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
SOT23-6
Applications
Battery chargers AC DC adapters
The external components needed to complete the two control loops are:
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.
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.
Table 1.
Device summary
Part number TSM1052 Package SOT23-6 Packaging Tape and reel
February 2008
Rev 2
1/15
www.st.com 15
Contents
TSM1052
Contents
1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 1.2 1.3 1.4 1.5 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Internal schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 3 4
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1 4.2 Typical application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Voltage and current control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2.1 4.2.2 Voltage control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Current control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.3 4.4
Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Star t up and short circuit conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5 6
Mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
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TSM1052
Description
1
1.1
Description
Pin connection
Figure 1. Pin Connection (top view)
Vctrl GND OUT
1 2 3
6 5 4
Vcc Vsense Ictrl
1.2
Pin description
Table 2.
N. 1
Pin description
Name Vctrl Function Inver ting 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. 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. 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. Non-inver ting input of the current loop op amp. It will be tied directly to the hot (negative) end of the current sense resistor Inver ting 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. Supply Voltage of the device. A small bypass capacitor (0.1 F typ.) to GND, located as close to IC's pins as possible, might be useful to get a clean supply voltage.
2
GND
3
OUT
4 5
Ictrl Vsense
6
Vcc
3/15
Description
TSM1052
1.3
Internal schematic
Figure 2. Internal schematic
Vcc
1..23V V 121 8
6
+
+ -
3
OUT
200 mV
+ -
1 2 5
Vctrl GND
4 Ictrl
Vsense
1.4
Absolute maximum ratings
Table 3.
Symbol VCC VOUT IOUT V
Absolute maximum ratings
Pin 6 3 3 1, 4, 5 Parameter DC supply voltage Open-drain voltage Max sink current Analog inputs Value -0.3 to 20 -0.3 to VCC 100 -0.3 to 3.3 Unit V V mA V
1.5
Thermal data
Table 4.
Symbol RthJA TOP Tjmax TSTG
Thermal data
Parameter Thermal resistance, junction-to-ambient Junction temperature operating range Maximum junction temperature Storage temperature Value 250 -10 to 85 150 -55 to 150 C Unit C/W
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TSM1052
Electrical characteristics
2
Electrical characteristics
TJ = 25 C and VCC = 5 V, unless otherwise specified Table 5.
Symbol Device supply VCC ICC Voltage operating range Quiescent current (Ictrl = Vsense = Vctr = 0, OUT = open) 1.7 150
(1)
Electrical characteristics
Parameter Test conditions Min Typ Max Unit
18
V A
300
Voltage control loop op amp G mv Transconductance (sink current only) (2) Voltage reference (3) 1
(1)
3.5 S 2.5
1.198
(1)
1.21
1.222 V 1.234
Vref
1.186 50
Ibias
Inver ting input bias current
(1)
nA 100
Current control loop Gmi Transconductance (sink current only) (4) Current loop reference (5) @ I(Iout) = 1 mA Non-inver ting input source current @ V(Ictrl) = -200 mV 1.5
(1)
7 S
196
(1)
200
204 mV 208
Vsense
192 20
Ibias
(1)
A 40
Output stage 100 VOUTlow Low output level @ 2 mA sink current
1. Specification referred to -10 C < TA < 85 C 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. 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. 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. 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.
(1)
mV 200
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Typical characteristics
TSM1052
3
Figure 3.
Typical characteristics
Vref vs ambient temperature
Vcc=18V 1.230 Vcc=5V Vcc=1.7V
Figure 4.
VSENSE vs ambient temperature
Vcc=18V Vcc=5V Vcc=1.7V
1.210 1.200 1.190 -20 0 20 40 Temp ( C ) 60 80 100
Vsense (mV)
1.220 Vref (V)
208 206 204 202 200 198 196 194 192 -20 0 20 40 Temp ( C ) 60 80 100
Figure 5.
VSENSE pin input bias current vs ambient temperature
Vcc=18V Vcc=5V Vcc=1.7V
Figure 6.
ICTRL pin input bias current vs ambient temperature
Vcc=18V Vcc=5V Vcc=1.7V
50 40 Iibv(nA) Iibi(uA) -20 0 20 40 Temp ( C ) 60 80 100 30 20 10 0
15 14 13 12 11 10 -20 0 20 40 Temp ( C ) 60 80 100
Figure 7.
Transconductances (sink current Figure 8. only) of voltage control loop op amp vs ambient temperature
Vcc=18V Vcc=5V Vcc=1.7V 20 Gmi(mA/mV) 15 10 5 0
Transconductance (sink current only) of current control loop op amp vs ambient temperature
Vcc=18V Vcc=5V Vcc=1.7V
18 16 14 12 10 8 6 4 2 0 -20 0 20 40 Temp ( C ) 60 80 100
Gmv(mA/mV)
-20
0
20
40 Temp ( C )
60
80
100
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TSM1052 Figure 9. Low output level of voltage control loop op amp vs ambient temperature (2 mA sink current)
Vcc=18V 120 100 Volv(mV) 60 40 20 0 -20 0 20 40 Temp ( C ) 60 80 100 Volc(mV) 80 Vcc=5V Vcc=1.7V 140 120 100 80 60 40 20 0 -20 0 20
Typical characteristics Figure 10. Low output level of current control loop op amp vs ambient temperature (2 mA sink current)
Vcc=18V Vcc=5V Vcc=1.7V
40 Temp ( C )
60
80
100
Figure 11. Output short circuit current of voltage control loop op amp vs ambient temperature
Vcc=18V 70 60 50 40 30 20 10 0 -20 0 20 40 Temp ( C ) 60 80 100 Vcc=5V Vcc=1.7V
Figure 12. Output short circuit current of current control loop op amp vs ambient temperature
Vcc=18V 80 70 60 50 40 30 20 10 0 -20 0 20 40 Temp ( C ) 60 80 100 Vcc=5V Vcc=1.7V
Iosv(mA)
Figure 13. Supply current vs ambient temperature
Vcc=18V 0.350 0.300 0.250 0.200 0.150 0.100 0.050 0.000 -20 0 20 40 Temp ( C ) 60 80 100 Vcc=5V Vcc=1.7V
Figure 14. Low output level vs sink current
Iosc(mA)
Vol (V)
2.5 2 1.5 1 0.5 0 1 6 11 16 21 26 31 Isink (mA)
Icc(uA)
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Application information
TSM1052
4
4.1
Application information
Typical application schematic
Figure 15. Typical adapter or battery charger application using the device
TSM1052
1.210 V +
Vcc 6 Rled 3 OUT Cvc1 1 2 5 Vsense Ric2 Vctrl Cic1 GND Ric1
R1
+ -
Rvc1 Vout
200 mV
+ -
4 Ictrl
R2
Rsense Rsense Iout
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
4.2.1
Voltage and current control
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 a) b)
Vout = Vref R1 = R2
(R1 + R 2 ) R2
(Vout - Vref ) Vref
where Vout is the desired output voltage. As an example, with R1 = 100 k and R2 = 27 k, VOUT = 5.7 V
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TSM1052
Application information
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
a) b)
R sense Ilim = Vsense R sense = Vsense Ilim
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 m.
Note: The Rsense resistor should be chosen taking into account the maximum dissipation (Plim) through it during full load operation. Equation 3
Plim = Vsense Ilim 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)
9/15
Application information Figure 16. Output voltage versus output current
TSM1052
V ou t
V oltag e regulation C urr en t regulation
(Vcc of the device independent of output voltage)
Iout
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 k 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 k 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 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).
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TSM1052
Application information Figure 17. Application circuit able to supply the device even with VOUT = 0
TSM1052
1.210 V Rs +
Vcc 6 Rled 3 OUT Cvc1 1 2 5 Vsense Ric2 Vctrl Cic1 GND Ric1
R1
+ -
Rvc1 Vout
Ds
200 mV
+ -
Cs
4 Ictrl
R2
Rsense Rsense I out
11/15
Package mechanical data
TSM1052
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.
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TSM1052
Package mechanical data
Table 6.
Dim.
SOT23-6 mechanical data
mm. Min Typ 0.9 0 0.9 0.35 0.09 2.8 1.5 0.95 2.6 0.1 0 3 0.6 10 Max 1.45 0.1 1.3 0.5 0.2 3.05 1.75 0.037 0.102 0.004 0 0.118 0.024 10 Min inch Typ 0.035 0 0.035 0.014 0.004 0.11 0.059 Max 0.057 0.0039 0.0512 0.02 0.008 0.120 0.0689
A A1 A2 b c D E e H L
Note:
Dimensions per JEDEC MO178AB Figure 18. Package dimensions
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Revision history
TSM1052
6
Revision history
Table 7.
Date 20-Feb-2007 07-Feb-2008
Document revision history
Revision 1 2 Initial release. Updated: Section 5 on page 12 Changes
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TSM1052
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