February 2008 Rev 2 1/15
15
TSM1052
Constant voltage and constant current controller
for battery chargers and adapters
Features
■Secondary-side constant voltage and constant
current control
■Very low voltage operation
■Very low quiescent consumption
■High-accuracy internal reference
■Low external component count
■Wired-or open-drain output stage
■Easy frequency compensation
■SOT23-6 micro package
Applications
■Battery chargers
■AC DC adapters
Description
The TSM1052 is a highly integrated solution for
SMPS applications requiring a dual control loop to
perform CV (constant voltage) and CC (constant
current) regulation.
The TSM1052 integrates a voltage reference, two
op amps (with OR-ed open-drain outputs), and a
low-side current sensing circuit.
The voltage reference, along with one op amp, is
the core of the voltage control loop; the current
sensing circuit and the other op amp make up the
current control loop.
The external components needed to complete the
two control loops are:
■A resistor divider that senses the output of the
power supply (adapter, battery charger) and
fixes the voltage regulation set point at the
specified value;
■A sense resistor that feeds the current sensing
circuit with a voltage proportional to the dc
output current; this resistor determines the
current regulation set point and must be
adequately rated in terms of power dissipation;
■Frequency compensation components
(RC networks) for both loops.
The TSM1052, housed in one of the smallest
package available, is ideal for space-shrunk
applications such as adapters and chargers.
SOT23-6
www.st.com
Table 1. Device summary
Part number Package Packaging
TSM1052 SOT23-6 Tape and reel
Contents TSM1052
2/15
Contents
1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Internal schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.5 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3 Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1 Typical application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2 Voltage and current control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2.1 Voltage control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2.2 Current control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.3 Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.4 Start up and short circuit conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5 Mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
TSM1052 Description
3/15
1 Description
1.1 Pin connection
Figure 1. Pin Connection (top view)
1.2 Pin description
Vcc
Vsense
Ictrl
Vctrl
OUT
GND
1
2
3
6
5
4
Vcc
Vsense
Ictrl
Vcc
Vsense
Ictrl
Vctrl
OUT
GND
Vctrl
OUT
GND
1
2
3
6
5
4
1
2
3
6
5
4
1
2
3
6
5
4
Vcc
Vsense
Ictrl
Vctrl
OUT
GND
1
2
3
6
5
4
Vcc
Vsense
Ictrl
Vcc
Vsense
Ictrl
Vctrl
OUT
GND
Vctrl
OUT
GND
1
2
3
6
5
4
1
2
3
6
5
4
1
2
3
6
5
4
Table 2. Pin description
N. Name Function
1V
ctrl
Inverting input of the voltage loop op amp. The pin will be tied to the mid-point
of a resistor divider that senses the output voltage.
2GND
Ground. Return of the bias current of the device. 0 V reference for all
voltages. The pin should be tied as close to the ground output terminal of the
converter as possible to minimize load current effect on the voltage regulation
set point.
3OUT
Common open-drain output of the two internal op amps. The pin, able to sink
current only, will be connected to the branch of the optocoupler’s photodiode
to transmit the error signal to the primary side.
4I
ctrl
Non-inverting input of the current loop op amp. It will be tied directly to the hot
(negative) end of the current sense resistor
5V
sense
Inverting input of the current loop op amp. The pin will be tied to the cold end
of the current sense resistor through a decoupling resistor.
6Vcc
Supply Voltage of the device. A small bypass capacitor (0.1 µF typ.) to GND,
located as close to IC’s pins as possible, might be useful to get a clean
supply voltage.
Description TSM1052
4/15
1.3 Internal schematic
Figure 2. Internal schematic
1.4 Absolute maximum ratings
1.5 Thermal data
Vctrl
GND
VsenseIctrl
OUT
Vcc
1.238 V
200 mV
+
-
+
-
+
1
2
3
54
6
Vctrl
GND
VsenseIctrl
OUT
Vcc
1.238 V
200 mV
+
-
+
-
+
1
2
3
54
6
1.21 V
Vctrl
GND
VsenseIctrl
OUT
Vcc
1.238 V
200 mV
+
-
+
-
+
1
2
3
54
6
Vctrl
GND
VsenseIctrl
OUT
Vcc
1.238 V
200 mV
+
-
+
-
+
1
2
3
54
6
1.21 V
Table 3. Absolute maximum ratings
Symbol Pin Parameter Value Unit
VCC 6 DC supply voltage -0.3 to 20 V
VOUT 3 Open-drain voltage -0.3 to VCC V
IOUT 3 Max sink current 100 mA
V 1, 4, 5 Analog inputs -0.3 to 3.3 V
Table 4. Thermal data
Symbol Parameter Value Unit
RthJA Thermal resistance, junction-to-ambient 250 °C/W
TOP Junction temperature operating range -10 to 85
°CTjmax Maximum junction temperature 150
TSTG Storage temperature -55 to 150
TSM1052 Electrical characteristics
5/15
2 Electrical characteristics
TJ = 25 °C and VCC = 5 V, unless otherwise specified
Table 5. Electrical characteristics
Symbol Parameter Test conditions Min Typ Max Unit
Device supply
VCC Voltage operating range 1.7 18 V
ICC
Quiescent current
(Ictrl = Vsense = Vctr = 0,
OUT = open)
150
µA
(1)
1. Specification referred to -10 °C < TA < 85 °C
300
Voltage control loop op amp
Gmv
Transconductance
(sink current only) (2)
2. If the voltage on Vctrl (the negative input of the amplifier) is higher than the positive amplifier input
(Vref = 1.21 V), and it is increased by 1mV, the sinking current at the output OUT will be increased by
3.5 mA.
13.5 S
(1) 2.5
Vref Voltage reference (3)
3. The internal Voltage Reference is set at 1.21 V (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 transconductance operational amplifier. The internal Voltage Reference is fixed by
bandgap, and trimmed to 0.5% accuracy at room temperature.
1.198 1.21 1.222 V
(1) 1.186 1.234
Ibias Inverting input bias current 50 nA
(1) 100
Current control loop
Gmi
Transconductance
(sink current only) (4)
4. When the positive input at Ictrl is lower than -200 mV, and the voltage is decreased by 1mV, the sinking
current at the output Out will be increased by 7 mA.
1.5 7 S
(1)
Vsense Current loop reference (5)
@ I(Iout) = 1 mA
5. The internal current sense threshold is set at -200 mV. 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 transconductance operational amplifier.
196 200 204 mV
(1) 192 208
Ibias Non-inverting input source current @
V(Ictrl) = -200 mV
20 µA
(1) 40
Output stage
VOUTlow Low output level @ 2 mA sink current 100 mV
(1) 200
Typical characteristics TSM1052
6/15
3 Typical characteristics
Figure 3. Vref vs ambient temperature Figure 4. VSENSE vs ambient temperature
Figure 5. VSENSE pin input bias current vs
ambient temperature
Figure 6. ICTRL pin input bias current vs
ambient temperature
Figure 7. Transconductances (sink current
only) of voltage control loop op amp
vs ambient temperature
Figure 8. Transconductance (sink current
only) of current control loop op amp
vs ambient temperature
1.190
1.200
1.210
1.220
1.230
-20 0 20 40 60 80 100
Temp ( °C )
Vref (V)
Vcc=18V Vcc=5V Vcc=1.7V
192
194
196
198
200
202
204
206
208
-20 0 20 40 60 80 100
Temp ( °C )
Vsense (mV)
Vcc=18V Vcc=5V Vcc=1.7V
0
10
20
30
40
50
-20 0 20 40 60 80 100
Temp ( °C )
Iibv(nA)
Vcc=18V Vcc=5V Vcc=1.7V
10
11
12
13
14
15
-20 0 20 40 60 80 100
Temp ( °C )
Iibi(uA)
Vcc=18V Vcc=5V Vcc=1.7V
0
2
4
6
8
10
12
14
16
18
-20 0 20 40 60 80 100
Temp ( °C )
Gmv(mA/mV)
Vcc=18V Vcc=5V Vcc=1.7V
0
5
10
15
20
-20 0 20 40 60 80 100
Temp ( °C )
Gmi(mA/mV)
Vcc=18V Vcc=5V Vcc=1.7V
TSM1052 Typical characteristics
7/15
Figure 9. Low output level of voltage control
loop op amp vs ambient
temperature (2 mA sink current)
Figure 10. Low output level of current control
loop op amp vs ambient
temperature (2 mA sink current)
Figure 11. Output short circuit current of
voltage control loop op amp vs
ambient temperature
Figure 12. Output short circuit current of
current control loop op amp vs
ambient temperature
Figure 13. Supply current vs ambient
temperature
Figure 14. Low output level vs sink current
0
20
40
60
80
100
120
-20 0 20 40 60 80 100
Temp ( °C )
Volv(mV)
Vcc=18V Vcc=5V Vcc=1.7V
0
20
40
60
80
100
120
140
-20 0 20 40 60 80 100
Temp ( °C )
Volc(mV)
Vcc=18V Vcc=5V Vcc=1.7V
0
10
20
30
40
50
60
70
-20 0 20 40 60 80 100
Temp ( °C )
Iosv(mA)
Vcc=18V Vcc=5V Vcc=1.7V
0
10
20
30
40
50
60
70
80
-20 0 20 40 60 80 100
Temp ( °C )
Iosc(mA)
Vcc=18V Vcc=5V Vcc=1.7V
0.000
0.050
0.100
0.150
0.200
0.250
0.300
0.350
-20 0 20 40 60 80 100
Temp ( °C )
Icc(uA)
Vcc=18V Vcc=5V Vcc=1.7V
0
0.5
1
1.5
2
2.5
1 6 11 16 21 26 31
Isink (mA)
Vol (V)
Application information TSM1052
8/15
4 Application information
4.1 Typical application schematic
Figure 15. Typical adapter or battery charger application using the device
In the above application schematic, the device 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.
4.2 Voltage and current control
4.2.1 Voltage control
The voltage loop is controlled via a first transconductance operational amplifier, the voltage
divider R1, R2, and the optocoupler which is directly connected to the output. Its possible to
choose the values of R1 and R2 resistors using Equation 1:
Equation 1
where Vout is the desired output voltage.
As an example, with R1 = 100 kΩ and R2 = 27 kΩ, VOUT = 5.7 V
Rsense
Iout
Vout
Vctrl
GND
VsenseIctrl
OUT
Vcc
1.210 V
200 mV
+
-
+
-
+
1
2
3
54
6
R1
R2
TSM1052
Ric2
Ric1
Cic1
Cvc1 Rvc1
Rled
Rsense
Iout
Vout
Vctrl
GND
VsenseIctrl
OUT
Vcc
1.210 V
200 mV
+
-
+
-
+
1
2
3
54
6
R1
R2
TSM1052
Ric2
Ric1
Cic1
Cvc1 Rvc1
Rled
a)
b)
2
21
refout R
)RR(
VV +
⋅=
ref
refout
21 V
)VV(
RR −
⋅=
TSM1052 Application information
9/15
4.2.2 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:
Equation 2
where Ilim is the desired limited current, and VSENSE is the threshold voltage for the current
control loop.
As an example, with Ilim = 1 A, VSENSE = 200 mV, then RSENSE = 200 mΩ.
Note: The Rsense resistor should be chosen taking into account the maximum dissipation (Plim)
through it during full load operation.
Equation 3
As an example, with Ilim = 1 A, and Vsense = 200 mV, Plim = 200 mW.
Therefore, for most adapter and battery charger applications, a quarter-watt, or half-watt
resistor is sufficient. VSENSE threshold is made internally by a voltage divider tied to the Vref
voltage reference. Its middle point 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 Figure 15 on page 8. The resistors of this voltage divider are matched
to provide the best possible accuracy. The current sinking outputs of the two
transconductance operational amplifiers are common (to the output of the IC). This makes
an ORing function which ensures either the voltage control or the current control, driving the
optocoupler's photodiode to transmit the feedback to the primary side.
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 diagram.
(with the power supply of the device indipendent of the output voltage)
a)
b)
lim
sense
sense I
V
R=
senselimsense VIR
=
⋅
limsenselim IVP
⋅
=
Application information TSM1052
10/15
Figure 16. Output voltage versus output current
4.3 Compensation
The voltage control transconductance operational 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 Figure 15. It consists of a
capacitor CVC1 = 2.2 nF and a resistor RCV1 = 470 kΩ in series.
The current-control transconductance operational amplifier can be fully compensated. Both
its output and negative input are directly accessible for external compensation components.
An example of a suitable compensation network is shown in Figure 15. It consists of a
capacitor CIC1 = 2.2 nF and a resistor RIC1 = 22 kΩ in series. In order to increase the
stability of the application it is suggested to add a resistor in series with the optocoupler. An
example of a suitable RLED value could be 330 Ω in series with the optocoupler.
4.4 Start up and short circuit conditions
Under start-up or short-circuit conditions if the device is supplied from SMPS output and the
output voltage is lower than Vcc minimum the current regulation is not guaranteed.
Therefore, the current limitation can only be ensured by the primary PWM module, which
should be chosen accordingly.
If the primary current limitation is considered not to be precise enough for the application,
then a sufficient supply for the device has to be ensured under any condition. It would then
be necessary to add some circuitry to supply the chip with a separate power line. This can
be achieved in numerous ways, including an additional winding on the transformer.
The following schematic shows how to realize a low-cost power supply for the device (with
no additional windings).
Vout
Iout
Voltage regulation
Current regulation
( Vcc of the device independent of output voltage)
Vout
Iout
Voltage regulation
Current regulation
( Vcc of the device independent
TSM1052 Application information
11/15
Figure 17. Application circuit able to supply the device even with VOUT = 0
Rsense
Iout
Vout
R1
R2
Vctrl
GND
VsenseIctrl
OUT
Vcc
1.210 V
200 mV
+
-
+
-
+
1
2
3
54
6
TSM1052
Ric2
Ric1
Cic1
Cvc1 Rvc1
Rled
Rs
Ds
Cs
Rsense
Iout
Vout
R1
R2
Vctrl
GND
VsenseIctrl
OUT
Vcc
1.210 V
200 mV
+
-
+
-
+
1
2
3
54
6
TSM1052
Vctrl
GND
VsenseIctrl
OUT
Vcc
1.210 V
200 mV
+
-
+
-
+
1
2
3
54
6
TSM1052
Ric2
Ric1
Cic1
Cvc1 Rvc1
Rled
Rs
Ds
Cs
Package mechanical data TSM1052
12/15
5 Package mechanical data
In order to meet environmental requirements, ST offers these devices in ECOPACK®
packages. These packages have a Lead-free second level interconnect. The category of
second Level Interconnect is marked on the package and on the inner box label, in
compliance with JEDEC Standard JESD97. The maximum ratings related to soldering
conditions are also marked on the inner box label. ECOPACK is an ST trademark.
ECOPACK specifications are available at: www.st.com.
TSM1052 Package mechanical data
13/15
Note: Dimensions per JEDEC MO178AB
Figure 18. Package dimensions
Table 6. SOT23-6 mechanical data
Dim.
mm. inch
Min Typ Max Min Typ Max
A 0.9 1.45 0.035 0.057
A1 0 0.1 0 0.0039
A2 0.9 1.3 0.035 0.0512
b 0.35 0.5 0.014 0.02
c 0.09 0.2 0.004 0.008
D 2.8 3.05 0.11 0.120
E 1.5 1.75 0.059 0.0689
e 0.95 0.037
H 2.6 3 0.102 0.118
L 0.1 0.6 0.004 0.024
θ0 10° 0 10°
TSM1052
15/15
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