Vin range
±250mV
Bootstrap supply range
8-20 V
2.2 mA
Fast Over Current detection
Floating channel quiescent
current (max)
Sensing latency (max)
Suitable for bootstrap power supplies
Throughput
Synchronous sampling measurement system
High PWM noise (ripple) rejection capability
Digital PWM output
Low sensing latency (<7.5 µsec @20kHz)
Ratiometric analog output suitable for DSP A/D interface
Over Current threshold
(max)
7.5 µsec
(@20kHz)
40ksample/sec
(@20kHz)
±470 mV
Description
IR2177/IR2277 is a high voltage, high speed, single phase current
sensor interface for AC motor drive applications. The current is
sensed by an external shunt resistor. The IC converts the analog
voltage into a time interval through a precise circuit that also
performs a very good ripple rejection showing small group delay.
The time interval is level shifted and given to the output both as a
PWM signal (PO) and analog voltage (OUT). The analog voltage is
proportional to the measured current and is ratio metric with respect
to an externally provided voltage reference. The max throughput is
40 ksample/sec suitable for up to 20 kHz asymmetrical PWM
modulation and max delay is <7.5 µsec (@20kHz). Also a fast over
current signal is provided for IGBT protection.
Package
Typical Connection
(Please refer to
Lead Assignments
for correct pin
configuration. This
diagram shows
electrical
connections only)
1
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IR2277S/IR2177S(PbF)
Absolute Maximum Ratings
Absolute Maximum Ratings indicate sustained limits beyond which damage to the device may occur. All voltage parameters
are absolute voltages referenced to VSS, all currents are defined positive into any lead. The Thermal Resistance and Power
Dissipation ratings are measured under board mounted and still air conditions.
Symbol
Definition
VB
High Side Floating Supply Voltage
VS
Vin+ / VinG0 / G1
VCC
Sync
VRH/VRL
Out
PO
OC
dVS/dt
PD
RthJA
TJ
TS
TL
High Side Floating Ground Voltage
High-Side Inputs Voltages
High-Side Range Selectors
Low-Side Fixed Supply Voltage
Low-Side Input Synchronization Signal
DSP Reference High and Low Voltages
Analog Output Voltage
PWM Output
Over Current Output Voltage
Allowable Offset Voltage Slew Rate
Maximum Power Dissipation
Thermal Resistance, Junction to Ambient
Junction Temperature
Storage Temperature
Lead Temperature (Soldering, 10 seconds)
IR2277
IR2177
Min.
Max.
- 0.3
- 0.3
VB - 25
VS - 5
VS - 0.3
- 0.3
- 0.3
- 0.3
- 0.3
- 0.3
- 0.3
1225
625
VB + 0.3
VB + 0.3
VB + 0.3
25
VCC + 0.3
VCC + 0.3
VCC + 0.3
VCC + 0.3
VCC + 0.3
50
250
90
125
150
300
-40
-55
Units
V
V
V
V
V
V
V
V
V
V
V/ns
mW
ºC/W
ºC
ºC
ºC
Recommended Operating Conditions
For proper operation the device should be used within the recommended conditions. All voltage parameters are absolute
voltages referenced to Vss. The Vs offset rating is tested with all supplies biased at 15V differential.
Symbol
VBS
Definition
High Side Floating Supply Voltage (VB- VS)
VS
High Side Floating Ground Voltage
Vin+ / VinG0 / G1
VCC
Sync
fsync
High-Side Inputs Voltages
High-Side Range Selectors
Low Side Logic Fixed Supply Voltage
Low-Side Input Synchronization Signal
Sync Input Frequency
PO
OC
VRH
VRL
TA
PWM Output
Over Current Output Voltage
OUT Reference High Voltage
OUT Reference Low Voltage
Ambient Temperature
Note 1: Shorted to VS or VB
Note 2: Pull-Up Resistor to VCC
2
IR2277
IR2177
Using PO
Using OUT
Min.
Max.
Units
VS + 8.0
VS + 20
1200
600
VS + 5.0
Note1
20
VCC
20
20
Note 2
Note 2
VCC-2.5
VRH-3
125
V
-5
VS - 5.0
Note 1
8
VSS
4
8
-0.3
-0.3
3
VSS
-40
V
V
V
V
kHz
V
V
V
V
ºC
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IR2277S/IR2177S(PbF)
Static Electrical Characteristics
VCC, VBS = 15V unless otherwise specified. Temp=27°C; Vin=Vin+ - Vin.
Pin: VCC, VSS, VB, VS
Symbol
Definition
IQBS
Quiescent VBS supply current
IQCC
Quiescent VCC supply current
ILK
Offset supply leakage current
Min.
Typ.
Max.
Units
Test
Conditions
1
2.2
mA
fsync = 10kHz,
20kHz
6
mA
IR2277
50
IR2177
50
fsync = 10kHz,
20kHz
VB = VS =
1200V
µA
VB = VS = 600V
Pin: Vin+, Vin-, Sync, G0, G1, OC
Symbol
Definition
Min.
Typ.
Max.
250
-250
Vinmax
Vinmin
VIH
Maximum input voltage before saturation
Minimum input voltage before saturation
Sync Input High threshold
VIL
Sync Input Low threshold
Vhy
Sync Input Hysteresis
0.2
Ivinp
Vin+ input current
-18
-6
µA
Ipu
G0, G1 pull-up Current
-20
-8
µA
|Vocth|
RSync
Over Current Activation Threshold
SYNC to VSS internal pull-down
300
6
470
12
mV
kΩ
RonOC
Over Current On Resistance
25
75
Ω
2.2
0.8
Test
Conditions
Units
mV
mV
V
V
See Figure 1
See Figure 1
V
See Figure 1
fsync = 4kHz to
20kHz
G1, G0 = VB5V
@ I = 2mA
See Figure 3
Schmitt trigger
SYNC
Rsync
VIL
VIH
VSS
Vhy
Figure 1: Sync input thresholds
Figure 2: Sync input circuit
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IR2277S/IR2177S(PbF)
Pin: PO
Symbol
Definition
Min.
Typ.
VPOs
Input offset voltage measured by PWM
output
∆VPOs /
∆Tj
Input offset voltage temperature drift
∆VPOs
∆offset between samples on channel1
and channel2 measured at PO (See
Note1)
-10
Gp
PWM Output Gain
-38
∆Gp / ∆Tj
PWM Output Gain Temperature Drift
CMRR
PO
PO Output common mode (VS) rejection
0.2
VPOlin
PO Linearity
0.07
-50
-40.5
mV
Rpull-up=500 Ω
fsync = 4, 20kHz
Vthreshold=2.75V
Ext supply=5V
(See Figure 6)
mV
fsync = 10kHz
See Figure 6
-42.5
%/V
Vin=±250mV
%/(V*ºC)
m%/V
0.2
0.8
1.6
0.2
PO On Resistance
Test
Conditions
10
TBD
PO threshold for OC reset
Units
µV/°C
TBD
PSRR PO PSRR for PO Output
RonPO
20
TBD
∆ Vlin/ ∆Tj PO Linearity Temperature Drift
VthPO
Max.
25
75
Vs-Vss = 0,
600V
fsync = 10kHz
%
10kHz
%/ºC
10kHz
OC active (See
Figure 4)
V
%/V
Ω
VCC=VBS=
8,20V
@ I = 2mA
See Figure 3
Note1: Refer to PO output description for channels definition
PO
or
OC
RON
VSS
Internal signal
Figure 3: PO and OC open collector circuit
4
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IR2277S/IR2177S(PbF)
Pin: OUT, VRH, VRL
Symbol
Definition
Min.
Typ.
RREF
VRH to VRL input resistance
36
Vaos
Input offset voltage measured by
analog output
-100
∆ Vaos /
∆Tj
Input offset voltage temperature drift
∆Vaos
∆offset between samples on channel1
and channel2 measured at OUT
(Note1)
Ga
Analog Output Gain
∆Ga / ∆Tj
Analog Output Gain Temperature Drift
TBD
CMRR
OUT
Analog Output common mode (VS
offset) rejection
100
VOUTlin
Out Linearity
0.3
∆ Vlin /
∆Tj
PSRR
OUT
Max.
Units
84
kΩ
50
TBD
mV
µV / ºC
Test
Conditions
fsync = 8kHz, 20
kHz
Measured by
analog output
fsync = 8kHz, 20
kHz
-20%
Out Linearity Temperature Drift
2VR
+20%
V/V
ºC
-1
dB
0.7
TBD
VR=VRH-VRL=3V
%
%/ºC
Vs-Vss=0V,
600V
fsync = 10kHz
fsync = 8kHz,
20kHz
fsync = 8kHz,
20kHz
VCC= VBS =8V,
20V
PSRR for Analog Output
30
100
dB
VOUTl
Vout Low Saturation
0
50
mV
Vin= -500mV
VOUTh
Vout High Saturation
VRH+0.2
VRH+0.7
V
Vin = +500mV
Note1: Refer to PO output description for channels definition
5
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IR2277S/IR2177S(PbF)
AC Electrical Characteristics
VBIAS (VCC, VBS) = 15V unless otherwise specified. Temp=27°C.
Symbol
Definition
fsync
PWM frequency
fout
Throughput
BW
Bandwidth (@ -3 dB)
GD
Group Delay (input filter)
Dmin
Min.
Typ.
Max.
PO
4
20
OUT
8
20
Units
Test
Conditions
kHz
2 ⋅ f sync
ksample/sec
f sync
kHz
1
4 ⋅ f sync
µs
Minimum Duty Cycle (Note 1)
10
%
Vin=+Vinmax
Dmax
Maximum Duty Cycle (Note 1)
30
%
Vin=-Vinmin
tdOCon
De-bounce time of OC
4.7
µs
See Figure 4
TOCoff
Time to reset OC forcing PO
0.5
µs
See Figure 4
Cload
Analog output load capacitor
0
50
nF
NOTE 2
SLOUT
tsettl
Analog output (OUT) Slew Rate
Output settling time (1%)
0.2
5
V/µs
µs
Cout ≤ 5 nF
Cout ≤ 5 nF
MD
Measure Delay
1
30
0.30
2 ⋅ f sync
SR
Step response (max time to reach
steady state) for PO output
SROUT
Step response (max time to reach
steady state) for OUT output
2.7
3.5
µs
See
0.51
f sync
1. 3
f sync
µs
0.51
+ t settl
f sync
1 .3
+ t settl
f sync
µs
Figure 5
See
Figure 5
Note 1: negative logic, see Figure 4 on page 7
Note 2: Cload < 5 nF avoids overshoot
6
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IR2277S/IR2177S(PbF)
Figure 4: OC timing diagram
Vmax
Vin
Vmin
SYNC
PO
SR
(PO full response time)
VRH
MD
OUT
tsettl
VRL
SROUT
(OUT full response time)
Figure 5: timing diagram
7
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IR2277S/IR2177S(PbF)
Vmax
Vin
Vmin
SYNC
Supply=5V
PO
Vth=2.75V
GP *VPOs1
20%
GP *VPOs1
GP *VPOs0
20%
20%
GP *VPOs0
20%
DVPOs= VPOs1-VPOs0
Figure 6: ∆offset between two consecutive samples measured at PO
8
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IR2277S/IR2177S(PbF)
Lead Assignments
SOIC16WB
Lead Definitions
9
Pin
Symbol
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
VCC
OUT
VSS
VRL
VRH
OC
PO
Sync
NC
NC
G0
G1
VS
VINVIN+
VB
Description
Low side voltage supply
Analog output
Low side ground supply
Lower rail of A/D voltage range
Higher rail of A/D voltage range
Over current signal (open drain)
PWM output (open drain)
DSP synchronization signal
No connection
No connection
Integrator gain lsb
Integrator gain msb
High side return
Negative sense input
Positive sense input
High side supply
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IR2277S/IR2177S(PbF)
Timing and logic state diagrams description
** See OC and PO detailed descriptions below in this document
Functional block diagram
10
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IR2277S/IR2177S(PbF)
1
Device Description
1.1 SYNC input
Sync input clocks the whole device. In order to
make the device work properly it must be
synchronous with the triangular PWM carrier as
shown in Figure 8.
SYNC pin is internally pulled-down (10 kΩ) to VSS.
1.2 PWM Output (PO)
PWM output is an open collector output (active low).
It must be pulled-up to proper supply with an
external resistor (suggested value between 500Ω
and 10kΩ).
τ
Supply
Vlow
Figure 7: PO rising and falling slopes
PO pull-up resistor determines the rising slope of
the PO output and the lower value of PO as shown
in Figure 7, where τ = RC , C is the total PO pin
capacitance and R is the pull-up resistance.
Vlow
Ron
= Supply ⋅
R on + R pull −up
where Ron is the internal open collector resistance
and Rpull-up is the external pull-up resistance.
PO duty cycle is defined for active low logic by the
following formula:
Eq. 1
Dn =
Toff _ cycle _ n +1
Tcycle _ n
PO duty cycle (Dn) swings between 10% and 30%.
Zero input voltage corresponds to 20% duty cycle.
11
A residual offset can be read in PO duty cycle
according
to
VPOs
(see
Static
electrical
characteristics).
According to
Figure 8, it can be assumed that odd cycles are
represented by SYNC at high level (let’s name
channel 1 the output related to this state of SYNC)
and even cycles represented by SYNC at low level
(channel 2).
The two channels are independent in order to
provide the correct duty cycle value of PO even for
non-50% duty cycle of SYNC signal. Small variation
of SYNC duty cycle are then allowed and
automatically corrected when calculating the duty
cycle using Eq. 1.
However, channel 1 and channel 2 can have a
difference in offset value which is specified in
∆VPOS (see Static electrical characteristics).
To implement a correct offset compensation of PO
duty cycle and analog OUT, each channel must be
compensated separately.
1.3 Over Current output (OC)
OC output is an open drain pin (active low).
A simplified block diagram of the over current circuit
is shown in the
Figure 9.
Over current is detected when |Vin|=|Vinp-Vinm|>VOCth.
If an event of over current lasts longer than tdOCon,
OC pin is forced to VSS and remains latched until
PO is externally forced low for at least tOCoff (see
timing on Figure 4). During an over current event
(OC is low), PO is off (pulled-up by external
resistor).
If OC is reset by PO and over current is still active,
OC pin will be forced low again by the next edge of
SYNC signal.
To reset OC state PO must be forced to VSS for at
least TOCoff.
• Autoreset function
The autoreset function consists in clearing
automatically the OC fault.
To enable the autoreset function, simply short
circuit the OC pin with the PO pin.
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IR2277S/IR2177S(PbF)
Cycle 1
Cycle 2
Cycle 3
Cycle 4
Triangular
SYNC (0)
PO
Toff_cycle1
Tcycle1
Dn1 =
Toff_cycle2
Toff _ cycle2
Tcycle2
Tcycle1
Dn2 =
Toff_cycle3
Toff _ cycle3
Tcycle2
Tcycle3
Dn3 =
Toff_cycle4
Toff _ cycle4
Tcycle3
Figure 8: PO Duty Cycle
H igh voltage
V IN +
V IN -
O ver current
detection
Level shifter
E xt
supply
Low voltage
S
D
OC
V SS
R
PO
Figure 9: Over current block diagram
12
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IR2277S/IR2177S(PbF)
1.4 Analog Output (OUT)
The analog output is internally buffered and capable
of driving capacitive loads ranging up to 50nF.
VRH and VRL set the dynamic range and gain of OUT
pin.
Additional circuitry to protect A/D converter input
against excessive voltage is not required.
Hereafter follow some definitions (see Figure 10
and following).
•
•
Vin=Vinp-Vinm
Input referred analog offset (Vaos): It is
the input that gives an output that equals
V RH + V RL
(referred to VSS).
2
∆OUT
Gain: It is defined by the ratio Ga=
.
∆Vin
OUT
VRH
VRH+VRL
2
VRL
Vin
VSS
Vaos
OUT =
•
•
Linearity: It is defined by the maximum
difference between the ideal OUT/Vin curve
and the measured curve depurated of the
offset voltage and the gain error.
Figure 10: Input offset definition
OUT
VRH
OUT
The analog output is also defined by some dynamic
characteristics (see figure 8):
•
•
•
•
Slew Rate (SLOUT). The maximum slope of
OUT measured in V/µs
Settling time (tsettl). Time needed by the
analog output (OUT) to reach 90% of final
value.
Measure delay (MD). It is defined by the
time interval between the actual SYNC
edge and PO rising edge.
Step response (SR). Is the time needed by
Output to reach the final value after a step
of the input.
Is always within the following range:
(Vpos if PO is measured
instead of OUT)
Ga
Gid
VRL
Vin
Vin
VSS
Figure 11: Gain definition
OUT
VRH
Linearity
Error
1
1
+ MD + t settl ≤ SROUT ≤
+ MD + t settl
2 ⋅ f SYNC
f SYNC
Ga
Gid
VRL
Vin
VSS
Figure 12: Linearity error definition
13
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IR2277S/IR2177S(PbF)
1.5 DC transfer functions
Eq. 3
The working principle of the device can be easily
explained by Figure 13, in which the main signals
are represented.
Triangular
reference
OUT = 2 ⋅ (VRH − VRL ) ⋅ Vin +
The same equation can be referred to VRL, as
follows in Eq. 4:
Eq. 4
OUT − VRL = 2 ⋅ (VRH − VRL ) ⋅ Vin +
SYNC
VRH + VRL
2
OUT
Vin
VRH − VRL
2
VRH
PO
VRH
OUT
(VRH+VRL)/2
VRL
Figure 13: Main current sensor signals and
outputs
Eq. 2 Dn = 20% − 40
200mV
100mV
0mV
-100mV
-200mV
250mV
Vin
VRL
-250mV
PWM out (PO pin) gives a duty cycle which is
inversely proportional to the input signal while the
OUT pin gives the analog converted output.
Eq. 2 gives the resulting Dn of the PWM output (PO
pin):
Figure 15: ideal OUT/Vin transfer function
%
⋅ Vin
V
where Vin = Vinp-Vinm
PO duty cycle
30%
25%
20%
15%
10%
Vin
Figure 14: PO Duty Cycle (Dn)
The Voltage-to-Time conversion (Vin to PO) must be
reconstructed (see Functional Block Diagram) to
give an analog voltage output at OUT pin.
OUT pin swings from VRL to VRH, so the analog
output (referred to VSS) follows Eq. 3:
14
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IR2277S/IR2177S(PbF)
Filter AC characteristic
IR2177/2277 signal path can be considered as
composed by three stages in series (see Figure 17).
The first two stages perform the filtering action.
Stage 1 (input filter) implements the filtering action
originating the transfer function shown in Figure 18.
The input filter is a self-adaptive reset integrator
which performs an accurate ripple cancellation. This
stage extracts automatically the PWM frequency
from Sync signal and puts transmission zeros at
even harmonics, rejecting the unwanted PWM
noise.
The following timing diagram shows the principle by
which even harmonics are rejected (Figure 16).
As can be seen from Figure 18, the odd harmonics
are rejected as a first order low pass filter with a
single pole placed in fPWM.
The input filter group delay in the pass-band is very
low (see GD on AC electrical characteristics) due to
the beneficial action of the zeroes.
The second stage samples the result of the first
stage at double Sync frequency. This action can be
used to fully remove the odd harmonics from the
input signal.
To perform this cancellation it is necessary a shift of
90 degrees of the SYNC signal with respect to the
triangular carrier edges (SYNC2).
The following timing diagrams show the principle of
odd harmonics cancellation (Figure 19), in which
SYNC2 allows the sampling of stage 1 output
during odd harmonic zero crossings.
Odd harmonic cancellation using SYNC2 (i.e. 90
degree shifted SYNC signal) signal will introduce
Tsync/4 additional propagation delay.
Anther way to obtain the same result (odd
harmonics cancellation) can be achieved by
controller computing the average of two consecutive
PO results using SYNC1 (SYNC is in this case
aligned to triangular edges, i.e. 0 degree shift).
This method is suitable for most symmetric (center
aligned) PWM schemes.
For this particular PWM scheme another suitable
solution is driving the IR2x77 with a half frequency
SYNC signal (fsync=fPWM/2).
In this case the cut frequency of the input filter is
reduced by half allowing zeroes to be put at fPWM
multiples (i.e. even and odd harmonics cancellation,
no more computational effort needed by the
controller).
Figure 16: Even harmonic cancellation principle
Figure 17: Simplified block diagram
15
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IR2277S/IR2177S(PbF)
Figure 18: Input filter transfer function (10 kHz PWM)
16
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IR2277S/IR2177S(PbF)
Switching level
Triangular
Phase voltage
Phase current
Current Mean
Fundamental
harmonic
Third
harmonic
Stage 1 input:
Input signal
components
(1st and 2nd
harmonic only)
Fundamental
harmonic
Third
harmonic
SYNC 1
Error
SYNC 2
Stage 1
output
Sampling
instant
Sampling
instant
Figure 19: Even harmonic cancellation principle
G0 and G1 pins are used to change the time
constant of the integrators of the high side input
filter.
To avoid internal saturation of the input filter, G0
and G1 must be connect according to SYNC
frequency as shown in Table 1. A too small time
constant may saturate the internal integrator, while
a large time constant may reduce accuracy.
G0 and G1 do not affect the overall current sensor
gain.
f PWM
G0
G1
> 16 kHz *
VB
VB
16 / 10 kHz
VS
VB
10 / 6 kHz
VB
VS
< 6 kHz
VS
VS
*Æ 40 kHz
Table 1: G0, G1 gain settings
2
Sizing tips
2.1 Bootstrap supply
The VBS1,2,3 voltage provides the supply to the high
side drivers circuitry of the IR2277S/IR2177S. VBS
supply sit on top of the VS voltage and so it must be
floating.
The bootstrap method to generate VBS supply can
be used with IR2277S/IR2177S current sensors.
The bootstrap supply is formed by a diode and a
capacitor connected as in Figure 20.
IR2277S
or
IR2177S
1.6 Input filter gain setting
Figure 20: bootstrap supply schematic
17
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IR2277S/IR2177S(PbF)
This method has the advantage of being simple and
low cost but may force some limitations on dutycycle and on-time since they are limited by the
requirement to refresh the charge in the bootstrap
capacitor.
Proper capacitor choice can reduce drastically
these limitations.
Bootstrap capacitor sizing
Given the maximum admitted voltage drop for VBS,
namely ∆VBS, the influencing factors contributing to
VBS decrease are:
−
−
−
−
Floating section quiescent current (IQBS);
Floating section leakage current (ILK)
Bootstrap diode leakage current (ILK_DIODE);
Charge required by the internal level shifters
(QLS); typical 20nC
− Bootstrap capacitor leakage current (ILK_CAP);
− High side on time (THON).
ILK_CAP is only relevant when using an electrolytic
capacitor and can be ignored if other types of
capacitors are used. It is strongly recommend using
at least one low ESR ceramic capacitor (paralleling
electrolytic and low ESR ceramic may result in an
efficient solution).
Then we have:
QTOT = QLS + ( I QBS + + I LK + I LK _ DIODE + I LK _ CAP ) ⋅ THON
The minimum size of bootstrap capacitor is then:
C BOOT min =
QTOT
∆V BS
Some important considerations
a) Voltage ripple
There are three different cases making the
bootstrap circuit get conductive (see Figure 20)
‚ ILOAD < 0; the load current flows in the low side
IGBT displaying relevant VCEon
VBS = VCC − VF − VCEon
In this case we have the lowest value for VBS.
This represents the worst case for the bootstrap
capacitor sizing. When the IGBT is turned off the
Vs node is pushed up by the load current until the
18
high side freewheeling diode get forwarded
biased
‚ ILOAD = 0; the IGBT is not loaded while being
on and VCE can be neglected
VBS = VCC − VF
‚ ILOAD > 0; the load current flows through the
freewheeling diode
V BS = VCC − VF + VFP
In this case we have the highest value for VBS.
Turning on the high side IGBT, ILOAD flows into it
and VS is pulled up.
b) Bootstrap Resistor
A resistor (Rboot) is placed in series with the
bootstrap diode (see Figure 20) to limit the current
when the bootstrap capacitor is initially charged. We
suggest not exceeding some Ohms (typically 5,
maximum 10 Ohms) to avoid increasing the VBS
time-constant. The minimum on time for charging
the bootstrap capacitor or for refreshing its charge
must be verified against this time-constant.
c) Bootstrap Capacitor
For high THON designs where an electrolytic tank
capacitor is used, its ESR must be considered. This
parasitic resistance develops a voltage divider with
Rboot generating a voltage step on VBS at the first
charge of bootstrap capacitor. The voltage step and
the related speed (dVBS/dt) should be limited. As a
general rule, ESR should meet the following
constraint:
ESR
⋅ VCC ≤ 3V
ESR + RBOOT
Parallel combination of small ceramic and large
electrolytic capacitors is normally the best
compromise, the first acting as fast charge tank for
the gate charge only and limiting the dVBS/dt by
reducing the equivalent resistance while the second
keeps the VBS voltage drop inside the desired ∆VBS.
d) Bootstrap Diode
The diode must have a BV> 600V (or 1200V
depending on application) and a fast recovery time
(trr < 100 ns) to minimize the amount of charge fed
back from the bootstrap capacitor to VCC supply.
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IR2277S/IR2177S(PbF)
3
PCB LAYOUT TIPS
3.1 Distance from H to L voltage
The IR2277S/IR2177S package (wide body)
maximizes the distance between floating (from DCto DC+) and low voltage pins (VSS). It is strongly
recommended to place components tied to floating
voltage in the respective high voltage portions of the
device (VB, VS) side.
3.3 Antenna loops and inputs
connection
Current loops behave like antennas able to receive
EM noise. In order to reduce EM coupling loops
must be reduced as much as possible. Figure 21
shows the high side shunt loops.
Moreover it is strongly suggested to use Kelvin
connections for Vin+ and Vin- to shunt paths and starconnect VS to Vin- close to the shunt resistor as
explained in Fig. 22.
3.2 Ground plane
Ground plane must NOT be placed under or nearby
the high voltage floating side to minimize noise
coupling.
VB
VS
VB
V in V in +
VS
Vin-
Antenna
Loop
Vin+
Figure 22: Recommended shunt connection
Figure 21: antenna loops
3.4 Supply capacitors
The supply capacitors must be placed as close as
possible to the device pins (VCC and VSS for the
ground tied supply, VB and VS for the floating
supply) in order to minimize parasitic traces
inductance/resistance
19
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IR2277S/IR2177S(PbF)
Case Outline
WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245 Tel: (310) 252-7105
This part has been qualified for the Industrial Market
Data and specifications subject to change without notice. 8/18/2005
20
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