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| GS7660 New Product Vishay formerly General Semiconductor Switched-Capacitor Voltage Converter Description SO-8 8 Pin Dip The GS7660 is a monolithic CMOS switched capacitor voltage converter, designed to be an improved direct replacement of the popular ICL7660, MAX1044 and LTC1044. They perform supply voltage conversions from positive to negative for an input voltage range of +1.5V to +6.0V to their negative complements of -1.5V to -6.0V. The input voltage can also be doubled (VOUT = 2VIN), halved (VOUT = VIN/2), or multiplied (VOUT = n.VIN). Contained on the chip are a series Power Supply regulator, Oscillator, control Circuitry and four Power MOS Switches. The oscillator, when unloaded, oscillates at a nominal frequency of 10 kHz, with an Input voltage of 5.0V. This frequency can be lowered by the addition of an external capacitor to the "Osc" terminal or overdriven by an external frequency source. An Oscillator "boost" function is available to increase the oscillator frequency which will optimize performance of certain parameters. The Lv input can be connected to ground to improve low voltage operation (VIN 3V), or left open for input voltages greater than 3V to reduce power dissipation. The GS7660 provides superior performance over earlier designs by combining low output impedance and low quiescent current with high efficiency and by eliminating diode voltage drop losses. The only external components required are two low cost electrolytic capacitors. Features * Low output impedance ( typical 35 at VIN = 5V ) * Low quiescent current ( typical 36A at VIN = 5V) * High power conversion efficiency ( typical 98% ) * Simple and accurate voltage conversion from positive to negative polarities * Improved latch-up protection * No external diodes required Applications * - 5V supply from + 5V logic supply * EIA/TIA - 232E and EIA/TIA - 562 power supplies * Portable telephones * Data acquisition systems * Personal communications equipment * Panel meters * Handheld instruments Typical Application Circuit VIN (1.5V to 6V) 1 2 5 6 GS7660 3 4 7 8 10F C1 + Required for VIN 3V VOUT = --VIN + 10F C2 Negative Voltage Converter Document Number 74819 24-May-02 www.vishay.com 1 GS7660 Vishay formerly General Semiconductor Ordering Information Order Number Pin Configuration GS7660x x Top View Boost 1 Cap+ 2 GND 3 Cap-- 4 8 VIN 7 OSC 6 LV 5 VOUT GS7660IS (Plastic SO-8) Package Outline P: Plastic Dip S: SO-8 Operating Junction Temperature Range I: -40C to +125C Top View Boost 1 8 VIN GS7660IP (8-Pin Plastic Dip) Cap+ 2 7 OSC GND 3 6 LV Cap-- 4 5 VOUT Test Circuit 1 2 10 F + C1 3 4 BOOST CAP+ GS7660 GND CAP- VIN IS 8 IL COSC External Oscillator RL VIN OSC 7 LV VOUT 6 5 VOUT C2 10F + www.vishay.com 2 Document Number 74819 24-May-02 GS7660 Vishay formerly General Semiconductor Maximum Ratings Ratings at 25C ambient temperature unless otherwise specified. Parameter Supply Voltage (VIN to GND) Input Voltage (Pin 1, 6 and 7) LV Input Current Output Short Circuit Duration Operating Junction Temperature Range Storage Temperature Range Continuous Power Dissipation Plastic Dip (Derate 7.9mW/C above 70C) SO-8 (Derate 6mW/C above 70C) TJ TS PD Symbol VIN VIN LV1 Value 6.0 -0.3V VIN (VIN, +0.3V) 20 Continuous -40 to +125 -65 to +150 630 480 C C mW Unit V V A Note: (1) Stresses beyond those listed above may cause permanent damage to the device. Operating at the levels stated above may affect device reliabllity. Electrical Characteristics VIN = 5.0V LVPin = open, Oscillator free running, I load = 0mA, TA = -40C to +125C unless otherwise noted. Parameter Conditions LV = Open Pin 1,7, VIN = 3V Supply Voltage (1) RL = 10K, LV Open RL = 10K, LV Gnd IL = 20mA, FOSC = 10kHz LV = Open Output Resistance IL = 3mA, FOSC = 1kHz VIN = 2V, LV to Gnd Oscillator Frequency Power Efficiency Voltage Conversion Efficiency Oscillator Sink or Source Current Oscillator Impedance COSC = 0pF, LV to Gnd Pin 1 Open TA = 25C TA = 25C TA = 25C Min - - - 3.0 1.5 - - - - VIN = 5.0V VIN = 2.0V - 2.0 96 98 - - - - Typ 36 - 20 - - 35 - - - 5.0 - 98 99.9 - - 1.0 100 Max 70 100 - 6.0 6.0 70 110 250 370 - - - - 3.0 20 - - m k % % A kHz V A Unit Supply Current RL = 5K, FOSC =10kHz, LV = Open LV = Open VOSC = 0V or VIN LV = Open TA = 25C TA = 25C Pin 1 = 0V Pin 1 = VIN VIN = 2.0V VIN = 5.0V Note: (1) The GS7660 can operate with or without an external output diode over the full temperature and voltage range. Eliminating the diode reduces voltage drop losses. Document Number 74819 24-May-02 www.vishay.com 3 GS7660 Vishay formerly General Semiconductor Ratings and Characteristic Curves (TA = 25C unless otherwise noted) Fig. 1 - Supply Current vs. Supply Voltage 100 50 40 Boost = Open 90 Boost = Open LV = Open 80 Fig. 2 - Power Efficiency vs. Load Current (VIN = 5V) LV = Open 30 20 LV = GND 10 0 1 2 3 4 5 6 Power Efficiency (%) Supply Current (A) 70 60 50 0 10 20 30 40 50 60 70 Supply Voltage (V) Load Current (mA) Fig. 3 - Output Voltage vs. Load Current (VIN = 5V) --2.5 --3.0 Boost = Open LV = Open 2 Fig. 4 - Output Voltage vs. Load Current (VIN = 2V) Output Voltage (V) Output Voltage (V) 1 Boost = Open LV = GND --3.5 0 --4.0 --4.5 --1 --5.0 0 10 20 30 40 50 60 70 --2 --40 --20 0 20 40 60 80 100 120 Load Current (mA) Load Current (mA) Fig. 5 - Oscillator Frequency vs. Supply Voltage 35 Fig. 6 - Oscillator Frequency vs. Value of COSC Oscillation Frequency, FOSC (KHz) 30 25 20 15 10 5 0 10 100 1000 10000 Boost = Open Boost = VIN Oscillation Frequency, FOSC (KHz) 60 50 Boost = Vin LV = GND LV = Open 40 30 20 LV = GND 10 5 1 2 3 4 Boost = Open 5 6 LV = Open Supply Voltage, VIN (V) www.vishay.com 4 External Capacitor (Pin 7 to GND), COSC (pF) Document Number 74819 24-May-02 GS7660 Vishay formerly General Semiconductor Pin Description Pin 1 N.C. 2 3 4 5 6 7 8 CAP+ GND CAP- VOUT LV OSC VIN Name BOOST Function Frequency Boost. Connecting BOOST to VIN increases the oscillator frequency by a factor of five. When the oscillator is driven externally, BOOST has no effect and should be left open. No Connection Connection to positive terminal of Charge-Pump Capacitor Ground. For most applications, the positive terminal of the reservoir capacitor is connected to this pin. Connection to negative terminal of Charge-Pump Capacitor Negative Voltage Output. For most applications, the negative terminal of the reservoir capacitor is connected to this pin. Low-Voltage Operation. Connect to ground for supply voltages below 3.5V. Oscillator Control Input. Connecting an external capacitor reduces the oscillator frequency. Power Supply Positive Voltage Input. (1.5V to 6V). VIN is also the substrate connection. Detailed Description The GS7660 is a charge-pump voltage converter. The basic operations is as follows: Switch pairs S1, S2 and S3, S4 (Fig.7) are alternately closed and opened at the rate of the oscillator frequency divided by two. During the first half of the cycle, when S1 and S2 are closed and S3 and S4 are open, bucket capacitor C1 is charged by input voltage. During the second half of the cycle, when the switches assume the opposite state, capacitor C1 is connected in parallel with output capacitor C2 and any voltage differential causes a transfer of charge from C1 to C2. This process will continue until the voltage across C2 equals the -VIN voltage. In normal operation, the output voltage will be less than -VIN, since the switches have internal resistance and C2 is being discharged by the load. S1 VIN C1 S2 S3 S4 C2 VOUT = -(VIN) Fig. 7 - Ideal Voltage Inverter Document Number 74819 24-May-02 www.vishay.com 5 GS7660 Vishay formerly General Semiconductor f VIN VOUT Design Information Low Voltage (LV) Pin Fig. 10 (below) shows a simplified circuit diagram of the GS7660. C1 C2 RLOAD It shows a voltage regulator between the VIN and Gnd, in series with the Oscillator. Grounding the LV pin removes the regulator from this series path and improves low voltage performance down to 1.5V. For supply voltages less than 3.0V, the LV pin should be connected to ground and left open for voltages above 3.0V. The LV pin can be left grounded over the total range of Input Voltages. This will improve low voltage operation and increase oscillator frequency. The disadvantage is increased quiescent current and reduced efficiency at higher voltages. Fig. 8 - Switched Capacitor Model To better understand the theory of operation, a review of the basic switched capacitor building block is helpful (see Fig. 8). Referring to Fig. 8 and looking at one full cycle of operation, the charge being drained by the load is Qavg or IL x T (T being the time period of one full cycle). All the charge (q) flowing into the output is being delivered by the input to C1 during only half the cycle. Under steadystate condition, C1 will charge to the level of the input voltage (VIN) and discharge to the peak level of the output voltage (VOUT). Therefor the voltage change on C1 is VIN - VOUT. VIN pin 8 S1 CAP+ pin 2 S2 Qavg = q = C1(Vin -Vout) IL x T = C1(Vin -Vout) or IL = f x C1(Vin -Vout) f = 1/T IL = 1 (Vin -Vout) and REQUIV = (See fig. 9) 1 f x C1 f x C1 1M OSCILLATOR BOOST pin 1 OSC pin 7 Q /2 Q S3 S4 CAPpin 4 Where f is one-half the oscillator frequency. This resistance is a major component of the output resistance of switched capacitor circuits. With C1 = C2 = 10F and Fosc = 10kHz, this resistance represents 20. Under the same conditions, the typical value in the "Electrical Characteristics" section of the GS7660 is 35. INTERNAL REGULATOR VOUT pin 5 LV pin 6 GND pin 3 Fig. 10 - Functional Diagram REQUIV VIN REQUIV = 1 f x C1 C2 RLOAD VOUT Fig. 9 - Equivalent Impedance www.vishay.com 6 Document Number 74819 24-May-02 GS7660 Vishay formerly General Semiconductor Oscillator Frequency Control For normal operation, the Boost, and Oscillator Pins should be left open. Connecting the Boost pin to the VIN supply will increase oscillator frequency by a factor of 5, resulting in lower Output Impedance, less ripple, smaller required capacitor values and moves the switching noise out of the audio band. Lower oscillator frequency reduces quiescent current. The oscillator frequency can be further controlled by driving the oscillator input from an external frequency source or lowered , by connecting an external capacitor to the oscillator input. VIN (1.5V to 6V) 1N914 IOUT 1 2 8 R1 200 C1 10F + 8 7 6 5 2VIN (3.0V to 12V) 500k + C2 10F 7 GS7660 3 4 6 5 Efficiency, Output Impedance and Output Ripple The power efficiency of a switched capacitor voltage converter is dependent on the internal losses. The total power loss is: 1 8 VIN (1.5V to 9.0V) 8 7 6 5 P outp. P switch P cap. + + P loss = + P conversion Res. Res. Res. P outp. = IL2 f.C1 Res. P switch P cap. 2 + Res. Res. = IL P conversion = f f = f osc/2 + Vd - Required for V+ < 3.0V + + 10F Vd - + VOUT = 2VIN-2VD 10F 2 7 GS7660 3 4 6 5 (8 RSW + 4 Esr C1 + Esr C2) Figs. 11a and 11b - Voltage Doubler [ 1 C1(Vin -Vout )+ 1 C2(V ripple - 2 Vout. V ripple)] 2 2 2 2 2 Voltage Doubling Figure 11 shows two methods of voltage doubling. In Fig. 11a , R1 is added to ensure that doubling is not inhibited by a non-destructive latch-up at start-up. This condition can occur, since the ground pin (pin 3) is raised above the VIN pin ( pin 8) during start-up. f = f osc/2 Vripple V ripple = IL 1 ( 2. C2 .f + 2 Esr C2) f = f osc/2 R1 increases output impedance and in higher current applications where the voltage drop across R1 exceeds a two diode drop, the doubling circuit of Fig 11b is recommended. The voltage doubler of Fig. 11a is more accurate at low load currents since the voltage drop across the diode is not reflected at the output. Document Number 74819 24-May-02 www.vishay.com 7 GS7660 Vishay formerly General Semiconductor Ultra Precision Voltage Divider (VIN) An ultra precision voltage divider is shown below in Fig. 12. To achieve the 0.002% accuracy, the load current has to be kept below 100nA. However with a slight loss in accuracy, the load current can be increased. C1 10F + 1 2 8 8 7 6 5 1 8 7 7 GS7660 3 4 6 5 C1 10F + 2 GS7660 3 4 6 5 VOUT = --(VIN) VIN (3.0V to 12V) 1 2 8 8 7 6 5 1/4 CD4077 7 C2 20F + C1 + 10F GS7660 3 4 6 5 VIN 0.002% 2 Fig. 14 - Paralleling for Lower Output Resistance + C2 10F Required for VIN < 3V IL 100nA Paralleling For Lower Output Impedance Fig. 14 above shows two GS7660s connected in parallel to achieve a lower output resistance. If the output resistance is dominated by 1/ f C1, which is normally the case with the GS7660, increasing C1 offers a greater advantage than the paralleling of circuits. Fig. 12 - Ultra Precision Voltage Divider Battery Splitter Fig. 13 shows a simple solution to obtain complementary + and - supplies from a single power supply. The output voltages are + and - half the supply voltage. Good accuracy requires low load currents. A disadvantage is the requirement of a floating input supply, which in the case of a battery is not an issue. VB + (6V) - C1 10F 1 2 8 8 7 6 5 +VB /2 (3.0V) Required for VB < 6V -VB /2 (-3.0V) - C2 + 10F Output Common 7 + - 3 4 GS7660 6 5 Fig. 13 - Battery Splitter www.vishay.com 8 Document Number 74819 24-May-02 GS7660 Vishay formerly General Semiconductor SO-8 Case Outline 5.00 4.80 8 7 6 5 4.00 3.80 6.20 5.80 1 2 3 4 Dimensions in millimeters 1.27 (typ.) 0.51 0.33 1.75 1.35 0.25 0.10 1.27 0.40 0.25 0.19 8-Pin Dip Case Outline 10.16 9.01 7.12 6.09 Dimensions in millimeters 8.26 7.62 4.96 2.92 0.36 0.20 3.81 2.92 0.381 (min.) 0.56 0.35 10.92 (max.) 2.54 (Typ.) Document Number 74819 24-May-02 www.vishay.com 9 |
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