T2117 ATMEL Corporation, T2117 Datasheet - Page 2

• Manufacturer Part Number: T2117
• Description: Standard Zero Crossing Switch, Low-cost Application
• Manufacturer: ATMEL Corporation

Pin Description
General Description
The integrated circuit T2117 is a triac controller for zero-
crossing mode. It is designed to control power in
switching resistive loads of mains supplies.
Information regarding supply sync. is provided at Pin 8
via resistor R
wave logic guarantees that complete mains cycles are
used for load switching.
A fire pulse is released when the inverting input of the
comparator is negative (Pin 4) with respect to the non-
inverting input (Pin 3) and internal reference voltage. A
ramp generator with free selectable duration can be
performed by capacitor C
used for open-loop control (figure 4), but also for applica-
tion with proportional band regulation (figure 11). Ramp
voltage available at capacitor C
emitter follower at Pin l. To maintain the lamp flicker
specification, ramp duration is adjusted according to the
controlling load. In practice, interference should be
avoided (temperature control). Therefore, a two-point
control is preferred to proportional control. One can use
internal reference voltage for simple applications. In that
case, Pin 3 is inactive and connected to Pin 7 (GND), see
figure 13.
T2117
2 (11)
Pin
1
2
3
4
5
6
7
8
NEGIN
POSIN
Ramp
C
Ramp
Symbol
NEGIN
POSIN
Output
C
Ramp
GND
V
Sync
Ramp
V
sync
S
1
2
3
4
. To avoid DC load on the mains, the full-
Figure 2. Pinning
Ramp output
Ramp capacitor
Non-inverting comparator input
Inverting comparator input
Supply voltage
Trigger pulse output
Ground
Voltage synchronization
T2117
2
at Pin 2. The ramp function is
2
is decoupled across the
Function
8
7
6
5
V
GND
Output
V
sync
S
Triac Firing Current (Pulse)
This depends on the triac requirement. It can be limited
with gate series resistance which is calculated as follows:
where:
V
I
I
t
T
Firing Pulse Width t
This depends on the latching current of the triac and its
load current. The firing pulse width is determined by the
zero-crossing detection which can be influenced with the
help of sync. resistance, R
p
Gmax
p
–1.6 V
G
R
–7.6 V
V
Gmax
t
Figure 4. Threshold voltage of the ramp at V
p
1
=
= Gate voltage
= Maximum gate current
= Average gate current
= Firing pulse width
= Mains period duration
R
 7.5 V – V
4
w
2
Figure 3. Pin 1 internal network
arc. sin
I
I
1
Gmax
P
=
–V
I
Gmax
S
T
Gmax
T
I
L
sync
P 2
2
p
, (figure 6).
– 36 W
t
V
p
(Figure 5)
M
t
C
Rev. A2, 17-Dec-01
2
T2117
control
Ramp
V
Final voltage
Initial voltage
V
min
max
S
= –8.8 V