S1220PBID Datasheet, PDF (11/18 Pages) ON Semiconductor – Universal Voltage Monitors

V₄
Input V_S2
V₃
GND
Input -V_S1
V₁
V₂
Output V_CC
Voltage
Pins 5, 6 GND
MC34161, MC33161, NCV33161
V_Hys2
V_Hys1
LED `ON'
V<sub>CC</sub>
8
2.54V
1
Reference
-
R<sub>4</sub> <sup>7</sup>
++
-V<sub>S1</sub>
+
2.8V
6
R<sub>3</sub> 2 <sub>+</sub> -
1.27V
-
R2
++
V<sub>S2</sub>
+
R<sub>1</sub>
3+ <sub>-</sub>
1.27V
0.6V
5
4
The above figure shows the MC34161 configured as a positive and negative overvoltage detector. As the input voltage increases from ground, the LED will turn
‘ON’ when either −V<sub>S1</sub> exceeds V<sub>2</sub>, or V<sub>S2</sub> exceeds V<sub>4</sub>. With the dashed line output connection, the circuit becomes a positive and negative undervoltage detector.
As the input voltage decreases from the peak towards ground, the LED will turn ‘ON’ when either V<sub>S2</sub> falls below V<sub>3</sub>, or −V<sub>S1</sub> falls below V<sub>1</sub>.
For known resistor values, the voltage trip points are:
V<sub>1</sub>
+
R<sub>3</sub>
R<sub>4</sub>
(V<sub>th1</sub>
*
V<sub>ref</sub>)
)
V<sub>th1</sub>
V<sub>2</sub>
+
R<sub>3</sub>
R<sub>4</sub>
(V<sub>th1</sub>
*
V<sub>H1</sub>
*
V<sub>ref</sub>)
)
V<sub>th1</sub>
*
V<sub>H1</sub>
ǒ Ǔ V<sub>3</sub> + (V<sub>th2</sub> * V<sub>H2</sub>)
R<sub>2</sub>
R<sub>1</sub>
)
1
ǒ Ǔ V<sub>4</sub> + V<sub>th2</sub>
R<sub>2</sub>
R<sub>1</sub>
)
1
For a specific trip voltage, the required resistor ratio is:
R<sub>3</sub>
R<sub>4</sub>
+
(V<sub>1</sub> * V<sub>th1</sub>)
(V<sub>th1</sub> * V<sub>ref</sub>)
R<sub>3</sub>
R<sub>4</sub>
+
(V<sub>2</sub> * V<sub>th1</sub> ) V<sub>H1</sub>)
(V<sub>th1</sub> * V<sub>H1</sub> * V<sub>ref</sub>)
R<sub>2</sub>
R<sub>1</sub>
+
V<sub>4</sub>
V<sub>th2</sub>
*
1
R<sub>2</sub>
R<sub>1</sub>
+
V<sub>3</sub>
V<sub>th2</sub> *
V<sub>H2</sub>
*
1
Figure 22. Positive and Negative Overvoltage Detector
Input V<sub>S1</sub>
V<sub>2</sub>
V<sub>1</sub>
GND
V<sub>3</sub>
Input -V<sub>S2</sub>
V<sub>4</sub>
Output V<sub>CC</sub>
Voltage
Pins 5, 6 <sub>GND</sub>
V<sub>Hys1</sub>
V<sub>Hys2</sub>
LED `ON'
V_CC
8
2.54V
1
Reference
-
R₄
V_{S1 R3}
7
+
2+ _-
1.27V
++
2.8V
-
6
R₂
++
+
0.6V
R₁
3+ _-
1.27V
5
-V_S2
4
The above figure shows the MC34161 configured as a positive and negative undervoltage detector. As the input voltage decreases toward ground, the LED will
turn ‘ON’ when either V_S1 falls below V₁, or −V_S2 falls below V₃. With the dashed line output connection, the circuit becomes a positive and negative overvoltage
detector. As the input voltage increases from the ground, the LED will turn ‘ON’ when either V_S1 exceeds V₂, or −V_S1 exceeds V₁.
For known resistor values, the voltage trip points are:
ǒ Ǔ V₁ + (V_th1 * V_H1)
R₄
R₃
)
1
ǒ Ǔ V₂ + V_th1
R₄
R₃
)
1
V₃
+
R₁
R₂
(V_th
*
V_ref)
)
V_th2
V₄
+
R₁
R₂
(V_th
*
V_H2
*
V_ref)
)
V_th2
*
V_H2
For a specific trip voltage, the required resistor ratio is:
R₄
R₃
+
V₂
V_th1
*
1
R₄
R₃
+
V₁
V_th1 *
V_H1
*
1
R₁
R₂
+
V₄ ) V_H2 * V_th2
V_th2 * V_H2 * V_ref
R₁
R₂
+
V₃ * V_th2
V_th2 * V_ref
Figure 23. Positive and Negative Undervoltage Detector
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