TSM1051 Constant voltage and constant current controller for battery chargers and adaptors Features ■ 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 SO-8 SOT23-6 Description The device is is a highly integrated solution for SMPS applications requiring CV (constant voltage) and CC (constant current) mode. It 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; the current sensing circuit and the other operational amplifier make up the current control loop. The only external components are: – A resistor divider to be connected to the output of the power supply (adaptor, 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 (RC). Housed in one of the smallest package available, it is ideal for space-shrunk applications such as adaptors and battery chargers. Applications Table 1. ■ Adaptors ■ Battery chargers Device summary Order codes Package Packaging TSM1051CLT SOT23-6 Tape and reel TSM1051CD SO-8 Tube TSM1051CDT SO-8 Tape and reel February 2008 Rev 3 1/15 www.st.com 15 Contents TSM1051 Contents 1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.3 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.4 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.5 Operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3 Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1 Internal schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2 Typical application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4 Typical electrical performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.1 Voltage and current control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.1.1 Voltage control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.1.2 Current control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.2 Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.3 Start up and short circuit conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2/15 TSM1051 Description 1 Description 1.1 Pin connection Figure 1. Pin connection (top view) -8 1.2 Pin description Table 2. Pin out Pin n° Name Type Function SOT23 - 6 SO-8 Vctrl 1 1 Analog input Input pin of the voltage control loop Gnd 2 8 Power supply Ground line. 0 V reference for all voltages Out 3 7 Current sink output Output pin. sinking current only Ictrl 4 6 Analog input Input pin of the current control loop Vsense 5 3 Analog input Input pin of the current control loop VCC 6 2 Power supply Positive power supply line Nc 5 Not internally connected Nc 4 Not internally connected. 3/15 Description 1.3 TSM1051 Absolute maximum ratings Table 3. Absolute maximum ratings Symbol VCC 1.4 Input voltage TJ Maximum junction temperature Unit 14 V -0.3 to Vcc V 150 °C Thermal data Symbol RthJA Thermal data Parameter Thermal resistance junction ambient SOT23 - 6 SO-8 Unit 250 130 °C/W Operating conditions Table 5. Symbol VCC TA 4/15 Value DC supply voltage VI Table 4. 1.5 Parameter Recommended operating conditions Parameter DC supply conditions Ambient temperature range Value Unit 2.5 to 12 V 0 to 85 °C TSM1051 2 Electrical characteristics Electrical characteristics TA = 25 °C and VCC = +5 V (unless otherwise specified) Table 6. Electrical characteristics Symbol Parameter Test condition Min Typ Max 1.1 2 Unit Total current consumption ICC Total supply current - not taking the output sinking current into account mA 0 < TA < 85 °C 1.2 Voltage control loop Gmv Transconduction gain (Vctrl). sink current only (1) Vref Voltage control loop reference (2) Iibv Input bias current (Vctrl) 1 3.5 mA/mV 0 < TA < 85 °C 2.5 1.198 1.21 1.222 V 0 < TA < 85 °C 1.186 1.234 50 nA 0 < TA < 85 °C 100 Current control loop Gmi Transconduction Gain (Ictrl). Sink Current Only (3) VSENSE Current control loop reference (4) 1.5 7 IO = 2.5 mA 196 200 0 < TA < 85 °C IO = 2.5 mA 192 mA/mV 204 mV 208 25 Iibi Current out of pin ICTRL at -200 mV µA 0 < TA < 85 °C 50 Output stage VOL Low output voltage at 10 mA sinking current IOS Output short circuit current. output to vcc. sink current only 200 27 mV 50 mA 0 < TA < 85 °C 35 1. If the voltage on VCTRL (the negative input of the amplifier) is higher than the positive amplifier input(Vref = 1.210 V), and it is increased by 1mV, the sinking current at the output OUT will be increased by 3.5 mA. 2. The internal Voltage Reference is set at 1.210 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 trans-conductance operational amplifier. The internal Voltage Reference is fixed by bandgap, and trimmed to 0.5 % accuracy at room temperature. 3. 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. 4. The internal current sense threshold is set to -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 trans-conduction operational amplifier. 5/15 Schematics TSM1051 3 Schematics 3.1 Internal schematic Figure 2. Block diagram Vcc 6 1.210 V + + 3 OUT 1 Vctrl 2 GND - + 200 mV - 3.2 4 5 Ictrl Vsense Typical application circuit Figure 3. Typical adaptor or battery charger application using the device Vcc TSM1051 1.210 V + R1 6 Rled + 3 OUT - 200 mV Cvc1 1 + Rvc1 Vctrl Vout Cic1 2 4 5 Ictrl Vsense Rsense GND Ric1 R2 Ric2 Iout In the above application schematic, the device is used on the secondary side of a flyback adaptor (or battery charger) to provide an accurate control of voltage and current. The above feedback loop is made with an optocoupler. 6/15 TSM1051 4 Typical electrical performance Typical electrical performance Figure 4. Vref vs ambient temperature Figure 5. Vsense vs ambient temp. Figure 6. Vsense pin input bias current Figure 7. vs ambient temperature Ictrl pin input bias current vs ambient temperature Figure 8. Output short circuit current vs Figure 9. ambient temperature Supply current vs ambient temperature 7/15 Application information TSM1051 5 Application information 5.1 Voltage and current control 5.1.1 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. ( V OUT – V REF ) R 1 = R 2 ⋅ --------------------------------------V REF Eq:1 where Vout is the desired output voltage. To avoid the discharge of the load, the voltage divider R1, R2 should be highly resistive. For this type of application, it is suggested a total value of 100 kΩ (or more) for resistors R1 and R2 As an example, with R2 = 33 kΩ, VOUT = 5 V, VREF = 1.210 V, then R1 = 103.4 kΩ Please note that if a low drop diode is inserted between the load and the voltage divider of the voltage control loop in order to avoid current flowing from the load through the voltage divider, the diode voltage drop should be taken into account in the computation of Equation 1 replacing Vout with Vout + Vdrop. 5.1.2 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 Eq:2 Rsense = Vsense / Ilim Eq:2a 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 that the Rsense resistor should be chosen taking into account the maximum dissipation (Plim) through it during full load operation. Plim = Vsense x Ilim. Eq:3 As an example, with Ilim = 1 A, and Vsense = 200 mV, Plim = 200 mW. Therefore, for most adaptor 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 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 3. The resistors of this voltage divider are matched to provide the best precision possible. The current sinking outputs of the two trans-conductance operational amplifiers are 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. (with power supply of the device indipendent from the output voltage) 8/15 TSM1051 Application information Figure 10. Output voltage versus output current Vout Current regulation Voltage regulation (Vcc of the device independent from output voltage) 5.2 Iout Compensation The voltage-control trans-conductance 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 3. It consists of a capacitor Cvc1 = 2.2 nF and a resistor Rcv1 = 470 kΩ in series. The current-control trans-conductance 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 3. It consists of a capacitor Cic1 = 2.2 nF and a resistor Ric1 = 22 kΩ in series. In order to reduce the dissipation of the device (especially with VCC voltage values close to 12 V) and to increase the stability of the application it is suggested to limit the current flowing in the OUT pin of the device adding a resistor in series with the opto-coupler. An example of a suitable RLED value could be 330 Ω in series with the opto-coupler in case VCC = 12 V. 5.3 Start up and short circuit conditions Under start-up or short-circuit conditions the device is not provided with a high enough supply voltage. This is due to the fact that the chip has its power supply line in common with the power supply line of the system. 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). 9/15 Application information TSM1051 This solution allow a costant current regulation till output goes to 0 V. Attention has to be payed to VCC of the device that cannot be higher than Absolute Maximum Rating. Figure 11. Application circuit able to supply the device even with VOUT = 0 Vcc TSM1051 1.210 V Rs + R1 6 Rled + 3 OUT Ds 200 mV Cvc1 1 + 2 4 5 Ictrl Vsense Rsense Iout 10/15 Vctrl Vout Cic1 Cs Rvc1 GND Ric1 Ric2 R2 TSM1051 6 Package mechanical data 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. 11/15 Package mechanical data Table 7. TSM1051 SOT23-6 mechanical data mm. inch Dim. Min Typ Max A 0.9 A1 Typ Max 1.45 0.035 0.057 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 Note: 0.95 0.037 H 2.6 3 0.102 0.118 L 0.1 0.6 0.004 0.024 θ 0 10° 0 10° Dimensions per JEDEC MO178AB Figure 12. Package dimensions 12/15 Min TSM1051 Package mechanical data Table 8. SO-8 mechanical data mm. inch Dim. Min Typ Max Min Typ Max A 1.35 1.75 0.053 0.069 A1 0.1 0.25 0.004 0.010 A2 1.1 1.65 0.043 0.065 B 0.33 0.51 0.013 0.020 C 0.19 0.25 0.007 0.010 D 4.8 5 0.189 0.197 E 3.8 4 0.150 0.157 e 1.27 0.000 0.050 0.000 H 5.8 6.2 0.228 0.244 h 0.25 0.5 0.010 0.020 L 0.4 1.27 0.016 0.050 k ddd 8° (max.) 0.1 0.004 Figure 13. Package dimensions 13/15 Revision history 7 TSM1051 Revision history Table 9. 14/15 Document revision history Date Revision Changes 8-Jan-2002 1 Initial release. 18-Apr-2006 2 New Template, few updates 12-Feb-2008 3 Updated: Section 6: Package mechanical data on page 11 TSM1051 Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale. Purchasers are solely responsible for the choice, selection and use of the ST products and services described herein, and ST assumes no liability whatsoever relating to the choice, selection or use of the ST products and services described herein. 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