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TSM1051CD-TSM1051CLT
CONSTANT VOLTAGE AND CONSTANT CURRENT CONTROLLER FOR BATTERY CHARGERS AND ADAPTORS
CONSTANT VOLTAGE AND CONSTANT CURRENT CONTROL�
LOW VOLTAGE OPERATION PRECISION INTERNAL VOLTAGE
REFERENCE LOW EXTERNAL COMPONENT COUNT CURRENT SINK OUTPUT STAGE�
EASY COMPENSATION LOW AC MAINS VOLTAGE REJECTION
DESCRIPTIONTSM1051 is a highly integrated solution for SMPS
applications requiring CV (constant voltage) and
CC (constant current) mode.
TSM1051 integrates one voltage reference, two
operational amplifiers (with ORed outputs -
common collectors), and a current sensing circuit.
The voltage reference combined with one
operational amplifier makes it an ideal voltage
controller, and the other low voltage reference
combined with the other operational amplifier
makes it an ideal current limiter for output low side
current sensing.
The current threshold is fixed, and precise.
The only external components are:
* a resistor bridge to be connected to the output of
the power supply (adapter, battery charger) to set
the voltage regulation by dividing the desired
output voltage to match the internal voltage
reference value.
* a sense resistor having a value and allowable
dissipation power which need to be chosen
according to the internal voltage threshold.
* optional compensation components (R and C).
TSM1051, housed in one of the smallest package
available, is ideal for space shrinked applications
such as adapters and battery chargers.
APPLICATIONS ADAPTERS BATTERY CHARGERS
ORDER CODE L = Tiny Package (SOT23-6) - only available in Tape & Reel (LT)
D = Small Outline Package (SO) - also available in Tape & Reel (DT)
PIN CONNECTIONS (top view)
TSM1051CONSTANT VOLTAGE AND CONSTANT CURRENT
CONTROLLER FOR BATTERY CHARGERS AND ADAPTORS
TSM1051
PIN DESCRIPTION
SOT23-6 Pinout
SO8 Pinout
ABSOLUTE MAXIMUM RATINGS
TSM1051
OPERATING CONDITIONS
ELECTRICAL CHARACTERISTICSTamb = 25°C and Vcc = +5V (unless otherwise specified)
If the voltage on VCTRL (the negative input of the amplifier) is higher than the positive amplifier input (Vref=1.210V), and it is increased
by 1mV, the sinking current at the output OUT will be increased by 3.5mA. The internal Voltage Reference is set at 1.210V (bandgap reference). The voltage control loop precision takes into account the cumulative
effects of the internal voltage reference deviation as well as the input offset voltage of the trans-conductance operational amplifier. The
internal Voltage Reference is fixed by bandgap, and trimmed to 0.5% accuracy at room temperature. When the positive input at ICTRL is lower than -200mV, and the voltage is decreased by 1mV, the sinking current at the output OUT will
be increased by 7mA. The internal current sense threshold is set to -200mV. The current control loop precision takes into account the cumulative effects of the
internal voltage reference deviation as well as the input offset voltage of the trans-conduction operational amplifier.
TSM1051In the above application schematic, the TSM1051 is used on the secondary side of a flyback adapter (or
battery charger) to provide an accurate control of voltage and current. The above feedback loop is made
with an optocoupler.
Figure 1 : Internal Schematic
Figure 2 : Typical Adapter or Battery Charger Application Using TSM1051
TSM1051
Figure 3 : Vref vs Ambient Temperature
Figure 4 : Vsense pin input bias current vs
Ambient Temperature
Figure 5 : Output short circuit current vs
Ambient Temperature
Figure 6 : Vsense vs Ambient Temperature
Figure 7 : Ictrl pin input bias current vs
Ambient Temperature
Figure 8 : Supply current vs Ambient
Temperature
1. Voltage and Current Control
1.1. Voltage ControlThe voltage loop is controlled via a first transcon-
ductance operational amplifier, the resistor bridge
R1, R2, and the optocoupler which is directly con-
nected to the output.
The relation between the values of R1 and R2
should be chosen as written in Equation 1.
R1 = R2 x Vref / (Vout - Vref) Eq1
Where Vout is the desired output voltage.
To avoid the discharge of the load, the resistor
bridge R1, R2 should be highly resistive. For this
type of application, a total value of 100KΩ (or
more) would be appropriate for the resistors R1
and R2.
As an example, with R2 = 100KΩ, Vout = 4.10V,
Vref = 1.210V, then R1 = 41.9KΩ.
Note that if the low drop diode should be inserted
between the load and the voltage regulation resis-
tor bridge to avoid current flowing from the load
through the resistor bridge, this drop should be
taken into account in the above calculations by re-
placing Vout by (Vout + Vdrop).
1.2. Current ControlThe current loop is controlled via the second
trans-conductance operational amplifier, the
sense resistor Rsense, and the optocoupler.
The control equation verifies:
Rsense x Ilim = Vsense eq2
Rsense = Vsense / Ilim eq2’
where Ilim is the desired limited current, and
Vsense is the threshold voltage for the current
control loop.
As an example, with Ilim = 1A, Vsense = -200mV,
then Rsense = 200mΩ.
Note that the Rsense resistor should be chosen
taking into account the maximum dissipation
(Plim) through it during full load operation.
Plim = Vsense x Ilim. eq3
As an example, with Ilim = 1A, and Vsense =
200mV, Plim = 200mW.
Therefore, for most adapter and battery charger
applications, a quarter-watt, or half-watt resistor to
make the current sensing function is sufficient.
Vsense threshold is achieved internally by a re-
sistor bridge tied to the Vref voltage reference. Its
middle point is tied to the positive input of the cur-
rent control operational amplifier, and its foot is to
be connected to lower potential point of the sense
resistor as shown on the following figure. The re-
sistors of this bridge are matched to provide the
best precision possible.
The current sinking outputs of the two trans-con-
ductance operational amplifiers are common (to
the output of the IC). This makes an ORing func-
tion which ensures that whenever the current or
the voltage reaches too high values, the optocou-
pler is activated.
The relation between the controlled current and
the controlled output voltage can be described
with a square characteristic as shown in the fol-
lowing V/I output-power graph.
Figure 9 : Output voltage versus output current
2. CompensationThe voltage-control trans-conductance operation-
al amplifier can be fully compensated. Both of its
output and negative input are directly accessible
for external compensation components.
An example of a suitable compensation network is
shown in Fig.2. It consists of a capacitor
Cvc1=2.2nF and a resistor Rcv1=470KΩ in series,
TSM1051PRINCIPLE OF OPERATION AND APPLICATION HINTS
