AN8049SH PANASONIC
Document overview
- Manufacturer or author: Provided By digicamel.com
- PDF pages: 28
Technical content
1.8-volt 3-channel step-up, step-down, and polarity inverting DC-DC converter control IC n Overview The AN8049SH is a three-channel PWM DC-DC converter control IC that features low-voltage operation. This IC can form a power supply that provides two step- up outputs and one step-down or polarity inverted output with a minimal number of external components. The AN8049SH features the ability to operate from a supply voltage as low as 1.8 V, and thus can be operated from two dry-batteries. n Features
- Wide operating supply voltage range: 1.8 V to 14 V
- High-precision reference voltage circuit —V REF pin voltage: –1% — Error amplifier: –1.5%
- Surface mounting package for miniaturized and thinner power supplies Package: SSOP-24D 0.5-mm lead pitch 7.8 mm · 6.8 mm · t 1.9 mm
- Supports control over a wide output frequency range: 20 kHz to 1 MHz
- On/off (sequence control) pins provided for each channel for easy sequence control setup
- The negative supply error amplifier supports 0-volt input. Common-mode input voltage range: - 0.1 V to V CC -1.4 V This allows the number of external components to be reduced by two resistors.
- Fixed duty factor: 86% However, the duty can be adjusted to anywhere from 0% to 100% with an external resistor.
- Timer latch short-circuit protection circuit (charge current: 1.1 mA typical)
- Standby function (active-high control input, standby mode current: 1 mA maximum)
- Alternate package versions also available. Part No.: AN8049FHN Package: QFN-24 0.5-mm lead pitch 5.4 mm · 4.4 mm · t 0.8 mm n Applications
- Electronic equipment that requires a power supply system SSOP024-P-0300A Unit : mm 6.5±0.3 11 2 24 13 5.5±0.3 7.5±0.3 0.50(0.50) Seating plane Seating plane 0.2±0.1 0.65±0.100.65±0.10 1.5±0.20.1±0.1 (0.50) 0° to 10° 0.15 +0.10– 0.05
AN8049SH Voltage Regulators n Block Diagram IN-1 FB1 CTL17 V CC DT1 V REF OSC Off 20 kW 1.1 mA 1.26 V CTL3 DT3 IN-3 19IN+3 FB3 S.C.P. RB1 OUT1 OUT3 RB2 OUT2 GND IN-2 FB2 1.26 V Error amplifier 3 CTL2 DT2 31.26 V 1.26 V 1.1 mA 1.1 mA 1.1 mA 0.9 V Error amplifier 1 Error amplifier 2 44 kW56 kW V REF V CC 45 kW 55 kW V CCOn/off control Reference voltage supply V REF Sawtooth wave generator 0.7 V 0.3 V 1.26 V (Allowance: –1%) S.C.P. comp. Latch U.V .L.O. R S Q 1.26 V
1.26 V20 kW
Pin No. Symbol Description
12 OUT1 OUT1 block push-pull output
13 OUT2 OUT2 block push-pull output
14 GND Ground
15 OUT3 OUT3 block open-collector output
16 V CC Supply voltage
17 OSC Oscillator circuit timing resistor and
18 IN +3 Error amplifier 3 noninverting input
19 IN -3 Error amplifier 3 inverting input
20 FB3 Error amplifier 3 output
21 IN -2 Error amplifier 2 inverting input
22 FB2 Error amplifier 2 output
23 IN -1 Error amplifier 1 inverting input
24 FB1 Error amplifier 1 output
Pin No. Symbol Description 1 S.C.P. C onnection for the capacitor that provides the short- circuit protection circuit time constant
2 DT3 Channel 3 soft start setting
3 DT2 Channel 2 soft start setting
4 DT1 Channel 1 soft start setting
5 CTL3 Channel 3 on/off control
6 CTL2 Channel 2 on/off control
7 CTL1 Channel 1 on/off control
8 Off On/off control
9V REF Reference voltage output
10 RB2 Connection for the OUT2
block output source current setting resistor
11 RB1 Connection for the OUT1
block output source current setting resistor
Voltage Regulators AN8049SH Note) 1. Do not apply external currents or voltages to any pins not specifically mentioned. For circuit currents, '+' denotes current flowing into the IC, and '-' denotes current flowing out of the IC. 2. Items other than the storage temperature, operating temperature, and power dissipation are all stipulated for an ambient temperature Ta = 25°C. 3.*1: Ta = 85°C. See the "Application Notes" for details on the relationship between IC power dissipation and the ambient temperature. *2: When VCC < 6 V, the following condition must hold: VIN-1 = VIN-2 = VCC - 0.2 V. n Absolute Maximum Ratings Parameter Symbol Rating Unit Supply voltage V CC 14.2 V Off pin allowable application VOFF 14.2 V voltage CTL pin allowable application VCTL V CC - 0.2 V voltage Error amplifier input pin V IN 6V allowable application voltage *2 Supply current I CC ¾ mA OUT1 and OUT2 pin output I SO(OUT) -50 mA source current OUT3 pin output current I O +50 mA Power dissipation *1 PD 146 mW Operating temperature T opr -30 to +85 °C Storage temperature T stg -55 to +125 °C n Recommended Operating Range Parameter Symbol Range Unit Off pin application voltage V OFF 0 to 14 V OUT1 and OUT2 pin output source current I SO(OUT) -40 to -1m A OUT3 pin output current I O 40 (max.) Timing resistance R T 3 to 33 k W Timing capacitance C T 100 to 10 000 pF Oscillator frequency f OUT 20 to 1 000 kHz Short-circuit protection time-constant setting capacitance CSCP 1 000 (min.) pF Output current setting resistance R B 750 to 15 000 W
AN8049SH Voltage Regulators Parameter Symbol Conditions Min Typ Max Unit Reference voltage block Reference voltage V REF IREF = - 0.1 mA 1.247 1.26 1.273 V Line regulation with input fluctuationLine V CC = 1.8 V to 14 V ¾ 22 0 m V Load regulation Load I REF = - 0.1 mA to -1 mA -20 -3 ¾ mV U.V.L.O. block Circuit operation start voltage VUON 1.59 1.67 1.75 V Error amplifier 1 block Input threshold voltage 1 V TH1 1.241 1.26 1.279 V Input bias current 1 I B1 ¾ 0.1 0.2 mA High-level output voltage 1 V EH1 1.0 1.2 1.4 V Low-level output voltage 1 V EL1 ¾¾ 0.2 V Output source current 1 I SO(FB)1 -38 -31 -24 mA Output sink current 1 I SI(FB)1 0.5 ¾¾ mA Error amplifier 2 block Input threshold voltage 2 V TH2 1.241 1.26 1.279 V Input bias current 2 I B2 ¾ 0.1 0.2 mA High-level output voltage 2 V EH2 1.0 1.2 1.4 V Low-level output voltage 2 V EL2 ¾¾ 0.2 V Output source current 2 I SO(FB)2 -38 -31 -24 mA Output sink current 2 I SI(FB)2 0.5 ¾¾ mA Error amplifier 3 block Input offset voltage V IO -6 ¾ 6m V Common-mode input voltage range VICR - 0.1 ¾ V CC V -1.4 Input bias current 3 I B3 - 0.6 - 0.3 ¾m A High-level output voltage 3 V EH3 1.0 1.2 1.4 V Low-level output voltage 3 V EL3 ¾¾ 0.2 V Output source current 3 I SO(FB)3 -38 -31 -24 mA Output sink current 3 I SI(FB)3 0.5 ¾¾ mA Oscillator block Oscillator frequency f OUT R T = 7.5 kW , CT = 680 pF 170 190 210 kHz n Electrical Characteristics at VCC = 2.4 V, CREF = 0.1 mF, Ta = 25°C
Voltage Regulators AN8049SH Parameter Symbol Conditions Min Typ Max Unit Output 1 block Output duty factor 1 Du 1 R T = 7.5 kW , CT = 680 pF 80 86 92 % High-level output voltage 1 V OH1 IO = -10 mA, RB = 1 kW V CC -1 ¾¾ V Low-level output voltage 1 V OL1 IO = 10 mA, RB = 1 kW¾ ¾ 0.2 V Output source current 1 I SO(OUT)1 V O = 0.7 V, RB = 1 kW- 34 -29 -24 mA Output sink current 3 I SI(OUT)1 V O = 0.7 V, RB = 1 kW 40 ¾¾ mA Pull-down resistor 1 R O1 17 27 37 k W Output 2 block Output duty factor 2 Du 2 R T = 7.5 kW , CT = 680 pF 80 86 92 % High-level output voltage 2 V OH2 IO = -10 mA, RB = 1 kW V CC -1 ¾¾ V Low-level output voltage 2 V OL2 IO = 10 mA, RB = 1 kW¾ ¾ 0.2 V Output source current 2 I SO(OUT)2 V O = 0.7 V, RB = 1 kW- 34 -29 -24 mA Output sink current 2 I SI(OUT)2 V O = 0.7 V, RB = 1 kW 40 ¾¾ mA Pull-down resistor 2 R O2 17 27 37 k W Output 3 block Output duty factor 3 Du 3 R T = 7.5 kW , CT = 680 pF 80 86 92 % Output saturation voltage V O(SAT) IO = 40 mA ¾¾ 0.5 V Output leakage current I OLE V13 = 14 V ¾¾ 1 mA Short-circuit protection circuit block Input standby voltage V STBY ¾¾ 0.1 V Input threshold voltage V THPC 0.8 0.9 1.0 V Input latch voltage V IN ¾¾ 0.1 V Charge current I CHG V SCP = 0 V -1.43 -1.1 - 0.77 mA On/off control block Input threshold voltage V ON(TH) 0.6 0.9 1.2 V CTL block Input threshold voltage V THCTL 1.07 1.26 1.45 V Charge current I CTL V CTL = 0 V -1.43 -1.1 - 0.77 mA Whole Device Average consumption current I CC(OFF) R B = 9.1 kW , duty = 50% ¾ 4.2 5.5 mA Standby mode current I CC(SB) ¾¾ 1 mA n Electrical Characteristics at VCC = 2.4 V, CREF = 0.1 mF, Ta = 25°C (continued)
AN8049SH Voltage Regulators Parameter Symbol Conditions Min Typ Max Unit Reference voltage block V REF temperature characteristics VRFEdT Ta = -30°C to +85°C ¾ 1 ¾ % Error amplifier 1 block V TH temperature characteristics VTHdT1 Ta = -30°C to +85°C ¾ 1.5 ¾ % Open loop gain 1 A V1 ¾ 80 ¾ dB Error amplifier 2 block V TH temperature variation V THdT2 ¾ 1.5 ¾ % Open loop gain 2 A V2 ¾ 80 ¾ dB Error amplifier 3 block Open loop gain 3 A V3 ¾ 80 ¾ dB Oscillator block Frequency supply voltage f DV V CC = 1.8 V to 14 V ¾ 1 ¾ % characteristics R T = 7.5 kW , CT = 680 pF Frequency temperature f DT Ta = -30°C to +85°C ¾ 3 ¾% characteristics R T = 7.5 kW , CT = 680 pF Short-circuit protection circuit block Comparator threshold voltage V THL ¾ 1.26 ¾ V On/off control block Off pin current I OFF V OFF = 5 V ¾ 38 ¾m A n Electrical Characteristics at Ta = 25°C (continued)
- Design reference data Note: The characteristics listed below are reference values related to the IC design and are not guaranteed.
Voltage Regulators AN8049SH Pin No. Equivalent circuit Description I/O 1 S.C.P.: O Connection for the capacitor that sets the timer latch short-circuit protection circuit time constant. Use a capacitor with a value of 1 000 pF or higher. The charge current I CHG is 1.1 mA typical.
2 DT3: I
Sets the channel 3 soft start time. Set the time by connecting a capacitor between this pin and ground. (See the "Application Notes, [7]" section.) Note that although the channel 3 maximum on duty is set internally to 86%, the maximum on duty can be adjusted by connecting resistors between this pin and ground, and between this pin and the V REF pin. (See the "Application Notes, [6]" section.)
3 DT2: I
Sets the channel 2 soft start time. Set the time by connecting a capacitor between this pin and ground. (See the "Application Notes, [7]" section.) Note that although the channel 2 maximum on duty is set internally to 86%, the maximum on duty can be adjusted by connecting resistors between this pin and ground, and between this pin and the V REF pin. (See the "Application Notes, [6]" section.)
4 DT1: I
Sets the channel 1 soft start time. Set the time by connecting a capacitor between this pin and ground. (See the "Application Notes, [7]" section.) Note that although the channel 1 maximum on duty is set internally to 86%, the maximum on duty can be adjusted by connecting resistors between this pin and ground, and between this pin and the V REF pin. (See the "Application Notes, [6]" section.) n Terminal Equivalent Circuits 1.26 V V CC Latch S R Q 1.1 mA 1.5 kW Output shutoff 46 kW 44 kW PWM3 9 20 17 55 kW 45 kW PWM2 9 22 17 55 kW 45 kW PWM1 9 24 17
AN8049SH Voltage Regulators Pin No. Equivalent circuit Description I/O
5 CTL3: I
Controls the on/off state of channel 3. A delay can be provided in the power supply turn-on start time by connecting a capacitor between this pin and ground. (See the "Application Notes, [9]" section.) tDLY3 = 1.26 (V) · CCTL3 (mF)/1.1 (mA) (s) This pin can also be used to control the on/off state with an external signal. In that case, the allowable input voltage range is from 0 V to V CC . Note that during U.V.L.O. and timer latch operation, this pin is connected to ground through a 20 kW resistor.
6 CTL2: I
Controls the on/off state of channel 2. A delay can be provided in the power supply turn-on start time by connecting a capacitor between this pin and ground. (See the "Application Notes, [9]" section.) tDLY2 = 1.26 (V) · CCTL2 (mF)/1.1 (mA) (s) This pin can also be used to control the on/off state with an external signal. In that case, the allowable input voltage range is from 0 V to V CC . Note that during U.V.L.O. and timer latch operation, this pin is connected to ground through a 20 kW resistor.
7 CTL1: I
Controls the on/off state of channel 1. A delay can be provided in the power supply turn-on start time by connecting a capacitor between this pin and ground. (See the "Application Notes, [9]" section.) tDLY1 = 1.26 (V) · CCTL1 (mF)/1.1 (mA) (s) This pin can also be used to control the on/off state with an external signal. In that case, the allowable input voltage range is from 0 V to VCC . Note that during U.V.L.O. and timer latch operation, this pin is connected to ground through a 20 kW resistor. n Terminal Equivalent Circuits (continued) 1.26 V V CC 20 kW 1.1 mA High Channel 3 output operation 1.26 V V CC 20 kW 1.1 mA High Channel 2 output operation 1.26 V V CC 20 kW 1.1 mA High Channel 1 output operation
Voltage Regulators AN8049SH Pin No. Equivalent circuit Description I/O
8 Off: I
Controls the on/off state. When the input is high: normal operation OFF > 1.2 V) When the input is low: standby mode OFF < 0.6 V) In standby mode, the total current consumption is held to under 1 mA. 9V REF :O Outputs the internal reference voltage. The reference voltage is 1.26 V (allowance: –1%) when VCC is 2.4 V and IREF is - 0.1 mA. Insert a capacitor of at least 0.1 mF between V REF and ground for phase compensation.
10 RB2: I
Connection for a resistor that sets the channel 2 output current. Use a resistor in the range 750 W to 15 kW .
11 RB1: I
Connection for a resistor that sets the channel 1 output current. Use a resistor in the range 750 W to 15 kW . 12 See pin 11. OUT1: O Push-pull output. The absolute maximum rating for the output source current is -50 mA. The output source current is set by the external resistor connected to the RB1 pin. n Terminal Equivalent Circuits (continued) 100 kW Start and stop of internal circuits. V CC
200 W 30 kW
ISI(OUT)2 ISO(OUT)2 ISI(OUT)1 ISO(OUT)1
AN8049SH Voltage Regulators Pin No. Equivalent circuit Description I/O 13 See pin 10. OUT2: O Push-pull output. The absolute maximum rating for the output source current is -50 mA. The output source current is set by the external resistor connected to the RB2 pin.
14 GND: ¾
15 OUT3: O
Open-collector output. The absolute maximum rating for the output current is +50 mA.
16 V CC : ¾
Power supply. Provide the oprating supply voltage in the range 1.8 V to 14 V.
17 OSC: O
Connection for the capacitor and resistor that determine the oscillator frequency. Use a capacitor in the range 100 pF to 1 000 pF and a resistor in the range 3 kW to 33 kW . Use an oscillator frequency in the range 20 kHz to 1 MHz.
18 IN +3: I
Noninverting input to the error amplifier 3.
19 IN -3: I
Inverting input to the error amplifier 3.
20 FB3: O
Output from the error amplifier 3. This circuit can provide a source current of -31 mA or a sink current of 0.5 mA (minimum). n Terminal Equivalent Circuits (continued) 0.2 V V CC Latch S R Q
100 W 100 W
0.5 mA OSC PWM3
Voltage Regulators AN8049SH Pin No. Equivalent circuit Description I/O
21 IN -2: I
Inverting input to the error amplifier 2.
22 FB2: O
Output from the error amplifier 2. This circuit can provide a source current of -31 mA or a sink current of 0.5 mA (minimum).
23 IN -1: I
Inverting input to the error amplifier 1.
24 FB1: O
Output from the error amplifier 1. This circuit can provide a source current of -31 mA or a sink current of 0.5 mA (minimum). n Terminal Equivalent Circuits (continued) 1.26 V 1.5 kW 31 mA 0.5 mA min. 1.19 V OSC PWM2 1.26 V 1.5 kW 31 mA 1.19 V OSC PWM123 0.5 mA min.
AN8049SH Voltage Regulators n Usage Notes [1] Allowable power dissipation 1. Since the power dissipation (P) in this IC increases proportionally with the supply voltage, applications must be careful to operate so that the loss does not exceed the allowable power dissipation, PD , for the package. See the PD ¾ Ta curve. Reference formula: P = (VCC -V BEQ1 ) · ISO(OUT)1 · Du1+ (VCC -V BEQ2 ) · ISO(OUT)2 · Du2+V O(SAT)3 · IOUT3 · Du3+V CC · ICC < PD V BEQ1 : The voltage between the base and emitter of the channel 1 npn transistor ISO(OUT)1 : The OUT1 pin output source current (This is set by the resistor connected to the RB1 pin. When RB is 1 kW , ISO(OUT)1 will be 34 mA, maximum.) Du 1 : The output 1 on-duty V BEQ2 : The voltage between the base and emitter of the channel 2 npn transistor ISO(OUT)2 : The OUT2 pin output source current (This is set by the resistor connected to the RB2 pin. When RB is 1 kW , ISO(OUT)2 will be 34 mA, maximum.) Du 2 : The output 2 on-duty V O(SAT)3 : The OUT3 pin saturation voltage (0.5 V maximum when IOUT3 is 40 mA.) IOUT3 : The OUT3 pin current (This will be {VCC - VBEQ3 - VO(SAT)3 }/RO3 .) Du 3 : The output 3 on-duty ICC : The VCC pin current 2. If the IC is shorted to ground, shorted to VCC , or inserted incorrectly, either the device itself or peripheral components will be destroyed. [2] Allowable VCC ripple V CC ripple due to the switching transistor being turned on and off can cause this IC's U.V.L.O. circuit, which is biased by VCC , to operate incorrectly, and can cause the S.C.P. capacitor charging operation to fail to start when the output is shorted. The figure shows the allowable range for VCC ripple. Applications should reduce VCC ripple either by inserting a ripple filter in the VCC line or by inserting a capacitor between the IC GND and VCC pins and locating that capacitor as close to the IC as possible. Note that the allowable range shown here is the result of testing the IC independently, and that the allowable range may differ depending on the actual system of the power supply circuit. Also note that this allowable range is a design target, and is not guaranteed by testing of all samples. Allowable V CC ripple Ripple frequency (Hz) 10 M 1 M 100 k 10 k V CC ripple voltage VCC (AC) (V[p-p]) 012345678 Allowable range when VCC is 3 V . Allowable range when V CC is 10 V .
AN8049SH Voltage Regulators fOSC ¾ Maximum output duty (RT = 3 kW ) fOSC ¾ Maximum output duty (RT = 33 kW ) 1M100k10k fOSC (Hz) Du 1 , Du2 , Du3 (%) Du 1 , Du2 Du 3 n Application Notes (continued) [2] Main characteristics Timing capacitance ¾ Oscillator frequency DT1 and DT2 pin voltage ¾ Maximum on-duty DT3 pin voltage ¾ Maximum on-duty 10k 10p 1n 10n C T (F) fOUT (Hz)100k R T = 3 kW R T = 33 kW R T = 7.5 kW 100 V DT (V) Du (%) f = 190 kHz f = 1 MHz 100 V DT3 (V) Du 3 (%) f = 190 kHz f = 1 MHz fOSC ¾ Maximum output duty (RT = 7.5 kW ) 1M100k10k fOSC (Hz) Du 1 , Du2 , Du3 (%) Du 1 , Du2 Du 3 1M100k10k fOSC (Hz) Du 1 , Du2 , Du3 (%) Du 3 Du 1 Du 2
Voltage Regulators AN8049SH n Application Notes (continued) [2] Main characteristics (continued) R B ¾ ISO(OUT) R B ¾ ISI(OUT) -10 -20 -30 -40 -50 -60 -70 -80 100k10k1k100 R B (W ) ISO(OUT) (mA) V CC = 1.8 V 2.4 V 14 V 8 V 100 100k10k1k100 R B (W ) ISI(OUT) (mA) 1.8 V , 2.4 V 8 V V CC = 14 V
AN8049SH Voltage Regulators n Application Notes (continued) [3] Timing charts Output short 1.26 V V CC 0 V OSC FB OSC DT 1.67 V 1.26 V V CC pin voltage waveform S.C.P. pin voltage waveform CTL pin voltage waveform OUT1/2 pin voltage waveform Totem pole circuit output OUT3 pin voltage waveform Open-collector output
Voltage Regulators AN8049SH n Application Notes (continued) [4] Function descriptions (continued) This circuit protects the system against degradation or destruction due to incorrect control operation when the power supply voltage falls during power on or power off. The low input voltage malfunction prevention circuit detects the internal reference voltage that changes with the supply voltage level. While the supply voltage is rising, this circuit cuts off the output drive transistor until the 1) and the DT pins (pins 2, 3, and 4) at 0 V, and the OSC pin (pin 17) at about 1.2 V. 8. PWM comparators The PWM comparators control the on-period of the output pulse according to their input voltage. The PWM 1 and PWM 2 comparators reverse the logic of their inputs when adjusting the on-period of their respective output. The output transistors are turned on during periods when the OSC pin (pin 17) triangular waveform is lower than both of the corresponding FB pin (pins 20, 22, or 24) and the corresponding DT pin (pins 2, 3, or 4). The maximum duty is set to 86 % internally, but can be set to a value in the range 0% to 100% by inserting a resistor between the DT pin and ground, or the DT pin and V REF pin. (See the "[6] Setting the maximum duty" section later in this document.) The IC's soft start function operates to gradually increase the width of the output pulse on-period during startup if a capacitor is inserted between the DT pin and ground. See the "[7] Setting the soft start time" section later in this document. 9. Output 1 and output 2 blocks These output circuits have a totem pole structure. A constant-current source output with good line regulation can be set up freely by connecting current setting resistors to the RB pins (pins 10 and 11). See the "[2] Main characteristics" section earlier in this document for details on the R B vs. ISO(OUT) and RB vs. ISI(OUT) characteristics. 10. Output 3 block This output circuit has an open collector structure. An output current of up to 50 mA can be provided, and the output pin has a breakdown voltage of 14.2 V. 11. CTL block This block controls the on/off state of each channel. See the "[9] Sequential operation" section later in this document.
comparator continuously compares a 0.9 V reference voltage with the FB1, FB2, and FB3 error amplifier outputs. be in the conducting state, and the S.C.P. pin will be held at 0 V. SCP connected to the S.C.P. pin will start to charge. is turned off or the power supply is re-started by on/off control.
1.26 V = I
Figure 5. S.C.P. pin charging waveform Figure 6. Short-circuit protection circuit
Voltage Regulators AN8049SH n Application Notes (continued) [6] Setting the maximum duty The maximum duty is set to 86% internally to the IC. However, this setting can be changed to be any value in the range 0% to 100% by adding an external resistor. 1. To use a duty lower than the current duty (80% to 92%) Insert the resistor RDT between the DT pin and ground. Determine the DT pin voltage for the required duty from the provided DT pin voltage vs. maximum on-duty characteristics in the "[2] Main characteristics" section and determine the value of the external resistor RDT from formula A. Note that there is a sample-to-sample variation of -19% to +33% due to temperature characteristics and sample- to-sample variations of the internal resistors R1 and R2. (However, the direction of the sample-to-sample varia- tions is identical for R1 and R2.) Determine the size of the sample-to-sample variations in the DT pin voltage V DT from formula B, and estimate the size of the sample-to-sample variation in the duty from the provided DT pin voltage vs. maximum on-duty characteristics in the "[2] Main characteristics" section . V R 1+R 2/RDT ch.1, 2 ch.3 R1 45 k W 44 kW R2 55 k W 56 kW 2. To use a duty higher than the current duty (80% to 92%) Insert the resistor RDT between the DT pin and the VREF pin. Use formulas C and D to determine the value of the external resistor RDT and the size of the sample-to-sample variations in the same manner as in item 1 above. R DT = V DT V REF - ( 1 + 1 ) · V DT R 1 R1 R2 R DT = V REF -V DT ( 1 + 1 ) · V DT - VREF R 1 R 2 R 1 V REF 1.26 V DT R DT V REF 1.26 V DT R DT
AN8049SH Voltage Regulators n Application Notes (continued) [7] Setting the soft start time The soft start time is determined by the value of the capacitor connected between the DT pin and ground. Use the following formula to set the soft start time tD . tD = -R 2 · CDT · ln (1- VDT · R 1 )V REF - VDT R 2 ch.1, 2 ch.3 R1 45 k W 44 kW R2 55 k W 56 kW OSC pin waveform DT pin waveform V DT 0.2 V Soft start time, tD V REF 1.26 V DT C DT
to each other as shown in figure 7, the ICs will operate at the same frequency. Figure 7. Synchronous parallel operation
- The remote on/off state of each individual IC cannot be controlled independently.
temporarily to the full off-state and the DC-DC converter output voltage will fall.
- All ICs are shut down when an output shorted state occurs.
the OSC pin is held fixed at about 1.2 V. latched state. This behavior will also occur if the IC2 output falls first.
Delays can be provided in the startup times by inserting capacitors (CCTL ) between the CTL pins and ground. Figure 8. Sequential operation using external capacitors
Voltage Regulators AN8049SH n Application Notes (continued) [10] Notes on power supply printed circuit board design Careful attention must be paid to the following points when designing the printed circuit board layout to achieve low noise and high efficiency. 1. Use extremely wide lines for the ground lines, and isolate the IC ground from the power system ground. In particular, during light-load operation (when the on-duty is low) switching noise can enter the system at the lower limit of the sawtooth waveform causing the operating frequency to vary every period and resulting in unstable control. Take measures described as 1) and 2) below, and assure that switching noise does not appear on the sawtooth waveform. 1) Use a ground line separate from the power system ground for the capacitor and resistor connected to the OSC pin. 2) Lower the OSC pin impedance by either decreasing the value of the resistor R T or increasing the value of the capacitor CT. (See the figures below.) 2. Position input filter capacitors as close as possible to the VCC and ground pins. If switching noise cannot be suppressed even with exceptionally large capacitors, or if there are limitations on the size of capacitors that can be used, install an CR filter in the input to reduce switching noise. Problems may occur if switching noise enters the IC by any route. 3. Keep the length of the line between the OUT pin and the switching device as short as possible to provide a clean switching waveform to the switching device. 4. Use longer lines for the low-impedance side of the output voltage detection resistors. OSC 17 OUT1 12 V IN V OUT R T C T GND Common impedance OSC 17 OUT1 12 V IN V OUT R T C T GND (1) Use separate lines. (2) Modify the values of the capacitor and resistor. Lower limit voltage of the sawtooth wave during stable operation Small Large The frequency changes at each period. Noise is picked up and the IC switches from charge to discharge operation.
AN8049SH Voltage Regulators n Application Notes (continued) [11] Differences between this IC and the AN8049FHN The pin arrangements differ. The AN8049FHN is a alternative package version of this IC. CTL1 Off V REF RB2 RB1 OUT1 CTL2 CTL3 DT1 DT2 DT3 S.C.P. IN+3 OSC V CC OUT3 GND OUT2 IN-3 FB3 IN-2 FB2 IN-1 FB1 IN-2 FB3 IN-3 IN+3 OSC V CC OUT3 DT2 1 DT1 CTL3 CTL2 CTL1 Off V REF RB1 OUT1 OUT2 GND RB28 FB2 IN-1 FB1 22 S.C.P. 23 DT3 24 AN8049SH AN8049FHN
Voltage Regulators AN8049SH n Application Notes (continued) [12] Error amplifier frequency characteristics 1. Error amplifiers 1 and 2 (Test circuit) 180 135 -45 Phase (°) Frequency (Hz) 100M100k 1M 10M10k1k -10 -20 Gain (dB) Amp.1 V REF 1.26 V 100 kW 100 kW 1 kW10 mF FB1 V OUT 2.3 V V IN 4 mV[P-P] IN-1 2. Error amplifier 3 (Test circuit) -45 -135 -180 -90 -225 Phase (°) Frequency (Hz) 100M100k 1M 10M10k1k -10 -20 Gain (dB)Amp.3 1 kW 100 kW 1 kW 1 kW 10 mF 10 mF FB3 V OUT 1 V V IN 4 mV[P-P] IN-3 IN+3
AN8049SH Voltage Regulators n Application Circuit Example IN-3 FB3 IN-2 FB2 IN-1 FB1 IN+3 OSC V CC OUT3 GND Input OUT2 CTL2 CTL3 DT1 DT2 DT3 S.C.P. CTL1 Off V REF RB2 RB1 OUT1 Step-down V OUT1 3.3 V 300 mA Step-up V OUT2 13.3 V 300 mA Inverting V OUT3 -15 V 10 mA V REF 10 kW 10 kW 2.2 kW 150 kW 125.1 kW 13 kW 12 kW 14 kW 23 kW 100 pF 0.033 mF 10 mF 10 mF 10 mF 10 mF 100 pF 100 W 1 kW 7.5 kW 9.1 kW 1 kW On/Off 0.12 mF 0.12 mF 0.12 mF 0.12 mF 0.01 mF 0.01 mF0.01 mF 0.12 mF 470 pF