TK11830 POSITIVE-TO-NEGATIVE DC-DC CONVERTER FEATURES APPLICATIONS ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Positive-to-Negative Converter Adjustable Output Voltage On/Off Control Thermal Protection Sensor Broad Operating Voltage Range Miniature Package (SOT-23L) 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. TK11830 Vref VFB CONTROL GND 20 P VOSC VIN The TK11830 is available in a miniature SOT-23L surface mount package. Optimized Toko inductors are available. ORDERING INFORMATION TK11830M BLOCK DIAGRAM GND VFB VOSC Tape/Reel Code THERMAL PROTECTION TAPE/REEL CODE COMP TL: Tape Left OSCILLATOR CONTROL REFERENCE VOLTAGE Vref January 1999 TOKO, Inc. CONTROL VIN 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 Test Conditions: VIN = 5 V, L = 470 µH, TA = 25 °C, unless otherwise specified. SYMBOL PARAMETER TEST CONDITIONS VIN + |VOUT| ≤16 V MI N TYP 2.5 MAX UNITS 15 V 1.33 V VIN Input Voltage Vref Reference Voltage ∆Vref Temperature Coefficient of Reference Voltage TA = -30 to +80 ° C IIN(OFF) Input Current at Shutdown RCONT = 300 kΩ, Output OFF, VIN = 5 V 25 100 µA Line Reg Line Regulation VIN = 2.5 to 10 V, VOUT = -5 V, IOUT = 20 mA 10 50 mV Load Reg Load Regulation VOUT = -5 V, IOUT = 1 to 50 mA 20 100 mV IOUT Output Current VOUT = -5 V 1.23 1.28 mV/° C ±0.1 50 60 mA ON/OFF CONTROL TERMINAL VCONT = 0.4 V, RCONT = 300 kΩ ICONT Control Terminal Current VCONT(ON) Control Voltage (ON) RCONT = 300 kΩ, Output ON VCONT(OFF) Control Voltage (OFF) RCONT = 300 kΩ, Output OFF 0.2 VCONT = 5.0 V, RCONT = 300 kΩ 3.0 µA 0.4 2.2 µA 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 µF Note: Toko Inductor (470 µH): 646CY-471M or 636CE-471K (D73C) VOUT = (Vref / 5) x [ 1-4 x (R2 / R1)], where Vref = 1.28 V Vref R1 20 k Note: If a noise filter is desired, select: RF = (50 to 150 mV) / IOUT, where IOUT = Load Current VFB RCONT CONTROL GND CFB 0.1 µF 300 kΩ VOSC SD VCONT (ON/OFF) VIN R2 103 KΩ RF VOUT VO +VIN + CIN 47 µF L + COUT 47 µF CF GND GND TYPICAL PERFORMANCE CHARACTERISTICS OUTPUT VOLTAGE VS. LOAD CURRENT VOUT = -3 V VIN = 3 V -2.8 VIN = 5 V -2.7 0 20 40 60 80 -4.9 50 EFFICIENCY -4.8 -4.7 -4.6 100 0 6 12 24 30 ILOAD (mA) OUTPUT VOLTAGE VS. LOAD CURRENT OUTPUT VOLTAGE AND EFFICIENCY VS. LOAD CURRENT VOUT = -5 V VIN = 5 V -5.1 VOUT = -5 V VOUT 100 VOUT (V) -4.9 VIN = 3 V VIN = 5 V -4.8 VIN = 8 V -4.7 0 20 40 60 ILOAD (mA) January 1999 TOKO, Inc. 80 100 -4.9 50 EFFICIENCY -4.8 EFF (%) -5.0 -5.0 VOUT (V) 18 ILOAD (mA) -5.1 -4.6 100 -5.0 VOUT (V) -2.9 -2.6 VOUT VIN = 8 V -3.0 VOUT = -5 V VIN = 3 V -5.1 EFF (%) -3.1 VOUT (V) OUTPUT VOLTAGE AND EFFICIENCY VS. LOAD CURRENT -4.7 -4.6 0 10 20 30 40 50 ILOAD (mA) Page 3 TK11830 TYPICAL PERFORMANCE CHARACTERISTICS (CONT.) OUTPUT VOLTAGE AND EFFICIENCY VS. LOAD CURRENT OUTPUT VOLTAGE VS. LOAD CURRENT VOUT = -10 V -10.0 VOUT = -5 V VIN = 10 V -5.1 VOUT VOUT (V) VIN = 5 V -9.7 0 20 40 60 80 -4.6 100 60 80 100 OUTPUT VOLTAGE AND EFFICIENCY VS. INPUT VOLTAGE TA = -50 °C VOUT = -5 °V TA = -50 °C -5.1 100 -4.9 VIN = 3 V VIN = 5 V -4.8 VIN = 8 V 0 20 40 60 80 ILOAD = 20 mA -4.9 50 ILOAD = 10 mA -4.8 EFFICIENCY -4.7 -4.6 100 0 4 8 12 16 20 ILOAD (mA) VIN (V) OUTPUT VOLTAGE VS. LOAD CURRENT OUTPUT VOLTAGE AND EFFICIENCY VS. INPUT VOLTAGE TA = 25 °C VOUT = -5 °V -5.1 EFF (%) -5.0 VOUT (V) VOUT (V) 40 OUTPUT VOLTAGE VS. LOAD CURRENT -4.7 TA = 25 °C -5.1 -5.0 100 -5.0 -4.9 VOUT (V) VOUT (V) 20 ILOAD (mA) -5.0 VIN = 3 V VIN = 5 V -4.8 VIN = 8 V -4.7 0 20 40 60 ILOAD (mA) Page 4 0 ILOAD (mA) -5.1 -4.6 50 EFFICIENCY -4.8 -4.7 -9.6 -4.6 -4.9 80 100 ILOAD = 20 mA -4.9 50 -4.8 EFFICIENCY ILOAD = 10 mA -4.7 -4.6 EFF (%) VOUT (V) VIN = 3 V -9.8 EFF (%) -5.0 -9.9 -9.5 100 0 4 8 12 16 20 VIN (V) January 1999 TOKO, Inc. TK11830 TYPICAL PERFORMANCE CHARACTERISTICS (CONT.) OUTPUT VOLTAGE VS. LOAD CURRENT OUTPUT VOLTAGE AND EFFICIENCY VS. INPUT VOLTAGE TA = 85 °C VOUT = -5 °V -5.1 VIN = 3 V VIN = 5 V -4.8 VIN = 8 V 0 20 40 60 80 50 EFFICIENCY -4.8 -4.7 -4.6 100 0 4 8 12 16 20 ILOAD (mA) VIN (V) OUTPUT VOLTAGE VS. INPUT VOLTAGE INPUT CURRENT (SHUTDOWN) VS. INPUT VOLTAGE TA = -50 °C ILOAD = 0 mA, 10 mA, 20 mA -5.1 ILOAD = 20 mA -4.9 EFF (%) -4.9 -4.7 100 IOFF -5.0 80 IIN(OFF) (µA) VOUT (V) 100 -5.0 VOUT (V) VOUT (V) -5.0 -4.6 TA = 85 °C -5.1 -4.9 -4.8 VIN CONTROL VIN 60 1 40 2 RCONT 300 k 1.0 V -4.7 0 1 2 3 4 0 5 12 16 20 OUTPUT VOLTAGE AND CONTROL CURRENT VS. CONTROL VOLTAGE 5 -5 VOUT -4 VOUT (V) VOUT (V) 8 OUTPUT VOLTAGE VS. INPUT VOLTAGE -5.0 -4.9 -4.8 -3 TA = 25 °C 3 -2 TA = -50 °C 2 0 0 1 2 3 VIN (V) January 1999 TOKO, Inc. 4 5 VIN 4 TA = 85 °C 1 -1 -4.7 -4.6 4 VIN (V) TA = 25 °C ILOAD = 0 mA, 10 mA, 20 mA -5.1 0 VIN (V) ICONT (µA) -4.6 20 VOUT CONTROL ICONT RCONT 300 k VCONT 0 0 0.4 0.8 1.2 1.6 2.0 VCONT (V) Page 5 TK11830 TYPICAL PERFORMANCE CHARACTERISTICS (CONT.) OUTPUT VOLTAGE VS. INPUT VOLTAGE OUTPUT VOLTAGE AMD CONTROL VOLTAGE VS. CONTROL CURRENT -5.0 TA = 85 °C -4.9 -4.8 1.0 VOUT -4 VOUT (V) VOUT (V) TA = 25 °C -5 VIN -3 0.5 -2 VOUT CONTROL VCONT (V) ILOAD = 0 mA, 10 mA, 20 mA -5.1 ICONT -4.7 -4.6 -1 0 1 2 3 4 0 5 0 1 2 3 4 VIN (V) ICONT (µA) REFERENCE VOLTAGE VS. INPUT VOLTAGE REFERENCE VOLTAGE VS. AMBIENT TEMPERATURE 1.29 5 1.30 Vref (V) Vref (V) 1.29 1.28 1.28 1.27 1.26 1.27 0 3 6 9 VIN (V) Page 6 12 15 1.25 -50 0 50 100 TA (°C) 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. Inductor Voltage AAA AA ~VIN ~VOUT Absolute Output Voltage Inductor Current Frequency goes up when the load current goes down. ILPK(MAX) Power - Transistor Maximum AAAAAAAAAAAAAA A A A A Low Load Current Set Output Voltage High Load Current Start Time January 1999 TOKO, Inc. Page 7 TK11830 CIRCUIT OPERATION (CONT.) POLARITY-INVERTING OPERATION VSAT VSAT VF IL IC ILOAD VL Power Transistor Saturation Voltage Diode Forward Voltage Drop Inductor Current Capacitor Current Load Current Inductor Voltage VF ILOAD VOUT VIN IL OSCILLATOR CONTROL IC L COUT + where: VL = L x (diL / dt) and VL = a constant value: IL = (VL / L) x t INDUCTOR VOLTAGE VIN - VSAT During the charge cycle: ILPK = [(VIN - VSAT) x tON] / L ON -(|VOUT| + VF) OFF (1) During the discharge cycle: ILPK = [(|VOFF| + VF) x tOFF] / L (IL = 0 after tOFF) IL (2) ILPK From (1) and (2): tON tON / tOFF = (|VOUT| + VF) / (VIN - VSAT) CHARGE When IL = IC + ILOAD and output voltage are in a steady state, the change of the charge/discharge must be equivalent, so: ∆Q+ = ∆Q1- + ∆Q2And: CAPACITOR CURRENT (3) tOFF DISCHARGE ILPK - ILOAD IC ∆Q+ ∆Q2ILOAD ∆Q1- ILPK = 2 x ILOAD x [(tON / tOFF) + 1] Ripple Voltage: VRIPPLE = ∆Q+ / COUT = (ILPK - ILOAD)2 x tOFF / 2COUT x ILPK ~ ILOAD x tON / COUT RIPPLE VOLTAGE (4) VRIPPLE (5) Page 8 January 1999 TOKO, Inc. TK11830 CIRCUIT OPERATION (CONT.) Oscillator Frequency: 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. f = 1/(tON + tOFF) Where: Output Voltage is as follows: tON = L x [ILPK / (VIN - VSAT)] VOUT = (Vref / 5) x (1 - 4 x R2 / R1) And: tOFF = L x [ILPK / (|VOUT| + VF)] 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 × + VIN − VSAT VOUT + VF Vref R3 = (VIN − VSAT )2 ( VOUT + VF ) 2I LOAD (VIN − VSAT + VOUT + VF ) 2 × 1 L R1 R4 R2 VOUT tON / tOFF (|VOUT| + VF) / (VIN - VSAT) ILPK 2 x ILOAD x [(tON / tOFF) + 1] f COUT (VIN − VSAT )2 ( VOUT + VF ) 2I LOAD (VIN − VSAT + VOUT + VF ) 2 • 1 L (ILOAD x tON) / VRIPPLE January 1999 TOKO, Inc. Page 9 TK11830 APPLICATION INFORMATION COMPONENT REQUIREMENTS Control Pin Resistor (RCONT) Inductor DC resistance of the inductor must be less than 5 Ω. For optimal performance and efficiency, an inductor with a DC resistance of less than 1 Ω is recommended. The oscillator frequency is inversely proportional to inductance. The inductance should be greater than 300 µH to prevent loss of efficiency at high frequencies. Input requirements of the Control pin are as follows: RCONT VCONT + 30 k VBE ICONT There is a large peak current (up to ILPK = 300mA) when the inductor is saturated. ILPK ILPK(MAX) -300 mA IL INDUCTOR SATURATION 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. t CFB, CREF, CIN, COUT A control current of 3 µA (typ.) is required for shutdown. Shutdown voltage, VCONT, is related to the resistance RCONT as shown below. VCONT changes when RCONT is changed. 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. VCONT ~ RCONT x ICONT + VBE VCONT ~ (300 kΩ) x (3 µA) + 0.7 V = 1.60 V at RSD = 300 kΩ and VBE ~ 0.7 V ON/OFF CONTROL TA = 25 °C -5 5 4 -3 3 -2 2 CIN > 22 µF -1 1 COUT > 22 µF 0 Recommended values: CREF > 0.1 µF CFB > 0.01 µF Note: COUT should be sufficiently large and have a low VOUT (V) -4 ICONT (µA) L(LARGE) L(SMALL) 0 0 1 2 VCONT ESR to minimize ripple voltage. Page 10 January 1999 TOKO, Inc. TK11830 APPLICATION INFORMATION (CONT.) mounting. The package power dissipation curve on a printed circuit board is estimated as follows: INTERMITTENT OSCILLATION INDUCTOR CURRENT 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. ILPK(MAX) PLOSS, must be within this curve. The efficiency, E (%), is the ratio between input and output power when the dc-dc converter is operating. IL tON tOFF 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 <IIN>, where <IIN> is the average of input current. From Tj = Oja x P + TA and Tj = 150 °C. P = PIN, TA = Room temp., Oja can be found. The power dissipation curve shows the effect of mounting on thermal characteristics. ti CAPACITOR CURRENT ILPK(MAX) -ILOAD IC PLOSS = PIN - POUT ∆Q+ ∆Q1- = POUT x [(100 / E) - 1] ILOAD ∆Q2- = |VOUT| x ILOAD x [(100 / E) - 1] t Note: tON/tOFF = (|VOUT| + VF) / (VIN - VSAT) IIN tON = [ILPK(MAX) / (VIN - VSAT)] x L VIN tOFF = [ILPK(MAX) / (|VOUT| + VF)] x L Vref VIN + VOSC VFB + 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) TA = 25 °C MOUNTED ON PCB 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. IIN <IIN> 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 WAVEFORM WHEN THERMAL PROTECTION IS OPERATING Page 11 TK11830 APPLICATION INFORMATION (CONT.) 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 µH. However, if the Equivalent Series Resistance (ESR) is over 5 Ω, 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. PD (mW) Tj = 150 °C 25 50 75 TA (°C) 150 750 MOUNTED PD (mW) 600 450 FREE AIR 300 INDUCTOR CURRENT WAVEFORM (NORMAL) INDUCTOR CURRENT 150 0 0 50 100 150 TA (°C) V OU T + OU T 11830 C OU T R2 Di 6 5 4 0 .0 1 TK1 1 8 3 0 C REF 1 2 3 + 1 µF C IN ON /OFF RS D 300 k V IN GN D INDUCTOR CURRENT WAVEFORM (SATURATED INDUCTOR) INDUCTOR CURRENT L C FB R1 23.0 mm TIME 17.5 mm TIME Page 12 January 1999 TOKO, Inc. TK11830 PACKAGE OUTLINE Marking Information SOT-23L (SOT-23L-6) TK11830 Marking N0 0.6 6 5 4 e1 3.0 1.0 Marking 1 2 3 0.32 e +0.15 - 0.05 0.1 e 0.95 M e 0.95 e 0.95 3.5 0.95 Recommended Mount Pad +0.3 - 0.1 2.2 max 15 1.2 0.4 0.15 0.1 +0.15 - 0.05 0 - 0.1 1.4 max 0.3 (3.4) + 0.3 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. © 1999 Toko, Inc. All Rights Reserved Page 13 IC-140-TK11830 0798O0.0K Printed in the USA