VOLTAGE AND CURRENT CONTROLLER

Document overview

  • Manufacturer or author: STMICROELECTRONICS
  • PDF pages: 13

Technical content

■ 1.24V SERIES VOLTAGE REFERENCE WITH 10mA OUTPUT CURRENT AND 1% PRECISION (TSM101A) ■ TWO OPERATIONAL AMPLIFIERS WITH ORED OUTPUT AND 1MHZ GAIN BAND- WIDTH PRODUCT ■ BUILT-IN CURRENT GENERATOR WITH ENABLE/DISABLE FUNCTION ■ 4.5 TO 32V SUPPLY VOLTAGE RANGE ■ SO8 AND DIP8 PACKAGES

DESCRIPTION

The TSM101/TSM101A integrated circuit incorpo- rates a high stability series band gap voltage refer- ence, two ORed operational amplifiers and a cur- rent source. This IC compares the DC voltage and the current level at the output of a switching power supply to an internal reference. It provides a feedback through an optocoupler to the PWM controller IC in the primary side. The controlled current generator can be used to modify the level of current limitation by offsetting the information coming from the current sensing resistor.

APPLICATIONS

This circuit is designed to be used in battery chargers with a constant voltage and a limited out- put current. It can be used in every types of application requir- ing a precision voltage regulation and current limi- tation. Other applications include voltage supervisors, over voltage protection... ORDER CODE N = Dual in Line Package (DIP) D = Small Outline Package (SO) - also available in Tape & Reel (DT) PIN CONNECTIONS (top view) Part Number Temperature Range Package ND TSM101C/AC -20°C, +80°C •• TSM101I/AI -40°C, +105°C •• D SO8 (Plastic Micropackage) N DIP8 (Plastic Package) Vref TSM101/A VOLTAGE AND CURRENT CONTROLLER June 2001

ELECTRICAL CHARACTERISTICS

Tamb = 25°C, VCC = 15V (unless otherwise specified) OPERATIONAL AMPLIFIER: TSM101C/I/AC/AI Symbol Parameter Value Unit VCC DC supply Voltage1) 1. All voltages values, except differential voltage are with respect to network ground terminal. 36 V Iout Output Current2) 2. The voltage reference is not protected against permanent short circuit. 20 mA Pd Power Dissipation 200 mW Vin Input Voltage3) 3. The magnitude of input and output voltages must never exceed -0.3V or VCC -1.5V. -0.3, VCC -1.5 V Iout Input Current ±1 mA Tstg Storage Temperature -40 to +125 °C Tj Maximum Junction Temperature 150 °C Tthja Thermal Resistante Junction to Ambiant 130 to 200 °C/W Symbol Parameter Value Unit VCC Supply Voltage 4.5 to 32 V Toper Operating Free Air Temperature Range Tmax to Tmin Symbol Parameter Min. Typ. Max. Unit ICC Total Supply Current VCC = 1.5V 2 mA Vi Input Voltage Range 0 VCC - 1.5V V Vio Input Offset Voltage 25°C T min. ≤ Tamb ≤ Tmax. mV Iib Input Bias Current @ V in =1.2V on pin and Vin =0V on pin 5 25°C Tmin. ≤ Tamb ≤ Tmax. -700 -1000 -300 0 nA Isink Output Sink Current, Vol =2.5V 25°C Tmin. ≤ Tamb ≤ Tmax. 8 mA Avo Large Signal Voltage Gain R L =2kΩ Tmin. ≤ Tamb ≤ Tmax. 15 V/m V SVR Supply Voltage Rejection Ratio Tmin. ≤ Tamb ≤ Tmax. 65 90 dB CMR Common Mode Rejection Ratio Tmin. ≤ Tamb ≤ Tmax. 80 dB GBP Gain Bandwith Product Vcc =15V, F = 100kHz Vin = 10mV, RL = 2kΩ , CL = 100pF

1 MHz

25°C T min. ≤ Tamb ≤ Tmax. µA

Tamb = 25°C, VCC = 15V (unless otherwise specified) VOLTAGE REFERENCE : TSM101 VOLTAGE REFERENCE : TSM101A CURRENT GENERATOR: TSM101, TSM101A Symbol Parameter TSM101C TSM101I Unit Vref Reference Voltage V Kvt Temperature Stability Tmin ≤Tamb ≤ Tmax 30 100 35 120 ppm/°C R eglo Load Regulation 1 < Iout < 10mA 51 5 51 5 mV R egli Line Regulation 5 < Vin < 32V 3.5 10 3.5 10 mV Symbol Parameter TSM101AC TSM101AI Unit Vref Reference Voltage V Kvt Temperature Stability Tmin ≤Tamb ≤ Tmax 30 100 35 120 ppm/°C R eglo Load Regulation 1 < Iout < 10mA 51 5 51 5 mV R egli Line Regulation 5 < Vin < 32V 3.5 10 3.5 10 mV Symbol Parameter TSM101C/AC TSM101I/AI Unit Io Current Source 1.4 1.4 mA Kcgt Temperature Stability Tmin ≤Tamb ≤ Tmax 500 600 ppm/°C C glir Line Regulation Vcsen Voltage at the enable pin to have Io = 1.4mA Tmin ≤Tamb ≤ Tmax 0.6 0.6 V Vcsdis Voltage at the enable pin to have Io = 0mA T min ≤Tamb ≤ Tmax 22 V Icsen Input Current on the Csen pin Tmin ≤Tamb ≤ Tmax 30 30 µA Icsleak Leakage Current Vcs = 2V Tmin ≤Tamb ≤ Tmax 0.5 2 0.5 2 µA

Vref 1 OUTPUT Voltage Reference Output 1.24V, 10mA max. Do not short circuit Vrin 7 INPUT Voltage Regulation Loop input C rin 5 INPUT Current Limitation Loop Input, connected to the sense resisto C rref 3 INPUT Current Limitation Reference Input C sen 2 INPUT Current source enable input. This current source can be used to offset the voltage measurement on the sense resistor and therefore to modify the charge current. The current source enabled when the input voltage on pin 2 is lower than 0.8V. OUTPUT 6 OUTPUT Output pin common to the voltage regulation and current limitation loops. This output can drive the primary side (LED) of an optocoupler. V cc 8 INPUT Power Supply Input (4.5 to 32V DC) GND 4 INPUT Ground

This technical note shows how to use the TSM101 integrated circuit with a switching mode power supply (SMPS) to realize a battery charger. An example of realization of a 12V Nickel-cadmi- um battery charger is given. 1 - TSM101 PRESENTATION The TSM101 integrated circuit incorporates a high stability series band gap voltage reference, two ORed operational amplifiers and a current source (Figure 1) Figure 1 : TSM101 Schematic Diagram This IC compares the DC voltage and the current level at the output of a switching power supply to an internal reference.It provides a feedback through an optocoupler to the PWM controller IC in the primary side. The controlled current generator can be used to modify the level of current limitation by offsetting the information coming from the current sensing resistor. A great majority of low or medium end power sup- plies is voltage regulated by using shunt program- mable voltage references like the TL431 (Figure 2). The galvanic insulation of the control information is done by using an opto-coupler in linear mode with a variable photo current depending on the dif- ference between the actual output voltage and the desired one. A current limitation is used to protect the power supply against short circuits, but lacks precision. This limitation is generally realized by sensing the current of the power transistor, in the primary side of the SMPS. The role of the TSM101 is to make a fine regula- tion of the output current of the SMPS and a pre- cise voltage limitation. The primary current limitation is conserved and acts as a security for a fail-safe operation if a short-circuit occurs at the output of the charger. 2 - PRINCIPLE OF OPERATION The current regulation loop and the voltage limita- tion loop use an internal 1.24V band-gap voltage reference. This voltage reference has a good pre- cision (better than 1.5%) and exhibits a very stable temperature behavior. The current limitation is performed by sensing the voltage across the low ohmic value resistor R5 and comparing it to a fixed value set by the bridge composed by R2 and R3 (Figure 3). When the voltage on R5 is higher than the voltage on R3 the output of the current loop operational amplifier decreases. The optocoupler current in- creases and tends to reduce the output voltage by the way of the PWM controller. The voltage regulation is done by comparing a part of the output voltage (resistor bridge R6, R7 and P1) to the voltage reference (1.24V). If this part is higher than 1.24V, the output of the voltage loop operational amplifier decreases. Vref APPLICATION NOTE A BATTERY CHARGER USING THE TSM101

Figure 2 : SMPS Using a TL431 as Voltage Controller The optocoupler current increases and tends to reduce the output voltage by the way of the PWM controller. By enabling the TSM101 current source (pin 2) it is possible to offset the current sensing by a volt- age equal to : Voff # R4 * Io with I o = 1.4mA This offset lowers the output charge current and this function can be used to charge two types of batteries having different capacities. The current source is enabled by connecting pin 2 to ground 3 - CALCULATION OF THE ELEMENTS The charge current is regulated at 700mA (if the charge control input is left open) or 200mA (if the charge control input is put to ground ), allowing the charge of two different types of batteries. 3.1 - Voltage limitation The end-of- charge voltage is limited at 1.45V/cell, this is the recommended voltage for an ambient temperature at 25oC. A diode is generally inserted at the output of the charger to avoid the discharge of the battery if the charger is not powered. This diode is sometimes directly integrated in the battery pack. The influ- ence of this diode on the charge is negligible if the voltage drop (0.7V) is taken into account during the design of the charger. The voltage at the output of the charger is :

  • V out = and regarding R6 and R7 :
  • R6= P1, which is a part of R6 and R7 is not considered in this equation. The following values are used on the application board :
  • R7 = 12kΩ
  • R6 = 1kΩ
  • P1 = 220Ω , adjust for Voutput = 15.2V with the battery replaced by a 1kΩ resistor
  • R10 = short circuit
  • C3 = 100nF 3.2 - Current regulation R5 is the sense resistor used for current measure- ment. The current regulation is effective when the volt- age drop across R5 is equal to the voltage on pin 5 of the TSM101 (assuming that the internal cur- rent source is disabled). For medium currents (<1A), a voltage drop across R5 of 200mV = Vr5 is a good value, R5 can be re- alized with standard low cost 0.5W resistors in parallel.
  • R5 = , R5 = 0.285Ω (four 1.2Ω resistor in parallel) R2 and R3 can be chosen using the following for- mula :
  • R2 = CHARGE CONTROL If the pin 2 is left open, the charge current is nom- inal at # 700mA. R6 R7+ Vref  R7× Vr5 R3 Vref Vr5– ×

TSM101 integrates in the same 8 pin DIP or SO package

  • one 1.24V precision voltage reference
  • two operationnal amplifiers
  • two diodes which impose a NOR function on the outputs of the operationnal amplifiers
  • one current source which can be activated/ in- hibited thanks to an external pin. An immediate way to take advantage of the high integration and reliability of TSM101 is to use it as a voltage and current controller on power supplies secondary. The application note AN896 describes precisely how to use TSM101 in an SMPS battery charger. The TSM101 Evaluation Board is adaptable to any power supply or battery charger (SMPS or linear) as a voltage and current controller with minimal constraints from the user. HOW TO USE THE TSM101 EVALUATION BOARD ? The generic Electrical Schematic is shown on fig- ure 1. It represents an incomplete SMPS power supply where the primary side is simplified. The “IN+”and “IN-” power inputs of the evalua- tion board should be connected directly to the power lines of the power supply secondary. The “Vcc” input of the evaluation board should be connected to the auxiliary supply line. In the case of an SMPS power supply, the “Reg” output of the evaluation board should be connect- ed to the Optocoupler input to regulate the PWM block in the primary side. In the case of a linear power supply, the “Reg” output should be con- nected to the base of the darlington to regulate the power output. A diode might be needed on the output of the eval- uation board in the case of a battery charger appli- cation to avoid the discharge of the battery when the charger is not connected. COMPONENTS CALCULATIONS The voltage control is given by the choice of the resistor bridge R6/R7 (and the trimmer P1) due to equation 1 :
  • Vref = R6/(R6+R7)xVout eq1 where Vref = 1.24V Figure 1 EVALUATION BOARD -TECHNICAL NOTE

The current control is given by the choice of the voltage drop through the sense resistor R5 (to be linked to the nominal current of the application) and by the value of the sense resistor itself. For medium currents (< 1A), a good value for the voltage drop through R5 can be Vsense = 200mV (dissipation < 200mW). The resistor bridge R2/R3 should be chosen fol- lowing equation 2 :

  • Vsense = R3/(R2+R3)xVref eq2 The total value of the resistor bridge should be in the range of the kW in order to ensure a proper charge for the voltage reference (in the range of the mA). To set the current limit, the sense resistor R5 should be chosen following equation 3 :
  • Ilim = Vsense/R5 eq3 The internal current generator (Isce) can be used to offset the current limitation with a lower value. This current generator is activated by connecting pin 2 to ground. It is inhibited if pin 2 is connected to the positive rail via the pull up resistor R1. The current offset is given by the choice of the re- sistor R4. If Ilim1 is the current limit calculated in the previ- ous paragraph, and Ilim2 is the current limit that is to be set when pin 2 is connected to ground, R4 should be chosen following equation 4 :
  • R4 = (Vsense - Ilim2xR5)/Isce eq4 where Isce = 1.4mA C4 and C5 are bypass capacitors used to smooth- en the regulated outputs. C2 and C3 are capacitors used for high frequency compensation. EXAMPLES OF COMPONENT LISTS Table 1 summerizes a few examples of compo- nent lists to generate quickly 15V/700mA/200mA, 12V/1A/500mA or 8.2V/200mA/100mA voltage and current regulations. Figure 2 Voltage/ Current Control 15V 700mA 200mA 12V 500mA 8.2V 200mA 100mA R1 10k Ω 10kΩ 10kΩ R2 1.2k Ω 1.2kΩ 1.2kΩ R3 220k Ω 220kΩ 220kΩ R4 100 Ω 68Ω 68Ω R5 1.2 Ω x 4 0.8 Ω x 4 1 Ω x 1 R6 1k Ω 1kΩ 1kΩ R7 12k Ω 8.2kΩ 5.6kΩ P1 100 Ω 100Ω 100Ω 2 straps 0 Ω 0Ω 0Ω C2 100nF 100nF 100nF C3 100nF 100nF 100nF C4 10 µF2 2 µF4 . 7 µF C5 100nF 100nF 100nF

8 PINS - PLASTIC DIP

Dim. Millimeters Inches A 3.32 0.131 a1 0.51 0.020 B 1.15 1.65 0.045 0.065 b 0.356 0.55 0.014 0.022 b1 0.204 0.304 0.008 0.012 D 10.92 0.430 E 7.95 9.75 0.313 0.384 e 2.54 0.100 e3 7.62 0.300 e4 7.62 0.300 F 6.6 0260 i 5.08 0.200 L 3.18 3.81 0.125 0.150 Z 1.52 0.060

8 PINS - PLASTIC MICROPACKAGE (SO)

Dim. Millimeters Inches A 1.75 0.069 a1 0.1 0.25 0.004 0.010 a2 1.65 0.065 a3 0.65 0.85 0.026 0.033 b 0.35 0.48 0.014 0.019 b1 0.19 0.25 0.007 0.010 C 0.25 0.5 0.010 0.020 c1 45° (typ.) D 4.8 5.0 0.189 0.197 E 5.8 6.2 0.228 0.244 e 1.27 0.050 e3 3.81 0.150 F 3.8 4.0 0.150 0.157 L 0.4 1.27 0.016 0.050 M 0.6 0.024 S 8° (max.) b A s L C E D M 8 5 1 4 F Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. © The ST logo is a registered trademark of STMicroelectronics © 2001 STMicroelectronics - Printed in Italy - All Rights Reserved STMicroelectronics GROUP OF COMPANIES Australia - Brazil - China - Finland - France - Germany - Hong Kong - India - Italy - Japan - Malaysia - Malta - Morocco Singapore - Spain - Sweden - Switzerland - United Kingdom © http://www.st.com