Voltage Regulators AN8015SH Single-channel step-down, step-up, or inverting use DC-DC converter control IC Unit: mm 5 6 0.2±0.1 10 0.625±0.10 1 +0.1 0.15–0.05 0.5±0.2 4.3±0.30 ■ Features 6.3±0.30 0.625±0.10 1.5±0.2 0.1±0.1 0.5 The AN8015SH is a single-channel DC-DC converter control IC using the PWM method. This IC can provide any one output type from among step-down, step-up and inverting output. Its operating supply voltage range is wide and its consumption current is small. In addition, since it uses the 10-pin surface mounting type package with 0.5 mm pitch, it is suitable for highly efficient miniature potable power supply, especially for a negative output power supply. 3.0±0.30 ■ Overview • Wide operating supply voltage range (3.6 V to 34 V) • Small consumption current (1.8 mA typical) SSOP010-P-0225 • Converter control in a wide output frequency range is possible (2 kHz to 500 kHz). • Built-in timer latch short-circuit protection circuit (charge current 1.1 µA typical) • Incorporating the under-voltage lock-out (U.V.L.O.) circuit • Incorporating a high precision reference voltage circuit (2.46 V (allowance: ± 3%)) • Output block is open-collector (darlington) type. • High absolute maximum rating of output current (100 mA) • Maximum duty ratio is fixed and has small sample-to-sample variations (90% ± 5%). • Using 10-pin small outline package of 0.5 mm pitch ■ Applications FB 1.11 V VREF S.C.P. comp. 9 10 Out S R Latch 1.83 V R O U.V.L.O. 4 GND Clamp 3 IN− 8 I 5 S.C.P. IN+ 2 0.5 V Triangular wave OSC 1.2 V PWM comparator 0.37 V Reference supply 2.46 V (allowance : ± 3%) Error amp. RT CT VREF 1 6 ■ Block Diagram 7 VCC • LCD displays, digital still cameras, and PDAs 1 AN8015SH Voltage Regulators ■ Pin Descriptions Pin No. Symbol Description 1 CT Pin for connecting oscillator timing capacitor 2 RT Pin for connecting oscillator timing resistor 3 S.C.P. Pin for connecting the time constant setting capacitor for short-circuit protection 4 GND Grounding pin 5 Out Open collector type output pin 6 VCC Power supply voltage application pin 7 VREF Reference voltage output pin 8 IN+ Error amplifier noninverted input pin 9 IN− Error amplifier inverted input pin 10 FB Output pin of error amplifier ■ Absolute Maximum Ratings Parameter Symbol Rating Unit Supply voltage VCC 35 V IN− terminal allowable application voltage VIN− − 0.3 to VREF IN+ terminal allowable application voltage VIN+ − 0.3 to VREF Output terminal allowable application voltage VOUT 35 Collector output current IOUT 100 mA PD 154 mW Topr −30 to +85 °C Tstg −55 to +150 °C Power dissipation * Operating ambient temperature Storage temperature * * Note) *: Expect for the power dissipation, operating ambient temperature, and storage temperature, all ratings are for Ta = 25°C. ■ Recommended Operating Range Parameter Symbol Range Unit VIN − 0.1 to 0.8 V Collector output voltage VOUT 34 (maximum) V Collector output current IOUT 50 (maximum) mA Timing capacitance CT 100 to 27 000 pF Timing resistance RT 5.6 to 15 kΩ Oscillation frequency fOUT 2 to 500 kHz Reference voltage output current IRE −3 to 0 mA CSCP 1 000 (minimum) pF Error amplifier input voltage Soft start short-circuit protection time constant setting capacitance 2 Voltage Regulators AN8015SH ■ Electrical Characteristics at VCC = 12 V, RT = 15 Ω, CT = 200 pF, Ta = 25°C Parameter Symbol Conditions Min Typ Max Unit 2.386 2.46 2.534 V Reference voltage block Reference voltage VREF IREF = −1 mA Input regulation with input fluctuation Line VCC = 3.6 V to 34 V, IREF = −1 mA 5 20 mV Input regulation with input fluctuation 2 Line2 VCC = 3.6 V to 20 V 10 mV Load regulation Load IREF = − 0.1 mA to −1 mA 2 10 mV Output voltage temperature characteristics 1 VTC1 Ta = −30°C to +25°C ± 0.5 % Output voltage temperature characteristics 2 VTC2 Ta = 25°C to 85°C ± 0.5 % IRS −20 mA Circuit operation start voltage VUON 2.8 3.1 3.4 V Hysteresis width VHYS 100 200 300 mV VIO −6 6 mV IB −500 −25 nA Common-mode input voltage range VICR − 0.1 0.8 V High-level output voltage VEH V Low-level output voltage VEL Output sink current ISINK Reference short-circuit current U.V.L.O. block Error amplifier block Input offset voltage Input bias current Output source current Open-loop gain Common-mode ripple rejection ratio VREF − 0.3 VREF − 0.1 0.1 0.3 V VFB = 0.8 V 8 mA ISOURCE VFB = 0.8 V −120 µA AV 70 dB CMRR 50 dB Output block Oscillation frequency fOUT RT = 15 kΩ, CT = 200 pF 175 195 215 kHz Maximum duty ratio Dumax RT = 15 kΩ, CT = 200 pF 85 90 95 % Output saturation voltage VOL IO = 50 mA, RT = 15 kΩ 0.9 1.2 V Output leak current ILEAK VCC = 34 V, when output transistor is off 10 µA RT terminal voltage VRT 0.5 V 500 kHz Maximum oscillation frequency fOUT(max) RT = 5.6 kΩ, CT = 150 pF Frequency supply voltage characteristics fdV fOUT = 200 kHz, VCC = 3.6 V to 34 V ±2 % Frequency temperature characteristics 1 fdT1 fOUT = 200 kHz, Ta = −30°C to +25°C ±3 % Frequency temperature characteristics 2 fdT2 fOUT = 200 kHz, Ta = 25°C to 85°C ±3 % 3 AN8015SH Voltage Regulators ■ Electrical Characteristics at VCC = 12 V, RT = 15 Ω, CT = 200 pF, Ta = 25°C (continued) Parameter Symbol Conditions Min Typ Max Unit Short-circuit protection circuit block Input threshold voltage VTHPC 1.73 1.83 1.93 V Input standby voltage VSTBY 1.15 1.25 1.35 V Input latch voltage VIN 30 120 mV Charge current ICHG Comparator threshold voltage VTHL VSCP = 0 V −1.32 −1.1 − 0.88 µA 1.83 V Whole device Total consumption current ICC RT = 15 kΩ 1.8 2.8 mA Total consumption current 2 ICC2 RT = 5.6 kΩ, CT = 150 pF 2.5 mA ■ Terminal Equivalent Circuits Pin No. 1 Equivalent circuit VREF To PWM input IO OSC comp. 1 210 2 VREF 100 Ω Description I/O CT: The terminal used for connecting a timing capacitor to set oscillation frequency. Use a capacitance value within the range of 100 pF to 27 000 pF. Use a oscillation frequency in the range of 2 kHz to 500 kHz. O RT: The terminal used for connecting a timing resistor to set oscillation frequency. Use a resistance value within the range of 5.6 kΩ to 15 kΩ . The terminal voltage is 0.5 V typ. I S.C.P.: The terminal used for connecting a capacitor to set the time constant of soft start and timer latch shortcircuit protection circuit. Use a capacitance value in the range of more than 1 000 pF. The charge current is about 1.1 mA at RT = 15 kΩ VRT 1 ICHG = × [A] RT 30 O GND: Grounding terminal OSC PWM S.C.P. 2 RT(VRT ≈ 0.5 V) 3 VREF ICHG CT S.C.P. 1.83 V 3 4 4 4 PWM Latch S Q R Voltage Regulators AN8015SH ■ Terminal Equivalent Circuits (continued) Pin No. Equivalent circuit 5 VREF 5 6 VCC Out: Open-collector type (darlington) output terminal. The absolute maximum rating of output current is 100 mA Use with a steady-state output current under 50 mA. O VREF: The output terminal for the reference voltage (2.46 VREF overcurrent detection V) Use with a load current −3 mA or under. This terminal is incorporating the short-circuit protection circuit, and the short-circuit current is Bias to other block about −20 mA. Use the VREF for the reference 7 input setting of the error amplifier. O IN+: The noninverted input terminal of the error amplifier. For common-mode input, use in the range of − 0.1 V to +0.8 V. I IN−: The inverted input terminal of the error amplifier. For common-mode input, use in the range of − 0.1 V to +0.8 V. I FB: The output terminal of the error amplifier. The source current is about −120 µA, and the sink current is about 8 mA. Correct the frequency characteristics of the gain and the phase by connecting a resistor and a capacitor between this terminal and IN− terminal. O 8 VREF 9 9 10 I/O VCC: The terminal for applying supply voltage. Use with a operating supply voltage within the range of 3.6 V to 34 V. 6 7 Description 8 VREF 120 µA CT 8 mA 10 PWM 5 AN8015SH Voltage Regulators ■ Application Notes [1] Main characteristics Reference voltage temperature characteristics Maximum duty ratio temperature characteristics 91.0 2.50 VCC = 12 V CT = 200 pF RT = 15 kΩ Maximum duty ratio Dumax (%) Reference voltage VREF (V) VCC = 12 V IREF = −1 mA 2.49 2.48 2.47 2.46 2.45 −40 −20 0 20 40 60 89.5 20 40 60 80 100 Oscillation frequency temperature characteristics Timing capacitance Oscillation frequency 1M VCC = 12 V CT = 200 pF RT = 15 kΩ Oscillation frequency fOUT (Hz) 195 190 185 −20 0 20 40 60 80 100 k RT = 10 kΩ RT = 15 kΩ 10 k 1k 100 100 90 RT = 15 kΩ 80 100k Oscillation frequency fOUT (Hz) 10 000 100 000 Oscillation frequency Triangular wave maximum amplitude voltage Triangular wave maximum amplitude voltage (V) VCC = 12 V Ta = 25°C RT = 5.6 kΩ 70 10k 1 000 Timing capacitance CT (pF) Maximum duty ratio Oscillation frequency 100 VCC = 12 V Ta = 25°C RT = 5.6 kΩ Ambient temperature Ta (°C) Maximum duty ratio Dumax (%) 0 Ambient temperature Ta (°C) 180 −40 6 −20 Ambient temperature Ta (°C) 200 Oscillation frequency fOUT (kHz) 90.0 89.0 −40 100 80 90.5 1M 1.4 1.2 1.0 0.8 VCC = 12 V RT = 15 kΩ Ta = 25°C 0.6 0.4 0.2 0 10k 100k Oscillation frequency fOUT (Hz) 1M Voltage Regulators AN8015SH ■ Application Notes (continued) [1] Main characteristics (continued) Supply voltage Reference voltage 3.0 Supply voltage Total consumption current 3.0 Ta = 25°C IREF = −1 mA Total consumption current ICC (mA) Ta = 25°C Reference voltage VREF (V) 2.5 2.0 1.5 1.0 0.5 0 0 2 1 3 4 RT = 15 kΩ 1.5 1.0 0.5 1 0 2 3 5 4 Supply voltage VCC (V) Supply voltage VCC (V) Reference voltage line regulation Total consumption current line regulation 3.0 Ta = 25°C IREF = −1 mA Ta = 25°C Total consumption current ICC (mA) Reference voltage VREF (V) RT = 5.6 kΩ 2.0 0 5 2.52 2.50 2.48 2.46 2.44 2.42 0 10 5 15 20 25 30 2.5 RT = 5.6 kΩ 2.0 RT = 15 kΩ 1.5 35 0 5 10 15 20 25 30 35 Supply voltage VCC (V) Supply voltage VCC (V) Timing resistance Total consumption current Timing resistance Output saturation voltage 0.85 2.5 VCC = 12 V Ta = 25°C IO = 50 mA VCC = 12 V Ta = 25°C Output saturation voltage VOL (V) Total consumption current ICC (mA) 2.5 2.0 1.5 0.84 0.83 0.82 0.81 0.80 1.0 4 8 12 16 Timing resistance RT (kΩ) 20 4 8 12 16 20 Timing resistance RT (kΩ) 7 AN8015SH Voltage Regulators ■ Application Note (continued) [2] Timing chart 3.1 V typ. Lock-out release Supply voltage (VCC) 3.6 V VREF rise time tr (VREF) ≥ 10 [µs] Reference voltage (VREF) 2.46 V Error amplifier output (FB) Power supply on 1.83 V Triangular wave (CT) Dead-time voltage (VDT) 1.20 V 1.11 V 0.37 V High S.C.P. terminal voltage Output transistor collector waveform (Out) Low Soft start operation Maximum duty 90% Figure 1. PWM comparator operation waveform Reference voltage (VREF) 2.46 V Short-circuit protection input threshold level Comparator threshold level 1.83 V S.C.P. terminal voltage Dead-time voltage (VDT) 1.20 V 1.11 V Error amplifier output (FB) 0.37 V Triangular wave (CT) 0.03 V High Output transistor collector waveform (Out) Short-circuit protection comparator output Low tPE High Low Figure 2. Short-circuit protection operation waveform 8 Voltage Regulators AN8015SH ■ Application Notes (continued) [3] Function descriptions 1. Reference voltage block This block is composed of the band gap circuit, and outputs the temperature compensated 2.46 V reference voltage to the VREF terminal (pin 7). The reference voltage is stabilized when the supply voltage is 3.6 V or higher, and used as the operating power supply for the IC inside. It is possible to take out a load current of up to −3 mA . Also, an overcurrent protection circuit is built in for the load, thereby protecting the IC from destruction when VREF terminal is short circuited. 2. Triangular wave oscillation block The triangular wave which swings from the highest wave of approximately 1.4 V to the lowest wave of approximately 0.37 V will be generated by connecting a timing capacitor and a resistor to the CT terminal (pin 1) and RT terminal (pin 2) respectively. The oscillation frequency can be freely decided by the value of CT and RT connected externally. The triangular wave is connected with the inverted input of PWM comparator of the IC inside. 3. Error amplifier block This block detects the output voltage of DC-DC converter by the PNP transistor input type error amplifier, and inputs the amplified signal to the PWM comparator. The common-mode input voltage range is − 0.1 V to 0.8 V, and is a voltage obtained by dividing the reference voltage with resistors. Also, it is possible to perform the gain setting and the phase compensation arbitrarily by inserting the feedback resistor and capacitor between the error amplifier output terminal (pin 10) and the inverted input terminal (pin 9). The output voltage VOUT, if positive, is obtained by connecting the resistor-divided reference voltage to the noninverted input terminal as shown in figure 3. 1), and the output voltage VOUT, if negative, is obtained by connecting to the inverted input terminal as shown in figure 3. 2). The output voltages in each of these cases are given in the following equations. VOUT = VIN+ × R1 + R2 R2 VIN+ = VREF × R4 R3 + R4 R3 R2 R4 VREF 7 IN+ 8 R3 + R4 VREF R3 R2 R1 + R2 VREF 7 PWM comparator Error amp. input R1 R3 R2 R4 IN− 9 RNF IN+ 8 PWM comparator Error amp. input IN− 9 RNF VOUT CNF FB 10 R1 VIN− = VREF × FB 10 VOUT VOUT = − (VREF − VIN−) × CNF 1) If output is positive 2) If output is negative Figure 3. Connection method of error amplifier 4. Timer latch short-circuit protection circuit This circuit protects the external main switching devices, flywheel diodes, and choke coils, etc. from destruction or deterioration if overload or short-circuit of power supply output lasts for a certain time. The timer latch short-circuit protection circuit detects the output level of the error amplifier. When the output voltage of DC-DC converter drops and the output level of error amplifiers exceeds 1.85 V, the low-level output is given and the timer circuit is actuated to start the charge of the external protection enable capacitor. If the output of the error amplifier does not return to a normal voltage range by the time when the voltage of this capacitor reaches 1.83 V, it sets the latch circuit, cuts off the output drive transistor, and sets the dead-time at 100%. 9 AN8015SH Voltage Regulators ■ Application Notes (continued) [3] Function descriptions (continued) 5. Low input voltage malfunction prevention circuit (U.V.L.O.) This circuit protects the system from destruction or deterioration due to control malfunction when the supply voltage is low in the transient state of power on/off. The low input voltage malfunction prevention circuit detects the internal reference voltage which changes according to the supply voltage level. Until the supply voltage reaches 3.1 V during its rise time, it cuts off the the output drive transistor, sets the dead-time at 100% and holds the S.C.P. terminal (pin 3) to low level. During the fall time of the power supply voltage, it has hysteresis width of 200 mV and operates 2.9 V or less. 6. PWM comparator block The PWM comparator controls the on-period of the output pulse according to the input voltage. It turns on the output transistor during the period when the triangular wave of CT terminal (pin 1) of noninverted input is lower than any one of the following voltages : the voltage of the error amplifier output (pin 10) of the inverted input, S.C.P. terminal (pin 3), and the voltage for dead-time which is fixed inside the IC. The S.C.P. terminal voltage is kept at 1.25 V in the state in which DC-DC converter output is stabilized. However, when the power supply is turned on, the soft start is activated, which gradually extends on-period according to the time constant determined by the capacitance of externally attached capacitor and the charge current. The maximum duty ratio is fixed at approximately 90% by the voltage for dead-time. 7. Output block The output drive transistor is of open-collector type output connected in darlington circuit of emitter common GND. The breakdown voltage of collector output terminal (pin 5) is 34 V and it is possible to obtain up to 100 mA output current. [4] Triangular wave oscillation circuit 1. Oscillation frequency setting method The waveform of triangular wave oscillation is obtained by charging and discharging of the constant current IO from the external timing capacitor CT which is connected to CT terminal (pin 1). The constant current is set by the externally attached timing resistor RT . The peak value of the wave VCTH and the trough VCTH = 1.4 V typ. value of the wave VCTL are fixed at approximately 1.4 V typical and 0.37 V typical respectively. The oscillation frequency fOSC is obtained by the following formula; VCTL = 0.37 V typ. 1 IO t t 1 2 fOSC = = t1 + t 2 2 × CT × (VCTH − VCHL) Charging Discharging VRT 0.5 =2× whereas IO = 2 × RT RT T because VCTH − VCTL = 0.83 V Figure 4. Triangular wave oscillation waveform 1 fOSC = 1.66 × CT × RT The output frequency fOUT is equal to fOSC since it is PWM-controlled. 10 Voltage Regulators AN8015SH ■ Application Notes (continued) [4] Triangular wave oscillation circuit (continued) Oscillation frequency fOUT (Hz) 2. Usage notes This IC uses the constant current given by the timing resistor RT as the bias current of the triangular oscillation block and the PWM comparator for consumption current reduction. The total consumption current is approximately 1.8 mA (typical) when RT is 15 kΩ, and it increases to approximately 2.5 mA (typical) when RT is 5.6 k Ω. In order to obtain the steady-state output current of 100 mA at the open collector output, it is necessary to set RT value to 15 kΩ or smaller. It is possible to use the circuit in the recom1M mended operating range of 2 kHz to 500 kHz of the oscillation frequency. However, the timing resistor 500 k RT versus the oscillation frequency should be set Recommended operating within the recommended range shown in figure 5. condition 100 k Also, refer to the "Applications Notes, [1] Main characteristics, Timing capacitance Oscillation frequency" for setting the timing capacitance. 10 k For a high frequency use, the overshoot and undershoot amounts increase due to operation delay of the triangular oscillation comparator, and the maximum duty ratio drops. This effect can be alle1k viated by speeding up through the reduction of the 5 k 5.6 k 15 k 10 k resistor RT and increase in the circuit current. Timing resistance RT (Ω) Note that this IC can not be used as an IC for Figure 5. Timing resistance recommended condition slave when the several ICs are operated in parallel synchronous mode. [5] Time constant setting method for short-circuit protection circuit with joint-use of soft start/timer latch type The constructional block diagram of protection latch circuit is shown in figure 6. The comparator for short-circuit protection compares the output of error amplifier VFB with the reference voltage of 1.85 V at all the time. When the load conditions of DC-DC converter output is stabilized, there is no fluctuation of error amplifier output and the short-circuit protection comparator also keeps the balance. At this moment, the output transistor Q1 is in the conductive state and the S.C.P. terminal is hold to approximately 1.25 V through the clamp circuit. When the load conditions suddenly change, and high-level signal (1.85 V or higher) is input from the error amplifier to the noninverted input of the short-circuit protection comparator, the short-circuit protection comparator outputs the low-level signal. Since this signal cuts off the output transistor Q1, the S.C.P. terminal voltage VPE is released, and the externally connected capacitor CS starts charging according to the following equation: tPE [V] VPE = VSTBY + ICHG × CS 1.83 V = 1.25 V + ICHG × CS = ICHG × tPE CS tPE [F] 0.58 ICHG is the constant current determined by the oscillation timing resistor RT and its dispersion and fluctuation with temperature are small. ICHO is expressed in the following equation: ICHG = VRT 1 × [A] 30 RT VRT is approximately 0.5 V and ICHO becomes approximately 1.1 µA when RT = 15 kΩ. 11 AN8015SH Voltage Regulators ■ Application Notes (continued) [5] Time constant setting method for short-circuit protection circuit with joint-use of soft start/timer latch type (continued) When the external capacitor CS has been charged up to approximately 1.83 V, it sets the latch circuit, cuts off the output drive transistor by enabling the low input voltage malfunction prevention circuit, and sets the dead-time at 100%. The low input voltage malfunction prevention circuit is once enabled, the S.C.P. terminal voltage is discharged to approximately 30 mV but the latch circuit is not reset unless the power is turned off. The S.C.P. terminal voltage is inputted to the PWM comparator, and the soft start is actuated when the power turns on. However, since at the beginning of power on, the error amplifier output is high level, and VPE of S.C.P. terminal voltage is released and charging begins; the external capacitor should be set so that the output voltage of DC-DC convertor starts to rise before the latching circuit is set. The charging equation is as same as the above. The soft start time tSS until the input standby voltage VSTBY becomes 1.25 V is given in the following equations: 1.25 V = 0.03 V + ICHG × tSS = 1.22 × CS ICHG tSS CS VREF ICHG [s] Clamp circuit 1.25 V IN+ S.C.P. comp. Q2 Q1 9 10 S R Latch 1.83 V S.C.P. 3 IN− FB 8 Error amp. PWM comparator input CS Figure 6. Short-circuit protection circuit 12 R U.V.L.O. Output cut-off Voltage Regulators AN8015SH ■ Application Circuit Examples 1. Chopper method step-down type VCC 120 kΩ 0.1 µF 1 000 pF 8.2 kΩ 4.5 kΩ Out 5 6 VCC 7 VREF 0.1 µF VO 5V SBD GND 4 8 IN+ 15 kΩ S.C.P. 3 CT 1 RT 2 10 FB 9 IN− 3.6 kΩ 200 pF 25.5 kΩ 2. Chopper method inverting type 130 kΩ 120 kΩ 6 VCC Out 5 0.1 µF 7 VREF 8 IN+ S.C.P. 3 9 IN− 10 FB RT 2 15 kΩ VO −24 V 8.2 kΩ GND 4 9.1 kΩ 1 000 pF CT 1 SBD 0.1 µF 3.6 kΩ 200 pF VCC 13 AN8015SH Voltage Regulators ■ Application Circuit Examples (contined) 3. On/off circuit example VCC 1) Method to cut VCC line Standby current ≈ 0 µA S.C.P. 2) Method to cut S.C.P. line VO C8 SBD 6 VCC ICC Out 5 7 VREF GND 4 IN+ 8 S.C.P. 3 IN− 9 2 RT 10 FB C7 1 On/off C8 VCC Consumption current when output off ≈ 1.8 mA CT SBD Out 5 6 VCC 7 VREF Q1 ICC GND 4 IN+ 8 3 IN− 9 2 RT 10 CT 1 FB C7 VO Q2 On/off 4. Using method Since the on/off circuit is not incorporated in this IC, it is required to add on/off circuit externally to provide a standby function. When the switch (Q1) is inserted between the VCC line and the Vcc pin of the IC (pin 6) as shown in 3. 1), the standby current is suppressed to 0. When the output is turned off by decreasing the S.C.P. terminal voltage below the lower limit of the triangular wave (0.37 V typical) as shown in 3. 2), the consumption current does not decrease because the IC is operating. 5. Usage notes The rise time of the VCC becomes sharp especially in the case of 3. 1). At that time, there is a case that the internal latch circuit of the IC is set so that the circuit fails to start. Adjust C7 or C8 so that the rise time for VREF pin (pin 7) becomes 10 ms or longer. 14