®
ACST8
OVER VOLTAGE PROTECTED
AC POWER SWITCH
ASD™
(AC Switch Family)
MAIN APPLICATIONS
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■
■
AC static switching in appliance & industrial
control systems
Washing machine with bi-rotational induction
motor drive
Induction motor drive for:
- refrigerator / freezer compressor
- air conditioning compressor
OUT
G
OUT
COM
G
OUT
COM
FEATURES
■
■
■
■
■
■
V
DRM
/V
RRM
= +/- 800V
Avalanche controlled device
I
T(RMS)
= 8A with T
CASE
= 90 °C
High noise immunity: static dV/dt > 750 V/µs
Gate triggering current : I
GT
< 30 mA
Snubberless turn off commutation:
(dI/dt)c > 4.5A/ms
TO-220FPAB
ACST8-8CFP
OUT
TO-220AB
ACST8-8CT
G
COM
BENEFITS
■
■
■
■
D
2
PAK
ACST8-8CG
Enables equipment to meet EN61000-4-5
standard
High off-state reliability with planar technology
Need no external overvoltage protection
Reduces the power component count
Table 1: Order Codes
Part Number
ACST8-8CFP
ACST8-8CT
Marking
ACST88C
DESCRIPTION
The ACST8-8C belongs to the AC power switch
family built around the ASD
TM
technology. This
high performance device is adapted to home appli-
ances or industrial systems and drives an induc-
tion motor up to 8A.
This ACST switch embeds a triac structure with a
high voltage clamping device to absorb the induc-
tive turn off energy and withstand line transients
such as those described in the IEC61000-4-5
standards.
ACST8-8CG
Figure 1: Functional Diagram
OUT
G
COM
TM:
ASD is a trademark of STMicroelectronics.
November 2004
REV. 6
1/10
ACST8
Table 2: Absolute Ratings
(limiting values)
Symbol
I
T(RMS)
I
TSM
I
2
t
dI/dt
V
PP
T
stg
T
j
T
l
Parameter
TO-220FPAB
RMS on-state current full cycle sine
TO-220AB /
wave 50 to 60 Hz
D
2
PAK
Non repetitive surge peak on-state current
T
j
initial = 25°C, full cycle sine wave
Thermal constraint for fuse selection
Non repetitive on-state current critical rate of rise
I
G
= 10mA (t
r
< 100ns)
Non repetitive line peak pulse voltage
Storage temperature range
Operating junction temperature range
Maximum lead soldering temperature during 10s
Tcase = 90°C
Tcase = 100°C
t
p
= 20ms
t
p
= 16.7ms
tp = 10ms
Rate period > 1mn
note 1
Value
8
8
80
85
35
100
2
- 40 to + 150
- 40 to + 125
260
Unit
A
A
A
A
2
s
A/µs
kV
°C
°C
°C
Note 1:
according to test described by IEC61000-4-5 standard & figure A.
Table 3: Gate Characteristics
(maximum values)
Symbol
Parameter
Average gate power dissipation
P
G (AV)
P
GM
Peak gate power dissipation (t
p
= 20µs)
Peak gate current (t
p
= 20µs)
I
GM
Table 4: Thermal Resistance
Symbol
R
th(j-a)
R
th(j-a)
R
th(j-c)
R
th(j-c)
Junction to ambient
Parameter
Value
0.1
10
1
Unit
W
W
A
Value
60
45
3.5
2.5
Unit
°C/W
°C/W
°C/W
°C/W
TO-220FPAB
TO-220AB
Junction to ambien (soldered on 1 cm
2
copper pad) D
2
PAK
Junction to case for full cycle sine wave conduction TO-220FPAB
TO-220AB
Junction to case for full cycle sine wave conduction
2
D PAK
Table 5: Parameter Description
Parameter Symbol
I
GT
Gate triggering current
V
GT
Gate triggering voltage
V
GD
I
H
I
L
V
TM
V
T0
R
d
I
DRM
/ I
RRM
dV/dt
(dI/dt)c
V
CL
Non triggering voltage
Holding current
Latching current
On state voltage
Parameter description
On state characteristic threshold voltage
On state characteristic dynamic resistance
Forward or reverse leakage current
Static pin OUT voltage rise
Turn off current rate of decay
Avalanche voltage at turn off
2/10
ACST8
Table 6: Electrical Characteristics per Switch
For either positive or negative polary of pin OUT voltage respect to pin COM voltage
Symbol
V
DRM
/
V
RRM
I
GT
V
GT
V
GD
I
H
I
L
V
TM
V
T0
R
d
I
DRM
/
I
RRM
dV/dt
(dI/dt)c
V
CL
V
OUT
= V
DRM
V
OUT
= V
RRM
V
OUT
= 550V
Without snubber
I
CL
= 1mA
t
p
= 1ms
gate open
Test conditions
Repetitive peak off-state voltage
V
OUT
= 12V (DC) R
L
= 33Ω
V
OUT
= 12V (DC) R
L
= 33Ω
V
OUT
= V
DRM
I
OUT
= 100mA
I
G
= 20mA
I
OUT
= 11A
t
p
= 380µs
R
L
= 3.3kΩ
Gate open
T
j
= 25°C
T
j
= 25°C
T
j
= 125°C
T
j
= 25°C
T
j
= 25°C
T
j
= 25°C
T
j
= 125°C
T
j
= 125°C
T
j
= 25°C
T
j
= 125°C
T
j
= 125°C
T
j
= 125°C
T
j
= 25°C
MAX.
MAX.
MAX.
MIN.
MAX.
MAX.
MAX.
MAX.
MAX.
MAX.
MAX.
MIN.
MIN.
TYP.
Values
800
30
1.5
0.2
40
70
1.5
0.95
50
10
1
750
4.5
1200
Unit
V
mA
V
V
mA
mA
V
V
mΩ
µA
mA
V/µs
A/ms
V
1. AC LINE SWITCH BASIC APPLICATION
The ACST8-8C device is especially designed to drive medium power induction motors in washing ma-
chines, refrigerators, dish washers, and tumble dryers.
Pin COM
Pin G
Pin OUT
: Common drive reference, to be connected to the power line neutral
: Switch Gate input to be connected to the controller
: Switch Output to be connected to the load
When driven from a low voltage controller, the ACST switch is triggered with a negative gate current flow-
ing out of the gate pin G. It can be driven by the controller through a resistor as shown on the typical appli-
cation diagram. In appliance systems, the ACST8-8C switch intends to drive medium power load in ON /
OFF full cycle or phase angle control mode.
Thanks to its thermal and turn-off commutation characteristics, the ACST8-8C switch is able to drive an
inductive load up to 8A without a turn-off aid snubber circuit.
In washing machine or drier appliances, the tumble rotates in both directions. When using bidirectional
phase shift induction motor, two switches are connected on each side of the phase shift capacitor: in
steady-state operation, one switch only conducts energising the coils and defining the tumble direction.
3/10
ACST8
Figure 2: Typical Application Diagram
OUT
G
COM
CONTROL
UNIT
2. ROBUSTNESS AGAINST FAST CAPACITOR DISCHARGE
When parasitic transients or controller mis-operation occur, the blocked switch may turn on by spurious
switch firing. Since the phase shift capacitor is charged, its energy is instantaneously dissipated through
the two ACSTs which can be destroyed. To prevent such a failure, a resistive inductive circuit R-L is added
in series with the phase shift capacitor.
The dI/dt depends on the maximal voltage V
max
of the phase shift capacitor (700V on 240V mains appli-
cations), and on the inductance L:
v
max
dl
L
dt
The total switch turn on di/dt is the sum of the di/dt created by any RC noise suppressor discharge and
the dI/dt created by the motor capacitor discharge.
Since the maximal dI/dt capability at turn-on of the ACST8 is 100A/µs, the motor capacitor di/dt is assumed
to be less than 50A/µs; therefore, the inductance should be 14µH.
The resistor R limits the surge current through the ACST8 during the capacitor discharge according to the
specified curve I
TSM
= f (tp) as shown in figure 11
(to be issued),
and 1.2Ω is low enough to limit the resistor
dissipation (usually less than 1 W).
Finally both the 14µH inductance and the 1.2Ω resistance provide a safety margin of two on the surge cur-
rent I
TSM
described in figure 11.
---- = ----------
-
M
VAC
C
L
R
Fast capacitor discharge when
one ACST switch turns on (T2)
and the motor runs (T1 ON).
700V
T1
ON
T2
4/10
ACST8
3. AC LINE TRANSIENT VOLTAGE RUGGEDNESS
The ACST8-8C switch is able to safely withstand the AC line transient voltages either by clamping the low
energy spikes or by breaking over under high energy shocks.
The test circuit in figure 3 is representative of the ACST application and is used to test the ACST switch
according to the IEC61000-4-5 standard conditions. Thanks to the load impedance, the ACST switch with-
stands voltage spikes up to 2 kV above the peak line voltage by breaking over safely. Such non repetitive
testing can be done 10 times on each AC line voltage polarity.
Figure 3: Overvoltage ruggedness test circuit for resistive and inductive loads according to
IEC61000-4-5 standard R = 47Ω, L = 10µH & V
PP
= 2kV
R
L
OUT
SURGE VOLTAGE
AC LINE & GENERATOR
V
AC
+ V
PP
G
COM
Figure 4: Maximum power dissipation versus
RMS on-state current
P(W)
11
10
9
8
7
6
5
4
3
2
1
0
0
1
2
3
4
5
6
7
8
180°
α=180°
Figure 5: RMS on-state current versus case
temperature
I
T(RMS)
(A)
9
TO-220AB/D PAK
2
8
7
6
5
4
3
TO-220FPAB
α
α
2
1
0
0
25
50
75
100
125
α=180°
I
T(RMS)
(A)
T
C
(°C)
Figure 6: RMS on-state current versus ambient
temperature
I
T(RMS)
(A)
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
25
50
α=180°
Printed circuit board FR4
Natural convection
Figure 7: Relative variation of thermal
impedance versus pulse duration (TO-220FPAB)
K=[Z
th
/R
th
]
1.E+00
Z
th(j-c)
D PAK
2
1.E-01
Z
th(j-a)
TO-220FPAB/TO-220AB
1.E-02
T
amb
(°C)
75
100
125
t
p
(°C)
1.E-03
1.E-03
1.E-02
1.E-01
1.E+00
1.E+01
TO-220FPAB
1.E+02
1.E+03
5/10
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