Maximum ratings are those values beyond which device damage can occur. Maximum ratings applied to the device are individual stress limit
values (not normal operating conditions) and are not valid simultaneously. If these limits are exceeded, device functional operation is not implied,
damage may occur and reliability may be affected.
ELECTRICAL CHARACTERISTICS
(T
A
= 25°C, V
EE
= −7.0 V, voltages referred to Pin 7, unless otherwise noted.)
Characteristic
Supply Current (Pins 6, 8 not connected), (T
A
= − 20° to + 85°C)
Stabilized Supply Voltage (Pin 5), (I
CC
= 2.0 mA)
Reference Voltage (Pin 1)
Output Pulse Current (T
A
= − 20° to + 85°C), (R
out
= 60 W, V
EE
= − 8.0 V)
Output Leakage Current (V
out
= 0 V)
Output Pulse Width (T
A
= − 20° to + 85°C) (Note 1), (Mains = 220 Vrms, R
sync
= 220 kW)
Comparator Offset (Note 5)
Sensor Input Bias Current
Sawtooth Period (Note 2)
Sawtooth Amplitude (Note 6)
Temperature Reduction Voltage (Note 3), (Pin 4 Connected to V
CC
)
Internal Hysteresis Voltage, (Pin 2 Not Connected)
Additional Hysteresis (Note 4), (Pin 2 Connected to V
CC
)
Failsafe Threshold (T
A
= − 20° to + 85°C) (Note 7)
Symbol
I
CC
V
EE
V
ref
I
O
I
OL
T
P
V
off
I
IB
T
S
A
S
V
TR
V
IH
V
H
V
FSth
Min
−
−10
−6.5
90
−
50
−10
−
−
50
280
−
280
180
Typ
0.9
−9.0
−5.5
100
−
−
−
−
40.96
70
350
10
350
−
Max
1.5
−8.0
−4.5
130
10
100
+10
0.1
−
90
420
−
420
300
Unit
mA
V
V
mA
mA
ms
mV
mA
sec
mV
mV
mV
mV
mV
1. Output pulses are centered with respect to zero crossing point. Pulse width is adjusted by the value of R
sync
. Refer to application curves.
2. The actual sawtooth period depends on the AC power line frequency. It is exactly 2048 times the corresponding period. For the 50 Hz case
it is 40.96 sec. For the 60 Hz case it is 34.13 sec. This is to comply with the European standard, namely that 2.0 kW loads cannot be connected
or removed from the line more than once every 30 sec. The inertia of most heating systems combined with the UAA2016 will comply with
the European Standard.
3. 350 mV corresponds to 5°C temperature reduction. This is tested at probe using internal test pad. Smaller temperature reduction can be
obtained by adding an external resistor between Pin 4 and V
CC
. Refer to application curves.
4. 350 mV corresponds to a hysteresis of 5°C. This is tested at probe using internal test pad. Smaller additional hysteresis can be obtained
by adding an external resistor between Pin 2 and V
CC
. Refer to application curves.
5. Parameter guaranteed but not tested. Worst case 10 mV corresponds to 0.15°C shift on set point.
6. Measured at probe by internal test pad. 70 mV corresponds to 1°C. Note that the proportional band is independent of the NTC value.
7. At very low temperature the NTC resistor increases quickly. This can cause the sensor input voltage to reach the failsafe threshold, thus inhibiting
output pulses; refer to application schematics. The corresponding temperature is the limit at which the circuit works in the typical application.
By setting this threshold at 0.05 V
ref
, the NTC value can increase up to 20 times its nominal value, thus the application works below − 20°C.
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2
UAA2016
S2
R
S
S1
R
def
R
2
R
1
R
3
3
Sense Input
4
Failsafe
+
−
Sampling
Full Wave
Logic
UAA2016
MAC212A8
Pulse
Amplifier
6
R
out
Output
220 Vac
Load
7
+V
CC
C
F
NTC
Temp. Red.
+
+
+
1/2
Internal
Reference
4−Bit DAC
2
Hys
Adj
11−Bit Counter
1
V
ref
Sync
R
sync
8
V
EE
R
S
5
Synchronization
Supply
Voltage
Figure 1. Application Schematic
APPLICATION INFORMATION
(For simplicity, the LED in series with R
out
is omitted in
the following calculations.)
Triac Choice and R
out
Determination
The load current is then:
I
Load
+
(Vrms
2
sin(2pft)–V
) R
TM
L
Depending on the power in the load, choose the triac that
has the lowest peak gate trigger current. This will limit the
output current of the UAA2016 and thus its power
consumption. Use Figure 4 to determine R
out
according to
the triac maximum gate current (I
GT
) and the application
low temperature limit. For a 2.0 kW load at 220 Vrms, a good
triac choice is the ON Semiconductor MAC212A8. Its
maximum peak gate trigger current at 25°C is 50 mA.
For an application to work down to − 20°C, R
out
should be
60
W.
It is assumed that: I
GT
(T) = I
GT
(25°C)
exp (−T/125)
with T in
°C,
which applies to the MAC212A8.
Output Pulse Width, R
sync
where V
TM
is the maximum on state voltage of the triac, f is
the line frequency.
Set I
Load
= I
Latch
for t = T
P
/2 to calculate T
P
.
Figures 6 and 7 give the value of T
P
which corresponds to
the higher of the values of I
Hold
and I
Latch
, assuming that
V
TM
= 1.6 V. Figure 8 gives the R
sync
that produces the
corresponding T
P
.
R
Supply
and Filter Capacitor
The pulse with T
P
is determined by the triac’s I
Hold
, I
Latch
together with the load value and working conditions
(frequency and voltage):
Given the RMS AC voltage and the load power, the load
value is:
R
L
= V
2
rms/POWER
With the output current and the pulse width determined as
above, use Figures 9 and 10 to determine R
Supply
, assuming
that the sinking current at V
ref
pin (including NTC bridge
current) is less than 0.5 mA. Then use Figure 11 and 12 to
determine the filter capacitor (C
F
) according to the ripple
desired on supply voltage. The maximum ripple allowed is
1.0 V.
Temperature Reduction Determined by R
1
(Refer to Figures 13 and 14.)
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UAA2016
Proportional Band
Room
Temperature
T (°C)
Overshoot
Time (minutes, Typ.)
Time (minutes, Typ.)
Heating
Power
P(W)
Time (minutes, Typ.)
Proportional Temperature Control
D
Reduced Overshoot
D
Good Stability
Time (minutes, Typ.)
ON/OFF Temperature Control
D
Large Overshoot
D
Marginal Stability
Figure 2. Comparison Between Proportional Control and ON/OFF Control
T
P
is centered on the zero−crossing.
T
P
AC Line
Waveform
I
Hold
I
Latch
Gate Current
Pulse
T
+
P
14 x Rsync
)
7
Vrms
2 x
p
f
105
(μs)
f = AC Line Frequency (Hz)
Vrms = AC Line RMS Voltage (V)
R
sync
= Synchronization Resistor (W)
Figure 3. Zero Voltage Technique
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4
UAA2016
CIRCUIT FUNCTIONAL DESCRIPTION
Power Supply (Pin 5 and Pin 7)
Sawtooth Generator
The application uses a current source supplied by a single
high voltage rectifier in series with a power dropping
resistor. An integrated shunt regulator delivers a V
EE
voltage of − 8.6 V with respect to Pin 7. The current used by
the total regulating system can be shared in four functional
blocks: IC supply, sensing bridge, triac gate firing pulses and
zener current. The integrated zener, as in any shunt
regulator, absorbs the excess supply current. The 50 Hz
pulsed supply current is smoothed by the large value
capacitor connected between Pins 5 and 7.
Temperature Sensing (Pin 3)
The actual temperature is sensed by a negative
temperature coefficient element connected in a resistor
divider fashion. This two element network is connected
between the ground terminal Pin 5 and the reference voltage
− 5.5 V available on Pin 1. The resulting voltage, a function
of the measured temperature, is applied to Pin 3 and
internally compared to a control voltage whose value
depends on several elements: Sawtooth, Temperature
Reduction and Hysteresis Adjust. (Refer to Application
Information.)
Temperature Reduction
In order to comply with European norms, the ON/OFF
period on the load must exceed 30 seconds. This is achieved
by an internal digital sawtooth which performs the
proportional regulation without any additional components.
The sawtooth signal is added to the reference applied to the
comparator inverting input. Figure 2 shows the regulation
improvement using the proportional band action. Figure 4
displays a timing diagram of typical system performance
using the UAA2016. The internal sawtooth generator runs
at a typical 40.96 sec period. The output duty cycle drive
waveform is adjusted depending on the time within the
40.96 sec period the drive needs to turn on. This occurs when
the voltage on the sawtooth waveform is above the voltage
provided at the Sense Input.
Noise Immunity
The noisy environment requires good immunity. Both the
voltage reference and the comparator hysteresis minimize
the noise effect on the comparator input. In addition the
effective triac triggering is enabled every 1/3 sec.
Failsafe
For energy saving, a remotely programmable temperature
reduction is available on Pin 4. The choice of resistor R
1
connected between Pin 4 and V
CC
sets the temperature
reduction level.
Comparator
Output pulses are inhibited by the “failsafe” circuit if the
comparator input voltage exceeds the specified threshold
voltage. This would occur if the temperature sensor circuit
is open.
Sampling Full Wave Logic
When the noninverting input (Pin 3) receives a voltage
less than the internal reference value, the comparator allows
the triggering logic to deliver pulses to the triac gate. To
improve the noise immunity, the comparator has an
adjustable hysteresis. The external resistor R
3
connected to
Pin 2 sets the hysteresis level. Setting Pin 2 open makes a
10 mV hysteresis level, corresponding to 0.15°C. Maximum
hysteresis is obtained by connecting Pin 2 to V
CC
. In that
case the level is set at 5°C. This configuration can be useful
for low temperature inertia systems.
Two consecutive zero−crossing trigger pulses are
generated at every positive mains half−cycle. This ensures
that the number of delivered pulses is even in every case. The
pulse length is selectable by R
sync
connected on Pin 8. The
pulse is centered on the zero−crossing mains waveform.
Pulse Amplifier
The pulse amplifier circuit sinks current pulses from Pin
6 to V
EE
. The minimum amplitude is 70 mA. The triac is
then triggered in quadrants II and III. The effective output
current amplitude is given by the external resistor R
out
.
Eventually, an LED can be inserted in series with the Triac
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