NUS3046MN ON Semiconductor, NUS3046MN Datasheet - Page 5

• Manufacturer Part Number: NUS3046MN
• Description: Overvoltage Protection Ic With Integrated Mosfet
• Manufacturer: ON Semiconductor

Normal Operation
adapter provides power to the protection system so the
circuitry is only active when the adapter is connected. The
OVP monitors the voltage from the charger and if the
voltage exceeds the overvoltage threshold, V
signal drives the gate of the MOSFET to within 1.0 V of
V
from the load. The nominal time it takes to drive the gate to
this state is 400 nsec (1.0 msec maximum for gate
capacitance of < 12 nF). The CNTRL input can be used to
interrupt charging and allow the microcontroller to measure
the cell voltage under a normal condition to get a more
accurate measure of the battery voltage. Once the
overvoltage is removed, the MOSFET will be turned on
again.
the MOSFET.
•
•
Adjusting the Overvoltage Detection Point with
External Resistors
overvoltage threshold, V
divider with the tap at the IN pin. However, the input
impedance R
since it is several 10’s of kW (R
following equation shows the effects of R
Figure 2. Voltage divider input to adjust overvoltage
CC
Figure 1 illustrates a typical configuration. The external
There are two events that will cause the OVP to turn off
The separate IN and V
Voltage on IN Rises Above the Overvoltage Detection
Threshold
CNTRL Input is Driven to a Logic HIGH
, thus turning off the FET and disconnecting the source
V CC + V x (1 ) R 1 (R 2 R in ))
in
does play a significant role in the calculation
R
R
1
2
V
detection point
CC
CC
th
, upwards by adding a resistor
pins allow the user to adjust the
GND
I
N
in
= 54 kW typical). The
NUS3046
R
in
in
.
th
, the OUT
(eq. 1)
http://onsemi.com
5
which equates to:
So, as R
accordance to the ratio of R
this shift can be minimized. The following steps show this
procedure.
Designing around the Maximum Voltage Rating
Requirements, V(V
IN is 15 V. Therefore, care must be taken that the design does
not exceed this voltage. Normally, the designer shorts V
to IN, V(V
However, one must take care when adjusting the
overvoltage threshold.
the V(V
equals 30 V, therefore, one must ensure that:
voltage levels that are less than 15 V. If greater thresholds are
desired, ON Semiconductor offers the NCP3045 which can
withstand those voltages.
This shows that R
The maximum breakdown voltage between pins V
In Figure 2, the R1 resistor of the voltage divider divides
V(V
Where 0.5 = V(V
Therefore, the overvoltage threshold should be adjusted to
CC
(V CC , IN) + V CC * (R1 (R1 ) (R2
CC
in
, IN) worst case equals 15 V, and V
approaches infinity:
, IN) voltage to a given voltage threshold equal to:
CC
V CC + V x (1 ) R 1 R 2 ) R 1 R in )
V CC + V x (1 ) R 1 R 2)
, IN) is shorted to 0 V, so there is no issue.
R1 (R1 ) (R2
CC
CC
in
, IN)max/V
, IN)
shifts the V
1
/ R
R in )) t 0.5
in
CCmax
. However, if R
th
detection point in
CC
R in )))
worst case
1
<< R
(eq. 2)
(eq. 3)
CC
(eq. 4)
(eq. 5)
and
CC
in
,