Datasheet

UAA2016
http://onsemi.com
3
Load
C
F
MAC212A8
R
out
8
5
R
sync
V
EE
V
ref
Temp. Red.
R
def
Hys
Adj
S2
R
S
Figure 1. Application Schematic
R
1
Synchronization
+
1
S1
R
2
4
R
3
−
11−Bit Counter
4−Bit DAC
3
UAA2016
1/2
Failsafe
Pulse
Amplifier
Sampling
Full Wave
Logic
Internal
Reference
Supply
Voltage
2
+V
CC
7
Output
6
R
S
Sync
+
++
Sense Input
NTC
220 Vac
APPLICATION INFORMATION
(For simplicity, the LED in series with R
out
is omitted in
the following calculations.)
Triac Choice and R
out
Determination
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
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
The load current is then:
I
Load
+ (Vrms 2
Ǹ
sin(2pft)–V
TM
)ńR
L
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
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.)