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| TK11830 POSITIVE-TO-NEGATIVE DC-DC CONVERTER FEATURES s s s s s s Positive-to-Negative Converter Adjustable Output Voltage On/Off Control Thermal Protection Sensor Broad Operating Voltage Range Miniature Package (SOT-23L) APPLICATIONS s s s s s s s Pagers Cassette Recorders Cordless Telephones Portable Instrumentation Radio Control Systems Battery Operated Equipment Local Area Network (LAN) Receivers DESCRIPTION The TK11830 is a positive-to-negative DC-DC converter. This IC converts a positive input voltage into a regulated negative output voltage. This DC-DC converter features an On/Off function with an active low control. The internal voltage reference provides a stable output voltage which can be set from -0.5 to -12.5 V. The thermal protection feature provides oscillator shutdown in the event of an overload condition. The wide input voltage range of 2.5 to 15 V and a 60 mA output current capability allow flexible operation in a large number of applications. The TK11830 is available in a miniature SOT-23L surface mount package. Optimized Toko inductors are available. TK11830 Vref 20 P VFB GND VOSC CONTROL VIN ORDERING INFORMATION BLOCK DIAGRAM VFB GND VOSC TK11830M Tape/Reel Code THERMAL PROTECTION TAPE/REEL CODE TL: Tape Left COMP OSCILLATOR CONTROL REFERENCE VOLTAGE Vref CONTROL VIN January 1999 TOKO, Inc. Page 1 TK11830 ABSOLUTE MAXIMUM RATINGS Supply Voltage ......................................................... 16 V Operating Voltage ............................................ Min. 2.5 V Power Dissipation (Note 1) ................................ 400 mW Storage Temperature Range ................... -55 to +150 C Operating Temperature Range ...................-20 to +75 C Junction Temperature ........................................... 150 C Lead Soldering Temperature (10 s) ...................... 235 C TK11830 ELECTRICAL CHARACTERISTICS SYMBOL VIN Vref Vref IIN(OFF) Line Reg Load Reg IOUT PARAMETER Input Voltage Reference Voltage Temperature Coefficient of Reference Voltage Input Current at Shutdown Line Regulation Load Regulation Output Current Test Conditions: VIN = 5 V, L = 470 H, TA = 25 C, unless otherwise specified. TEST CONDITIONS VIN + |VOUT| 16 V MI N 2.5 1.23 TYP MAX 15 UNITS V V mV/ C 1.28 0.1 1.33 TA = -30 to +80 C RCONT = 300 k, Output OFF, VIN = 5 V VIN = 2.5 to 10 V, VOUT = -5 V, IOUT = 20 mA VOUT = -5 V, IOUT = 1 to 50 mA VOUT = -5 V 50 25 10 20 60 100 50 100 A mV mV mA ON/OFF CONTROL TERMINAL ICONT VCONT(ON) VCONT(OFF) Control Terminal Current Control Voltage (ON) Control Voltage (OFF) VCONT = 0.4 V, RCONT = 300 k VCONT = 5.0 V, RCONT = 300 k RCONT = 300 k, Output ON RCONT = 300 k, Output OFF 2.2 3.0 0.4 0.2 A A V V Note 1: Power dissipation is 400 mW (internally limited) when mounted as recommended. Derate at 3.2 mW/C for operation above 25 C. Gen Note: Output capacitor should have low ESR at reduced temperatures if used below 0 C. Gen Note: Parameters with min. or max. values are 100% tested at TA = 25 C. Page 2 January 1999 TOKO, Inc. TK11830 TEST CIRCUIT Cref 1 F R1 20 k Note: Toko Inductor (470 H): 646CY-471M or 636CE-471K (D73C) VOUT = (Vref / 5) x [ 1-4 x (R2 / R1)], where Vref = 1.28 V VCONT (ON/OFF) +VIN + Vref RCONT CONTROL 300 k VIN VFB GND VOSC CFB 0.1 F SD Note: If a noise filter is desired, select: RF = (50 to 150 mV) / IOUT, where IOUT = Load Current R2 103 K VOUT RF VO CIN 47 F GND L + COUT 47 F CF GND TYPICAL PERFORMANCE CHARACTERISTICS OUTPUT VOLTAGE VS. LOAD CURRENT -3.1 -3.0 VOUT (V) OUTPUT VOLTAGE AND EFFICIENCY VS. LOAD CURRENT -5.1 VOUT -5.0 VOUT (V) VOUT = -3 V VIN = 8 V VOUT = -5 V VIN = 3 V 100 -2.9 -2.8 -2.7 -2.6 VIN = 3 V VIN = 5 V -4.9 50 -4.8 -4.7 -4.6 EFFICIENCY 0 20 40 60 80 100 0 6 12 18 24 30 ILOAD (mA) OUTPUT VOLTAGE VS. LOAD CURRENT -5.1 -5.0 VOUT (V) VOUT (V) ILOAD (mA) OUTPUT VOLTAGE AND EFFICIENCY VS. LOAD CURRENT -5.1 VOUT -5.0 VOUT = -5 V VIN = 5 V 100 VOUT = -5 V -4.9 -4.8 -4.7 -4.6 VIN = 3 V VIN = 5 V VIN = 8 V -4.9 50 -4.8 -4.7 -4.6 EFFICIENCY 0 20 40 60 80 100 0 10 20 30 40 50 ILOAD (mA) ILOAD (mA) January 1999 TOKO, Inc. EFF (%) EFF (%) Page 3 TK11830 TYPICAL PERFORMANCE CHARACTERISTICS (CONT.) OUTPUT VOLTAGE VS. LOAD CURRENT -10.0 -9.9 VOUT (V) VOUT (V) OUTPUT VOLTAGE AND EFFICIENCY VS. LOAD CURRENT -5.1 VOUT -5.0 VOUT = -5 V VIN = 10 V 100 VOUT = -10 V -9.8 -9.7 -9.6 -9.5 VIN = 3 V -4.9 50 -4.8 -4.7 -4.6 EFFICIENCY VIN = 5 V 0 20 40 60 80 100 0 20 40 60 80 100 ILOAD (mA) OUTPUT VOLTAGE VS. LOAD CURRENT -5.1 -5.0 VOUT (V) VOUT (V) -4.9 -4.8 -4.7 -4.6 VIN = 3 V VIN = 5 V VIN = 8 V TA = -50 C VOUT = -5 V ILOAD (mA) OUTPUT VOLTAGE AND EFFICIENCY VS. INPUT VOLTAGE -5.1 -5.0 -4.9 -4.8 -4.7 -4.6 EFF (%) EFF (%) TA = -50 C 100 ILOAD = 20 mA ILOAD = 10 mA EFFICIENCY 50 0 20 40 60 80 100 0 4 8 12 16 20 ILOAD (mA) VIN (V) OUTPUT VOLTAGE VS. LOAD CURRENT -5.1 -5.0 VOUT (V) VOUT (V) OUTPUT VOLTAGE AND EFFICIENCY VS. INPUT VOLTAGE -5.1 -5.0 TA = 25 C 100 TA = 25 C VOUT = -5 V -4.9 -4.8 -4.7 -4.6 VIN = 3 V VIN = 5 V VIN = 8 V -4.9 -4.8 -4.7 -4.6 ILOAD = 20 mA 50 EFFICIENCY ILOAD = 10 mA 0 20 40 60 80 100 0 4 8 12 16 20 ILOAD (mA) VIN (V) Page 4 January 1999 TOKO, Inc. EFF (%) TK11830 TYPICAL PERFORMANCE CHARACTERISTICS (CONT.) OUTPUT VOLTAGE VS. LOAD CURRENT -5.1 -5.0 VOUT (V) VOUT (V) OUTPUT VOLTAGE AND EFFICIENCY VS. INPUT VOLTAGE -5.1 -5.0 TA = 85 C 100 TA = 85 C VOUT = -5 V -4.9 -4.8 -4.7 -4.6 VIN = 3 V VIN = 5 V VIN = 8 V -4.9 -4.8 -4.7 -4.6 ILOAD = 20 mA 50 EFFICIENCY 0 20 40 60 80 100 0 4 8 12 16 20 ILOAD (mA) OUTPUT VOLTAGE VS. INPUT VOLTAGE -5.1 -5.0 IIN(OFF) (A) VOUT (V) VIN (V) INPUT CURRENT (SHUTDOWN) VS. INPUT VOLTAGE 100 IOFF TA = -50 C ILOAD = 0 mA, 10 mA, 20 mA 80 VIN EFF (%) VIN CONTROL 1 RCONT -4.9 -4.8 -4.7 -4.6 60 40 20 0 2 300 k 1.0 V 0 1 2 3 4 5 0 4 8 12 16 20 VIN (V) VIN (V) OUTPUT VOLTAGE VS. INPUT VOLTAGE -5.1 -5.0 VOUT (V) OUTPUT VOLTAGE AND CONTROL CURRENT VS. CONTROL VOLTAGE -5 VOUT -4 5 4 VIN VOUT CONTROL ICONT RCONT TA = 25 C ILOAD = 0 mA, 10 mA, 20 mA -4.9 -4.8 -4.7 -4.6 -3 -2 -1 0 TA = 25 C TA = -50 C 3 2 1 0 ICONT (A) VOUT (V) TA = 85 C 300 k VCONT 0 1 2 3 4 5 0 0.4 0.8 1.2 1.6 2.0 VIN (V) VCONT (V) January 1999 TOKO, Inc. Page 5 TK11830 TYPICAL PERFORMANCE CHARACTERISTICS (CONT.) OUTPUT VOLTAGE VS. INPUT VOLTAGE -5.1 -5.0 VOUT (V) OUTPUT VOLTAGE AMD CONTROL VOLTAGE VS. CONTROL CURRENT -5 -4 VOUT VCONT (V) ILOAD = 0 mA, 10 mA, 20 mA TA = 25 C 1.0 VIN CONTROL VOUT -4.9 -4.8 -4.7 -4.6 TA = 85 C VOUT (V) -3 0.5 -2 -1 0 ICONT 0 1 2 3 4 5 0 1 2 3 4 5 VIN (V) REFERENCE VOLTAGE VS. INPUT VOLTAGE 1.29 ICONT (A) REFERENCE VOLTAGE VS. AMBIENT TEMPERATURE 1.30 1.29 Vref (V) Vref (V) 0 3 6 9 12 15 1.28 1.27 1.26 1.28 1.27 1.25 -50 0 TA (C) 50 100 VIN (V) Page 6 January 1999 TOKO, Inc. TK11830 CIRCUIT OPERATION The TK11830 operates with a continuous mode oscillator. The circuit operates by detecting the difference between the set output voltage and the internal bandgap reference. This is used to vary the oscillator frequency in response to load current. The output voltage is regulated by controlling the power transistor switch current; this maintains a constant charge on the output capacitor. ~VIN Inductor Voltage ~VOUT Frequency goes up when the load current goes down. Inductor Current ILPK(MAX) Power - Transistor Maximum Absolute Output Voltage Set Output Voltage Low Load Current Start High Load Current Time January 1999 TOKO, Inc. Page 7 TK11830 CIRCUIT OPERATION (CONT.) POLARITY-INVERTING OPERATION VSAT VF ILOAD VOUT IL OSCILLATOR CONTROL IC VSAT VF IL IC ILOAD VL where: Power Transistor Saturation Voltage Diode Forward Voltage Drop Inductor Current Capacitor Current Load Current Inductor Voltage VIN L + COUT VL = L x (diL / dt) and VL = a constant value: IL = (VL / L) x t During the charge cycle: ILPK = [(VIN - VSAT) x tON] / L (1) During the discharge cycle: ILPK = [(|VOFF| + VF) x tOFF] / L (IL = 0 after tOFF) (2) From (1) and (2): INDUCTOR VOLTAGE VIN - VSAT ON OFF -(|VOUT| + VF) IL ILPK tON tOFF tON / tOFF = (|VOUT| + VF) / (VIN - VSAT) (3) CHARGE DISCHARGE Q+ = Q1- + Q2And: ILPK = 2 x ILOAD x [(tON / tOFF) + 1] (4) Ripple Voltage: VRIPPLE = Q+ / COUT = (ILPK - ILOAD)2 x tOFF / 2COUT x ILPK ~ ILOAD x tON / COUT (5) CAPACITOR CURRENT When IL = IC + ILOAD and output voltage are in a steady state, the change of the charge/discharge must be equivalent, so: ILPK - ILOAD IC Q+ Q2ILOAD Q1- RIPPLE VOLTAGE VRIPPLE Page 8 January 1999 TOKO, Inc. TK11830 CIRCUIT OPERATION (CONT.) Oscillator Frequency: f = 1/(tON + tOFF) Where: Output Voltage is as follows: tON = L x [ILPK / (VIN - VSAT)] And: tOFF = L x [ILPK / (|VOUT| + VF)] The ESR of the capacitor and the effect of the input voltage difference for the comparator function are added to VRIPPLE. The maximum inductor current is limited by the power transistor switch capacity: ILPK(MAX) ~ 300 mA. VOUT = (Vref / 5) x (1 - 4 x R2 / R1) where: Vref = 1.28 V R3, R4: IC Internal R4 / R3 = 1 / 4 R1, R2 : External Resistor Therefore: f= 1 1 1 I LPK L x + VIN - VSAT VOUT + VF R3 R1 Vref = 2I LOAD (VIN - VSAT + VOUT + VF ) (VIN - VSAT )2 ( VOUT + VF ) 2 x 1 L R4 R2 VOUT tON / tOFF (|VOUT| + VF) / (VIN - VSAT) ILPK 2 x ILOAD x [(tON / tOFF) + 1] f 2I LOAD (VIN - VSAT + VOUT + VF ) (VIN - VSAT )2 ( VOUT + VF ) 2 * 1 L COUT (ILOAD x tON) / VRIPPLE January 1999 TOKO, Inc. Page 9 TK11830 APPLICATION INFORMATION COMPONENT REQUIREMENTS Inductor DC resistance of the inductor must be less than 5 . For optimal performance and efficiency, an inductor with a DC resistance of less than 1 is recommended. The oscillator frequency is inversely proportional to inductance. The inductance should be greater than 300 H to prevent loss of efficiency at high frequencies. There is a large peak current (up to ILPK = 300mA) when the inductor is saturated. Input requirements of the Control pin are as follows: Control Pin Resistor (RCONT) RCONT 30 k VCONT + ICONT VBE ILPK L(SMALL) IL L(LARGE) ILPK(MAX) -300 mA INDUCTOR SATURATION t t When VCONT is high (above 2.2 V), the circuit operation is stopped. When VCONT is low (below 0.4 V), operation is resumed. A control current of 3 A (typ.) is required for shutdown. Shutdown voltage, VCONT, is related to the resistance RCONT as shown below. VCONT changes when RCONT is changed. VCONT ~ RCONT x ICONT + VBE VCONT ~ (300 k) x (3 A) + 0.7 V = 1.60 V at RSD = 300 k and VBE ~ 0.7 V CFB, CREF, CIN, COUT The filtered output ripple is fed back to the feedback pin. To ensure continuous operation, CFB should be connected between the feedback pin and ground. If a large voltage is fed back to the feedback pin, the power transistor switch drive will be intermittent. This causes a large ripple voltage since ILPK becomes larger. The value of CFB is determined by the value of the output capacitor, COUT, and the feedback resistance, R2. The feedback capacitor must be larger when the ripple voltage is high due to the lower COUT. CREF is used to prevent oscillation of the band gap reference and to stabilize the feedback loop. The input capacitor, CIN, is used to reduce supply impedance and to provide sufficient input current during switching for stable circuit operation. ON/OFF CONTROL -5 -4 VOUT (V) TA = 25 C 5 4 3 2 1 0 ICONT (A) -3 -2 -1 0 0 1 VCONT 2 Recommended values: CREF > 0.1 F CFB > 0.01 F CIN > 22 F COUT > 22 F Note: COUT should be sufficiently large and have a low ESR to minimize ripple voltage. Page 10 January 1999 TOKO, Inc. TK11830 APPLICATION INFORMATION (CONT.) INTERMITTENT OSCILLATION When the ripple voltage applied to the feedback pin is large and CFB is small, the power transistor switch drive is large and the output voltage exceeds the desired value. This causes the oscillator to stop for a period of ti. When the ripple voltage is large and the power transistor is driven at maximum capacity, a current up to ILPK(MAX) goes through the inductor. INDUCTOR CURRENT ILPK(MAX) mounting. The package power dissipation curve on a printed circuit board is estimated as follows: When Pin 4 is connected to GND (Power transistor switch is at maximum conductance), all input power is dissipated by the IC at TA = room temperature. In this state Tj goes up to 150 C and thermal protection operates. Input power is defined as PIN = VIN x ILPK(MAX) -ILOAD IL tON tOFF ti CAPACITOR CURRENT IC Q+ PLOSS = PIN - POUT ILOAD Q1- Q2- = POUT x [(100 / E) - 1] = |VOUT| x ILOAD x [(100 / E) - 1] IIN VIN Vref VIN + + VOSC VFB t Note: tON/tOFF = (|VOUT| + VF) / (VIN - VSAT) tON = [ILPK(MAX) / (VIN - VSAT)] x L tOFF = [ILPK(MAX) / (|VOUT| + VF)] x L Since the charge of the capacitor is equivalent to the discharge (Q+ = Q1- + Q2-): ILPK(MAX) = 2 x ILOAD x [(tON / tOFF) + 1] + 2 x ILOAD x (ti / tOFF) ti = ([ILPK(MAX) / (2 x ILOAD)] x tOFF) - (tON + tOFF) f = 1 / (tON + tOFF + ti) When load current increases, ti becomes shorter. As in the case above, if the load current is too small, the power transistor becomes overdriven and intermittent oscillation will occur. PACKAGE POWER DISSIPATION The internal thermal protection circuit will operate when Tj is approximately 150 C. When thermal protection operates, the power transistor switch will cycle between on and off to keep Tj 150 C. Thermal resistance Oja is determined by January 1999 TOKO, Inc. t IIN IIN WAVEFORM WHEN THERMAL PROTECTION IS OPERATING Page 11 TK11830 APPLICATION INFORMATION (CONT.) PD (mW) Tj = 150 C 25 50 75 TA (C) 150 750 600 MOUNTED PD (mW) 450 300 150 0 0 50 TA (C) FREE AIR The components shown in the test circuit may be changed for different operating conditions (input/output voltage, output current, inductor type, etc.) The performance of the DC-DC converter depends largely on the coil in use. To optimize efficiency, a coil with a low DC resistance should be used, such as the Toko 646CY471M. Oscillation will begin with an inductor value as low as 100 H. However, if the Equivalent Series Resistance (ESR) is over 5 , oscillation may not occur. The input and output capacitors should have a low ESR and high capacity since there is a large ripple current present. For operation below 0 C, the capacitors should be selected for low ESR and good temperature stability at reduced temperatures. This is required to minimize ripple current. For low values of load current, a smaller coil can be used. For higher current, a large coil is needed to prevent saturation. When the coil saturates, the current increases dramatically, resulting in a severe overcurrent through the inductor. Please refer to the following drawings. INDUCTOR CURRENT WAVEFORM (NORMAL) 100 150 OU T 11830 R2 V OU T C OU T Di INDUCTOR CURRENT L R1 C FB 6 5 4 23.0 mm 0 .0 1 TK1 1 8 3 0 C REF 1 F 1 2 3 C IN ON /OFF RS D 300 k V IN GN D 17.5 mm TIME Page 12 INDUCTOR CURRENT + + TIME INDUCTOR CURRENT WAVEFORM (SATURATED INDUCTOR) January 1999 TOKO, Inc. TK11830 PACKAGE OUTLINE Marking Information Marking N0 SOT-23L (SOT-23L-6) TK11830 0.6 6 5 4 Marking 1.0 1 e 2 e 0.95 3 0.32 0.95 +0.15 - 0.05 0.1 M e 0.95 e 0.95 Recommended Mount Pad 3.5 +0.3 - 0.1 2.2 (3.4) 1.4 max 0.3 e1 3.0 1.2 +0.15 - 0.05 15 0 - 0.1 0.4 + 0.3 0.1 0.15 3.3 Dimensions are shown in millimeters Tolerance: x.x = 0.2 mm (unless otherwise specified) Toko America, Inc. Headquarters 1250 Feehanville Drive, Mount Prospect, Illinois 60056 Tel: (847) 297-0070 Fax: (847) 699-7864 TOKO AMERICA REGIONAL OFFICES Midwest Regional Office Toko America, Inc. 1250 Feehanville Drive Mount Prospect, IL 60056 Tel: (847) 297-0070 Fax: (847) 699-7864 Western Regional Office Toko America, Inc. 2480 North First Street , Suite 260 San Jose, CA 95131 Tel: (408) 432-8281 Fax: (408) 943-9790 Eastern Regional Office Toko America, Inc. 107 Mill Plain Road Danbury, CT 06811 Tel: (203) 748-6871 Fax: (203) 797-1223 Semiconductor Technical Support Toko Design Center 4755 Forge Road Colorado Springs, CO 80907 Tel: (719) 528-2200 Fax: (719) 528-2375 Visit our Internet site at http://www.tokoam.com The information furnished by TOKO, Inc. is believed to be accurate and reliable. However, TOKO reserves the right to make changes or improvements in the design, specification or manufacture of its products without further notice. TOKO does not assume any liability arising from the application or use of any product or circuit described herein, nor for any infringements of patents or other rights of third parties which may result from the use of its products. No license is granted by implication or otherwise under any patent or patent rights of TOKO, Inc. January 1999 TOKO, Inc. (c) 1999 Toko, Inc. All Rights Reserved IC-140-TK11830 0798O0.0K max Page 13 Printed in the USA |
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