TSM105
CONSTANT VOLTAGE AND CONSTANT CURRENT
CONTROLLER FOR BATTERY CHARGERS AND ADAPTORS
s
CONSTANT VOLTAGE AND CONSTANT
s
s
s
s
s
s
CURRENT CONTROL
LOW VOLTAGE OPERATION
PRECISION INTERNAL VOLTAGE REFER-
ENCE
LOW EXTERNAL COMPONENT COUNT
CURRENT SINK OUTPUT STAGE
EASY COMPENSATION
LOW AC MAINS VOLTAGE REJECTION
ORDER CODE
Part
Number
TSM105CLT
TSM105CD
Temperature
Range
0 to 85°C
0 to 85°C
Package
Marking
L
•
•
D
M105
TSM105
L =
Tiny Package (SOT23-5) - only available in Tape & Reel (LT)
D =
Small Outline Package (SO) - also available in Tape & Reel (DT)
DESCRIPTION
TSM105 is a highly integrated solution for SMPS
applications requiring CV (constant voltage) and
CC (constant current) mode.
TSM105 integrates one voltage reference, two
operational amplifiers (with ORed outputs - com-
mon collectors), and a current sensing circuit.
The voltage reference combined with one opera-
tional amplifier makes it an ideal voltage control-
ler, 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 on the output of
the power supply (adapter, battery charger) to set
the voltage regulation by dividing the desired out-
put voltage to match the internal voltage reference
value.
* a sense resistor whose value and allowable dis-
sipation power need to be chosen according to the
internal voltage threshold.
* optional compensation components (R and C).
TSM105, housed in one of the smallest package
available, is ideal for space shrinked applications
such as adapters and battery chargers.
APPLICATIONS
L
SOT23-5
(Plastic Package)
D
SO8
(Plastic Micropackage)
PIN CONNECTIONS
(top view)
1
1
2
3
SOT23-5
Vctrl
Vcc
Gnd
Out
Ictrl
4
5
2
3
4
SO8
Vctrl
Vcc
Nc
Nc
Gnd
Out
Ictrl
Nc
8
7
6
5
s
ADAPTERS
s
BATTERY CHARGERS
September 2001
1/9
TSM105
PIN DESCRIPTION
SOT23-5 Pinout
Name
Vcc
Gnd
Vctrl
Ictrl
Out
Pin #
5
2
1
4
3
Type
Power Supply
Power Supply
Analog Input
Analog Input
Current Sink Output
Function
Positive Power Supply Line
Ground Line. 0V Reference For All Voltages
Input Pin of the Voltage Control Loop
Input Pin of the Current Control Loop
Output Pin. Sinking Current Only
SO8 Pinout
Name
Vcc
Gnd
Vctrl
Ictrl
Out
NC
NC
NC
Pin #
2
8
1
6
7
3
4
5
Type
Power Supply
Power Supply
Analog Input
Analog Input
Current Sink Output
Function
Positive Power Supply Line
Ground Line. 0V Reference For All Voltages
Input Pin of the Voltage Control Loop
Input Pin of the Current Control Loop
Output Pin. Sinking Current Only
ABSOLUTE MAXIMUM RATINGS
Symbol
Vcc
Vi
Top
Tj
Rthja
Rthja
DC Supply Voltage
DC Supply Voltage
Input Voltage
Operating Free Air Temperature Range
Maximum Junction Temperature
Thermal Resistance Junction to Ambient SO8 package
Thermal Resistance Junction to Ambient SOT23-5 package
Value
14
-0.3 to Vcc
-55 to 125
150
130
250
Unit
V
V
°C
°C
°C/W
°C/W
2/9
TSM105
OPERATING CONDITIONS
Symbol
Vcc
DC Supply Conditions
Parameter
Value
2.8 to 12
Unit
V
ELECTRICAL CHARACTERISTICS
Tamb = 25°C and Vcc = +5V (unless otherwise specified)
Symbol
Parameter
Test Condition
Min
Typ
Max
Unit
Total Current Consumption
Icc
Total Supply Current - not taking the
output sinking current into account
Tamb
0 < Tamb < 85°C
1.05
1.2
2
mA
Voltage Control Loop
Gmv
Vref
Iibv
Transconduction Gain (Vctrl). Sink
Current Only
1)
Voltage Control Loop Reference
2)
Input Bias Current (Vctrl)
Tamb
0 < Tamb < 85°C
Tamb
0 < Tamb < 85°C
Tamb
0 < Tamb < 85°C
1
1.198
1.186
3.5
2.5
1.21
50
100
mA/mV
1.222
1.234
V
nA
Current Control Loop
Gmi
Vsense
Iibi
Transconduction Gain (Ictrl). Sink
Current Only
3)
Current Control Loop Reference
4)
Current out of pin ICTRL at -200mV
Tamb
0 < Tamb < 85°C
Iout = 2.5mA Tamb
0 < Tamb < 85°C
Tamb
0 < Tamb < 85°C
1.5
196
192
7
4
200
25
50
mA/mV
204
208
mV
µA
Output Stage
Vol
Ios
Low output voltage at 10 mA sinking
current
Output Short Circuit Current. Output to
Vcc. Sink Current Only
Tamb
Tamb
0 < Tamb < 85°C
200
27
35
50
mV
mA
1. 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.
2. 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 temperaure.
3. 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.
4. 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-conductance operational amplifier.
3/9
TSM105
Figure 1 :
Internal Schematic
Vcc
1.210V
+
-
Vctrl
Out
200mV
+
-
Gnd
Ictrl
Figure 2 :
Typical Adapter or Battery Charger Application Using TSM105
D
TSM105
Vcc
OUT+
R2
Cvc1
To primary
Out
Cvc2
22pF
Rvc1
470K
1.210V
+
-
+
-
Ictrl
IL
Vctrl
2.2nF
200mV
Cic1
100nF
Gnd
Ric1
22
R1
+
+
Vsense
Rsense
IL
In the above application schematic, the TSM105 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.
4/9
Load
OUT-
TSM105
PRINCIPLE OF OPERATION AND APPLICATION HINTS
1. Voltage and Current Control
1.1. Voltage Control
The 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 writen 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 Control
The 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-
nuctance 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 3 :
Output voltage versus output current
Vout
Voltage regulation
Current regulation
0
TSM105 Vcc : independent power supply
Secondary current regulation
Iout
TSM105 Vcc : On power output
Primary current regulation
2. Compensation
The voltage-control trans-conductance operation-
al amplifier can be fully compensated. Both its out-
put and the negative input are directly accessible
for external compensation components.
5/9
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