TSM1011 STMicroelectronics, TSM1011 Datasheet - Page 5

• Manufacturer Part Number: TSM1011
• Description: Constant Voltage and Constant Current Controller
• Manufacturer: STMicroelectronics

Voltage and Current Control
5
5.1 Voltage Control
The voltage loop is controlled via a first
transconductance
resistor bridge R
is directly connected to the output.
The relative values of R
chosen in accordance with
where V
To avoid discharge of the load, the resistor bridge
R
of application, a total value of 100k
would be appropriate for the resistors R
For example, if R
V
Note: If the low drop diode is to be inserted between the
5.2 Current control
The current loop is controlled via the second
transconductance operational amplifier, the sense
resistor R
V
resistor bridge tied to the V
Its midpoint is tied to the positive input of the
current control operational amplifier, and its foot is
to be connected to lower potential point of the
sense resistor, as shown in
resistors of this bridge are matched to provide the
best precision possible.
The control equation verifies that:
ref
sense
1
, R
R
V
R 1
=2.5V, then R
VOLTAGE AND CURRENT CONTROL
sense
sense
2
load and the voltage regulation resistor bridge to
avoid current flowing from the load through the
resistor bridge, this drop should be taken into
account in the above calculations by replacing
V
should have high impedance. For this type
=
out
threshold is achieved externally by a
out
sense
R
by (
is the desired output voltage.
=
2
I
lim
V
R
, and the optocoupler.
out
-------------------------- -
V
5
1
=
1
, R
out
+ V
= 41.9K .
------------------- -
R
V
2
V
operational
2
4
–
ref
V
, and the optocoupler which
drop
sense
= 100k , V
+
V
ref
).
ref
R
5
1
Equation 1
ref
and R
voltage reference.
amplifier,
Figure 3
out
2
:
Equation 1
Equation 2
should be
1
(or more)
= 4.10V,
and R
. The
the
2
.
where I
V
control loop.
Note that the R
taking into account the maximum dissipation
(P
Therefore, for most adapter and battery charger
applications, a quarter-watt, or half-watt resistor to
make the current sensing function is sufficient.
The
transconductance
common (to the output of the IC). This makes an
ORing function which ensures that whenever the
current or the voltage reaches too high values, the
optocoupler is activated.
The relation between the controlled current and
the controlled output voltage can be described
with a square characteristic as shown in the
following V/I output-power graph.
Fig. 3: Output voltage versus output current
sense
lim
0
) through it during full load operation.
TSM1011 Vcc : independent power supply
Secondary current regulation
current
I
Vout
lim
is the threshold voltage for the current
lim
P
lim
=
is the desired limited current, and
Voltage regulation
TSM1011 Vcc : On power output
Primary current regulation
----------------------------------------------- -
=
R
sinking
sense
4
V
+
se nse
R
operational
R
5
resistor should be chosen
5
V
outputs
ref
R
I
lim
sense
amplifiers
of
Equation 3
Equation 2’
TSM1011
the
Iout
two
are
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