IES5521ATR Hendon Semiconductors, IES5521ATR Datasheet - Page 6

• Manufacturer Part Number: IES5521ATR
• Description: Board Mount Temperature Sensors 10mA Triac Temp control + Timer
• Manufacturer: Hendon Semiconductors

Specifications of IES5521ATR

• Package / Case: SO-8
• Supply Voltage (max): 7.6 V
• Supply Voltage (min): 6.3 V
• Maximum Operating Temperature: + 100 C
• Minimum Operating Temperature: - 25 C
• Supply Current: 210 uA
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

9
9.1
Figure 5 shows a typical simple circuit
for a load of greater than 400W. In this
application the PWR pin is not used.
The power supply resistance of
160 kΩ sets the DC power supply
current available for the operation of
the circuit. When it is required to fire
the triac the gate pulse width must be
sufficiently long to ensure that the
triac load current is greater than the
latching current when the gate pulse
is removed. Hence the need to
specify a minimum operating load for
this circuit. At the same time most of
the operating DC current derived
through the resistor is used in
providing the gate signal, thereby
putting a tight limit on the upper value
of the width of the gate pulse. The
width of the gate pulse is derived from
the supply voltage and the
instantaneous value of the current
flowing through the power supply
resistor.
In figure 6 an application circuit is
shown for a 60W load, using the PWR
pin as well as the AC input pin.
Using a BT134 600E triac for a 60W
load on 220V means an 805Ω load. At
20mA latching current (positive), then
the mains voltage for latching is 16V
(with a margin use 20V) at a phase
angle of 3.7 degrees. For 66µA in R3
when the mains voltage is 20V, then
The supply current at mains peak
voltage in R3 is
The negative latching current of the
BT134 600E is –15mA, giving a
mains voltage at this time of –15V.
Thus when the mains voltage is –15V,
from the ratio of R3 and R5, the
voltage on pin AC must be –6V.
Therefore R5 = 220kΩ, and the firing
angle 2.8 degrees.
2006 Sep 01, Revision 1.1
(
APPLICATION INFORMATION
220
Design considerations
×
R3
2
)
=
⁄
(
330kΩ
330k
)
=
943µA
.
The gate pulse width is 6.5 degrees,
with a duty cycle of 3.6%. That is
722µA average for a peak (cold plus
margin) gate current of – 20mA.
Therefore the average current
needed from the power supply is the
sum of the average gate current
(I
current (I
current averaged over the two half
cycles (I
current in the RC network
.
Of this
via R3, so R6 must supply a further
768 µA average through the PWR pin.
Therefore R6 is
A number of important characteristics
of the triac are temperature sensitive.
It is essential that the controlling
integrated circuit exhibits comparable
sensitivity to temperature change so
that its characteristics vary in the
same way as those of the triac,
ensuring proper triggering over the
full operating range.
9.2
A typical triac has a maximum
latching current for the negative half
cycle of 25 mA. If the gate pulse is
terminated when the supply voltage
falls below −6 volts, the minimum load
can be calculated for which the
holding current is reached before the
supply voltage falls to this value.
However, with the addition of
resistors to V
pin, other threshold voltages can be
achieved, allowing other loads.
9.3
A typical positive half cycle latching
current is 35 mA. Considering chip
resistor tolerances, and from the
value of the mains power supply
(
V
GATE-AVG
722
RCTU
220
+
Negative half cycle
Positive half cycle
943 π ⁄
270
AC-AVG
⁄
⁄
EE
R4
(
), the maximum supply
771
), the positive threshold
+
)
EE
66
----- -
2
), and the average
=
×
and V
:
+
π
300µA
6
Simple Zero-Crossing Triac Control
)
------------ -
470k
3.0
=
CC
91kΩ
Circuit with Adjustable Time-out
from the AC
=
is supplied
1071µA
resistor of 160 kΩ in figure 5 the end
of the gate pulse can be calculated
using the threshold current of
nominally 66 µA where the gate drive
is turned off.
9.4
In assuming a triac gate current of
10 mA minimum an on chip margin
has to be allowed for component
tolerances, and a suitable variation
with ambient temperature. Also it
must be realised that most of the
supply current is used in providing the
gate current.
Thus in characterising the IES5521A
the design has taken into account the
availability of suitably sensitive triacs,
and used this to employ design
figures enabling operation in specific
applications with minimum external
component count, and yet ensuring
reliable triggering and proper
operation over normal operating
temperature and supply voltage
conditions.
9.5
The application circuit in figure 6 is
the simplest configuration in which a
negative temperature coefficient
(NTC) thermistor or another resistive
sensing element can be used. Note
that at the low temperature end of the
potentiometer travel no sensing
signal is available at all. However
simple resistor networks are usually
needed to linearise the response of
the setting resistor against control
temperature, and can easily be
designed to allow for maximum and
minimum operating points.
Alternatively these might be set
mechanically by stops inherent in the
mechanical construction of the
product using the IES5521A.
Some applications require more
accurate control over a limited
temperature range; for example the
control of fish tank heaters or water
Gate current
Temperature sensing
IES5521A
Product Specification