TSM1052

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: ■ 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; ■ The TSM1052 integrates a voltage reference, two op amps (with OR-ed open-drain outputs), and a low-side current sensing circuit. 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; ■ 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. 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. 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. Table 1. Device summary Part number Package Packaging TSM1052 SOT23-6 Tape and reel February 2008 Rev 2 1/15 www.st.com 15 Contents TSM1052 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 2/15 TSM1052 Description 1 Description 1.1 Pin connection Figure 1. 1.2 Pin Connection (top view) Vctrl 1 6 Vcc GND 2 5 Vsense OUT 3 4 Ictrl Pin description Table 2. Pin description N. Name Function 1 Vctrl 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. 2 GND 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. 3 OUT 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. 4 Ictrl Non-inverting input of the current loop op amp. It will be tied directly to the hot (negative) end of the current sense resistor 5 Vsense 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. 6 Vcc 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. 3/15 Description 1.3 TSM1052 Internal schematic Figure 2. Internal schematic Vcc 6 1.21 V V 1.238 + + 3 OUT 1 Vctrl 2 GND - + 200 mV - 1.4 5 Ictrl Vsense Absolute maximum ratings Table 3. 1.5 4 Absolute maximum ratings Symbol Pin VCC 6 VOUT Parameter Value Unit DC supply voltage -0.3 to 20 V 3 Open-drain voltage -0.3 to VCC V IOUT 3 Max sink current 100 mA V 1, 4, 5 -0.3 to 3.3 V Value Unit 250 °C/W Analog inputs Thermal data Table 4. Thermal data Symbol 4/15 Parameter RthJA Thermal resistance, junction-to-ambient TOP Junction temperature operating range Tjmax Maximum junction temperature TSTG Storage temperature -10 to 85 150 -55 to 150 °C TSM1052 2 Electrical characteristics Electrical characteristics TJ = 25 °C and VCC = 5 V, unless otherwise specified Table 5. Electrical characteristics Symbol Parameter Test conditions Min Typ Max Unit 18 V Device supply VCC Voltage operating range ICC Quiescent current (Ictrl = Vsense = Vctr = 0, OUT = open) 1.7 150 µA (1) 300 Voltage control loop op amp Gmv Transconductance (sink current only) (2) Vref Voltage reference (3) 1 S (1) 2.5 1.198 (1) 3.5 1.21 1.222 V 1.186 1.234 50 Ibias Inverting input bias current nA (1) 100 Current control loop Gmi Vsense Ibias 1.5 Transconductance (sink current only) (4) (1) Current loop reference (5) @ I(Iout) = 1 mA (1) Non-inverting input source current @ V(Ictrl) = -200 mV (1) 7 S 196 200 204 mV 192 208 20 µA 40 Output stage 100 VOUTlow Low output level @ 2 mA sink current (1) mV 200 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. 5/15 Typical characteristics TSM1052 3 Typical characteristics Figure 3. Vref vs ambient temperature Vcc=18V Vcc=5V Figure 4. Vcc=18V Vcc=1.7V 1.230 Vsense (mV) Vref (V) 1.220 1.210 1.200 1.190 -20 0 20 40 VSENSE vs ambient temperature 60 80 -20 100 0 20 Vcc=18V 50 15 40 14 30 13 20 80 100 Vcc=5V Vcc=1.7V 12 11 0 10 -20 0 20 40 60 80 100 -20 0 20 Temp ( °C ) Figure 7. 40 60 80 100 Temp ( °C ) Transconductances (sink current Figure 8. only) of voltage control loop op amp vs ambient temperature Vcc=18V Vcc=5V Transconductance (sink current only) of current control loop op amp vs ambient temperature Vcc=18V Vcc=1.7V Vcc=5V Vcc=1.7V 20 18 16 14 12 10 8 6 4 2 0 Gmi(mA/mV) Gmv(mA/mV) 60 ICTRL pin input bias current vs ambient temperature Vcc=1.7V Iibi(uA) Iibv(nA) Vcc=5V Figure 6. 10 15 10 5 0 -20 0 20 40 Temp ( °C ) 6/15 40 Temp ( °C ) VSENSE pin input bias current vs ambient temperature Vcc=18V Vcc=1.7V 208 206 204 202 200 198 196 194 192 Temp ( °C ) Figure 5. Vcc=5V 60 80 100 -20 0 20 40 Temp ( °C ) 60 80 100 TSM1052 Figure 9. Typical characteristics Low output level of voltage control loop op amp vs ambient temperature (2 mA sink current) Vcc=18V Vcc=5V Figure 10. Low output level of current control loop op amp vs ambient temperature (2 mA sink current) Vcc=1.7V Vcc=18V 120 80 Volc(mV) Volv(mV) 100 60 40 20 0 -20 0 20 40 60 80 -20 100 0 20 Iosv(mA) Vcc=5V Vcc=1.7V Vcc=18V Iosc(mA) 20 40 60 80 100 100 Vcc=5V Vcc=1.7V -20 0 20 40 60 80 100 Temp ( °C ) Figure 13. Supply current vs ambient temperature Vcc=5V Figure 14. Low output level vs sink current Vcc=1.7V 2.5 0.350 0.300 0.250 0.200 0.150 0.100 0.050 0.000 2 Vol (V) Icc(uA) 80 80 70 60 50 40 30 20 10 0 Temp ( °C ) Vcc=18V 60 Figure 12. Output short circuit current of current control loop op amp vs ambient temperature 70 60 50 40 30 20 10 0 0 40 Temp ( °C ) Figure 11. Output short circuit current of voltage control loop op amp vs ambient temperature -20 Vcc=1.7V 140 120 100 80 60 40 20 0 Temp ( °C ) Vcc=18V Vcc=5V 1.5 1 0.5 0 -20 0 20 40 Temp ( °C ) 60 80 100 1 6 11 16 21 26 31 Isink (mA) 7/15 Application information TSM1052 4 Application information 4.1 Typical application schematic Figure 15. Typical adapter or battery charger application using the device Vcc TSM1052 1.210 V + R1 6 Rled + 3 OUT - 200 mV Cvc1 1 + Rvc1 Vctrl Vout Cic1 2 4 5 Ictrl Vsense GND Ric1 R2 Ric2 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 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 a) Vout = Vref ⋅ b) R1 = R2 ⋅ (R1 + R 2 ) R2 (Vout − Vref ) Vref where Vout is the desired output voltage. As an example, with R1 = 100 kΩ and R2 = 27 kΩ, VOUT = 5.7 V 8/15 TSM1052 4.2.2 Application information 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) R sense ⋅ Ilim = Vsense b) 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 mΩ. 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 TSM1052 Figure 16. Output voltage versus output current Vout Voltage regulation Current regulation (Vcc of the device independent of output voltage) 4.3 Iout 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). 10/15 TSM1052 Application information Figure 17. Application circuit able to supply the device even with VOUT = 0 Vcc TSM1052 1.210 V Rs + R1 6 Rled + 3 OUT Ds 200 mV Cvc1 1 + Vctrl Vout Cic1 2 Cs Rvc1 4 5 Ictrl Vsense Rsense GND Ric1 R2 Ric2 Iout 11/15 Package mechanical data 5 TSM1052 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. 12/15 TSM1052 Package mechanical data Table 6. 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 Min 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 18. Package dimensions 13/15 Revision history 6 TSM1052 Revision history Table 7. 14/15 Document revision history Date Revision Changes 20-Feb-2007 1 Initial release. 07-Feb-2008 2 Updated: Section 5 on page 12 TSM1052 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. 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