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| FUJITSU SEMICONDUCTOR DATA SHEET DS04-27208-1E ASSP BIPOLAR Switching Regulator Controller (4 Channels plus High-Precision, High-Frequency Capabilities) MB3785A s DESCRIPTION The MB3785A is a PWM-based 4-channel switching regulator controller featuring high-precision, high-frequency capabilities. All of the four channels of circuits allow their outputs to be set in three modes: step-down, step-up, and inverted. The third and fourth channels are suited for DC motor speed control. The triangular-wave oscillation circuit accepts a ceramic resonator, in addition to the standard method of oscillation using an RC network. s FEATURES * * * * Wide range of operating power supply voltages: 4.5 V to 18 V Low current consumption: 6 mA [TYP] when operating10 A or less during standby Built-in high-precision reference voltage generator: 2.50 V1% Oscillation circuit - Capable of high-frequency oscillation: 100 kHz to 1 MHz - Also accepts a ceramic resonator. * Wide input range of error amplifier: -0.2 V to VCC-1.8 V * Built-in timer/latch-actuated short-circuiting detection circuit (Continued) s PACKAGE 48-pin, Plastic LQFP (FPT-48P-M05) MB3785A (Continued) * Output circuit - The drive output for PNP transistors is the totem-pole type allowing the on-current and off-current values to be set independently. * Adjustable dead time over the entire duty ratio range * Built-in standby and output control functions * High-density mounting possible: 48-pin LQFP package s PIN ASSIGNMENT (TOP VIEW) OUT1 OUT2 OUT3 VCC2 OUT4 GND VE2 VE3 VE1 VE4 38 Cb1 48 Ca1 Cb2 Ca2 DTC1 FB1 -IN1 (E) +IN1 (E) -IN1 (C) DTC2 FB2 -IN2 (E) +IN2 (E) 1 2 3 4 5 6 7 8 9 10 11 12 13 47 46 45 44 43 42 41 40 39 37 36 35 34 33 32 31 30 29 28 27 26 25 Ca4 Cb3 Ca3 DTC4 FB4 -IN4 (E) +IN4 (E) -IN4 (C) DTC3 FB3 -IN3 (E) +IN3 (E) 14 15 16 17 18 19 20 21 22 23 24 -IN2 (C) (FPT-48P-M05) Each alphabet in parentheses following the pin symbol indicates the input pin of the next circuit. (C) denotes a comparator. (E) denotes an error amplifier. 2 -IN3 (C) CTL1 OSCIN OSCOUT CTL2 CTL3 RT CT VCC1 VREF SCP Cb4 MB3785A s PIN DESCRIPTION Pin No. 1 48 7 6 CH1 5 8 4 47 46 3 2 12 11 CH2 10 13 9 43 44 34 35 25 26 CH3 27 24 28 41 40 36 37 CH4 30 31 32 29 Symbol Ca1 Cb1 +IN1(E) -IN1(E) FB1 -IN1(C) DTC1 VE1 OUT1 Ca2 Cb2 +IN2(E) -IN2(E) FB2 -IN2(C) DTC2 VE2 OUT2 Ca3 Cb3 +IN3(E) -IN3(E) FB3 -IN3(C) DTC3 VE3 OUT3 Ca4 Cb4 +IN4(E) -IN4(E) FB4 -IN4(C) I/O -- -- I I O I I I O -- -- I I O I I I O -- -- I I O I I I O -- -- I I O I Description CH1 output transistor OFF-current setting pin. Insert a capacitor between the Ca1 and the Cb1 pins, then set the output transistor OFF-current. CH1 error amp non-inverted input pin. CH1 error amp inverted input pin. CH1 error amp output pin. CH1 comparator inverted input pin. CH1 dead time control pin. CH1 output current setting pin. CH1 totem-pole output pin. CH2 output transistor OFF-current setting pin. Insert a capacitor between the Ca2 and the Cb2 pins, then set the output transistor OFF-current. CH2 error amp non-inverted input pin. CH2 error amp inverted input pin. CH2 error amp output pin. CH2 comparator inverted input pin. CH2 dead time control pin. CH2 output current setting pin. CH2 totem-pole output pin. CH3 output transistor OFF-current setting pin. Insert a capacitor between the Ca3 and the Cb3 pins, then set the output transistor OFF-current. CH3 error amp non-inverted input pin. CH3 error amp inverted input pin. CH3 error amp output pin. CH3 comparator inverted input pin. CH3 dead time control pin. CH3 output current setting pin. CH3 totem-pole output pin. CH4 output transistor OFF-current setting pin. Insert a capacitor between the Ca4 and the Cb4 pins, then set the output transistor OFF-current. CH4 error amp non-inverted input pin. CH4 error inverted input pin. CH4 error amp output pin. CH4 comparator inverted input pin. (Continued) 3 MB3785A (Continued) Pin No. 33 CH4 38 39 Triangular-Wave Oscillator Circuit 14 15 16 17 18 45 42 19 23 20 Symbol DTC4 VE4 OUT4 OSCIN OSCOUT RT CT VCC1 VCC2 GND VREF SCP CTL1 I/O I I O -- -- -- -- -- -- -- O -- I This pin connects a ceramic resonator. CH4 dead time control pin. CH4 output current setting pin. CH4 totem-pole output pin. Description This pin connects to a resistor for setting the triangular-wave frequency. This pin connects to a capacitor for setting the triangular-wave frequency. Power supply pin for the reference power supply control circuit. Power supply pin for the output circuit. GND pin. Reference voltage output pin. This pin connects to a capacitor for the short-circuit protection circuit. Power supply circuit and first-channel control pin. When this pin is High, the power supply circuit and first channel are in active state. When this pin is Low, the power supply circuit and first channel are in standby state. Control Circuit Power Supply Circuitt 21 CTL2 I Second-channel control pin. While the CTL1 pin is High When this pin is High, the second channel is in active state. When this pin is Low, the second channel is in the inactive state. 22 CTL3 I Third and fourth-channel control pin. While the CTL1 pin is High When this pin is High, the third and fourth channels are in active state. When this pin is Low, the third and fourth channels are in the inactive state. 4 MB3785A s BLOCK DIAGRAM Ca1 CH 1 Error Amp 1 1 48 Cb1 +IN1 (E) -IN1 (E) FB1 -IN1 (C) DTC1 7 6 5 + - VREF PWM comparator 1 + Comparator 1 - - + VREF OFF Current Setting 45 VCC2 - DTC 2V Comparator 1 46 OUT1 + - 8 4 2.5 V CH 2 Error Amp 2 47 VE1 3 2 +IN2 (E) -IN2 (E) FB2 -IN2 (C) DTC2 12 11 10 + - VREF PWM comparator 2 Ca2 Cb2 + Comparator 2 - - + VREF OFF Current Setting - DTC Comparator 2 2V 44 OUT2 + 13 9 - 2.5 V CH 3 Error Amp 3 43 VE2 34 33 Ca3 +IN3 (E) -IN3 (E) FB3 -IN3 (C) DTC3 25 26 27 + - Comparator 3 0.6 V PWM comparator 3 Cb3 OFF Current Setting + + - 100 40 OUT3 + - 24 28 2.5 V CH 4 Error Amp 4 41 VE3 Ca4 36 37 +IN4 (E) -IN4 (E) FB4 -IN4 (C) DTC4 30 31 32 + - Comparator 4 0.6 V PWM comparator 4 + + - 100 OFF Current Setting Cb4 39 OUT4 + - 29 33 2.5 V 38 VE4 21 SCP Comparator - - - - + 2.1 V 22 CTL2 CTL3 SCP 23 1 A DTC Comparator 3 - - + 1.2 V -1.9 V -1.3 V 18 Ref. Power Supply Vol. Circuit & Channel Circuit Control VCC1 CTL1 VREF S R SR Latch Under Voltage Lock-out Protection Circuit Triangular-Wave Oscillator Circuit 20 2.5 V OSCIN 14 15 16 17 19 42 RT CT VREF GND OSCOUT Ceramic Resonator 5 MB3785A s FUNCTIONAL DESCRIPTION 1. Switching Regulator Function (1) Reference voltage circuit The reference voltage circuit generates a temperature-compensated reference voltage ( 2.50 V) using the voltage supplied from the power supply terminal (pin 18). This voltage is used as the operating power supply for the internal circuits of the IC. The reference voltage can also be supplied to an external device from the VREF terminal (pin 19). (2) Triangular-wave oscillator circuit By connecting a timing capacitor and a resistor to the CT (pin 17) and the RT (pin 16) terminals, it is possible to generate any desired triangular oscillation waveform. The oscillation can also be obtained by using a ceramic resonator connected to pins 14 and 15. This waveform has an amplitude of 1.3 V to 1.9 V and is input to the internal PWM comparator of the IC. At the same time, it can also be supplied to an external device from the CT terminal (pin 17). (3) Error amplifier This amplifier detects the output voltage of the switching regulator and outputs a PWM control signal accordingly. It has a wide common-mode input voltage range from -0.2 V to VCC -1.8 V and allows easy setting from an external power supply, making the system suitable for DC motor speed control. By connecting a feedback resistor and capacitor from the error amplifier output pin to the inverted input pin, you can form any desired loop gain, for stable phase compensation. (4) PWM comparator * CH1 & CH2 The PWM comparators in these channels are a voltage comparator with two inverted input and one non-inverted input, that is, a voltage-pulse width converter to control the output pulse on-time according to the input voltage. It turns on the output transistor when the triangular wave from the oscillator is higher than both the error amplifier output and the DTC-pin voltages. * CH3 & CH4 The PWM comparators in these channels are a voltage comparator with one inverted input and two non-inverted inputs, that is, a voltage-pulse width converter to control the output pulse on-time according to the input voltage. It turns on the output transistor when the triangular wave from the oscillator is lower than both the error amplifier output and the DTC-pin voltages. These four channels can be provided with a soft start function by using the DTC pin. (5) Output circuit The output circuit is comprised of a totem-pole configuration and can drive a PNP transistor (30 mA max.) 6 MB3785A 2. Channel Control Function The MB3785A allows the four channels of power supply circuits to be controlled independently. Set the voltage levels on the CTL1 (pin 20), CTL2 (pin 21), and CTL3 (pin 22) terminals to turn the circuit of each channel "ON" or "OFF", as listed below. Table 1 Channel by Channel On/Off Setting Conditions. CTL pin voltage level CTL1 CTL2 H H L L X CTL3 H L H L Standby state* ON OFF Power supply circuit On/Off state of channel First channel Second channel 3rd and 4th channels ON ON OFF ON OFF * : The power supply current value during standby is 10 A or less. 3. Protective Functions (1) Timer/latch-actuated short-circuiting protection circuit The SCP comparator checks the output voltage of each comparator which is used to detect the short-circuiting of output. When any of these comparators have an output voltage greater than or equal to 2.1 V, the timer circuit is activated and a protection enable capacitor externally fitted to the SCP terminal (pin 23) begins to charge. If the comparator's output voltage is not restored to normal voltage level by the time the capacitor voltage has risen to the base-emitter junction voltage of the transistor, i.e., VBE ( 0.65 V), the latch circuit is activated to turn off the output transistor while at the same time setting the duty (OFF) = 100 %. When actuated, this protection circuit can be reset by turning on the power supply again. (2) Under voltage lockout protection circuit A transient state at power-on or a momentary drop of the power supply voltage causes the control IC to malfunction, resulting in system breakdown or deterioration. By detecting the internal reference voltage with respect to the power supply voltage, this protection circuit resets the latch circuit to turn off the output transistor and set the duty (OFF) = 100 %, while at the same time holding the SCP terminal (pin 23) at the "L". The reset is cleared when the power supply voltage becomes greater than or equal to the threshold voltage level of this protection circuit. 7 MB3785A s ABSOLUTE MAXIMUM RAGINGS (See WARNING) (Ta = +25C) Parameter Power supply voltage Control input voltage Power dissipation Operating ambient temperature Storage temperature Symbol VCC VICTL PD TOP Tstg Conditions -- -- Ta +25C -- -- Rating 20 20 550* -30 to 85 -55 to 125 Unit V V mW C C * : The packages are mounted on the epoxy board (4 cm x 4 cm). WARNING: Permanent device damage may occur if the above Absolute Maximum Ratings are exceeded. Functional operation should be restricted to the conditions as detailed in the operational sections of this data sheet. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. s RECOMMENDED OPERATING CONDITIONS (Ta = +25C) Parameter Power supply voltage* Error amp. input voltage Comparator input voltage Control input voltage Output current Timing capacitance Timing resistance Oscillation frequency Operating ambient temperature Symbol VCC VI VI VICTL IO CT RT fOSC TOP Conditions -- -- -- -- -- -- -- -- -- Value Min. 4.5 -0.2 -0.2 -0.2 3.0 68 5.1 100 -30 Typ. 6.0 -- -- -- -- -- -- 500 25 Max. 18 VCC -0.8 VCC 18 30 1500 100 1000 85 Unit V V V V mA pF k kHz C * : The minimum value of the recommended supply voltage is 3.6 V except when the device operates with constant output sink current. 8 MB3785A s ELECTRICAL CHARACTERISTICS (VCC = +6 V, Ta = +25C) Parameter Reference voltage Reference voltage block Rate of changed in output voltage vs. Temperature Input stability Load stability Sort-circuit output current Under voltage lockout protection circuit (U.V.L.O) Threshold voltage Hysteresis width Reset voltage (VCC) Input threshold voltage Input bias current Input voltage range Input offset voltage Input bias current Common mode input voltage range Threshold voltage Input standby voltage Input latch voltage Input source current Oscillation frequency Frequency stability (VCC) Symbol VREF VREF /VREF Line Load IOS VtH VtL VHYS VR Vth IIB VI VIO IIB VICM VtPC VSTB VI Ilbpc fOSC f/fdv f/fdT VI = 0 V -- -- -- -- -- CT = 300 pF, RT = 6.2 k VCC = 3.6 V to 18 V VI = 0 V -- -- Conditions IOR = -1 mA Ta = -30C to +85C VCC = 3.6 V to 18 V IOR = -0.1 mA to -1 mA VREF = 2 V -- -- -- -- -- Value Min. 2.475 -2 -10 -10 -25 -- -- 80 1.5 2.45 -200 -0.2 0.58 -200 -0.2 0.60 -- -- -1.4 450 -- Typ. 2.500 0.2 -2 -3 -8 2.72 2.60 120 1.9 2.50 -100 -- 0.65 -100 -- 0.65 50 50 -1.0 500 1 Max. 2.525 2 10 10 -3 -- -- -- -- 2.55 -- VCC 0.72 -- VCC-1.8 0.70 100 100 -0.6 550 -- Unit V % mV mV mA V V mV V V nA V V nA V V mV mV A kHz % Short-circuit detection comparator Short circuit detection block Triangular waveform oscillator block 3 CH/4 CH 1 CH/2 CH Frequency stability (Ta) Ta = -30C to +85C -4 -- 4 % (Continued) 9 MB3785A (Continued) (VCC = +6 V, Ta = +25C) Parameter Input offset voltage Error amplifier Input bias current Common mode input voltage range Voltage gain Frequency bandwidth 1 CH/2 CH dead time control circuit Input threshold voltage Input bias current Latch mode source current Latch input voltage Input threshold voltage Input bias current Latch mode source current Latch input voltage Threshold voltage Input current Source current Output block Sink current Output leakage current Standby current Supply current when output off Symbol VIO IIB VICM AV BW Vt0 Vt100 IIbdt IIdt VIdt Vt0 Vt100 IIbdt IIdt VIdt Vth IIH IIL IO IO ILO ICC0 ICC RE = 82 VO = 18 V -- -- VCTL = 5 V VCTL = 0 V -- AV = 0 dB Duty cycle = 0 % Duty cycle = 100 % Vdt = 2.3 V Vdt = 1.5 V Idt = -40 A Duty cycle = 0 % Duty cycle = 100 % Vdt = 2.3 V Vdt = 1.5 V Idt = +40 A -- Conditions VFB = 1.6 V VFB = 1.6 V -- -- Value Min. -10 -200 -0.2 60 -- -- 1.05 -- -- VREF- 0.3 1.05 -- -- 80 -- 0.7 -- -10 -- 18 -- -- -- Typ. -- -100 -- 100 800 1.9 1.3 0.1 -500 2.4 1.3 1.9 0.1 500 0.2 1.4 100 -- -40 30 -- 0 6 Max. 10 -- VCC-1.8 -- -- 2.25 -- 0.5 -80 -- -- 2.25 0.5 -- 0.3 2.1 200 10 -- 42 20 10 8.6 Unit mV nA V dB kHz V V A A V V V A A V V A A mA mA A A mA 10 General Channel control block 3 CH/4 CH dead time control circuit MB3785A s TYPICAL CHARACTERISTIC CURVES 1. Supply current vs. Supply voltage 2. Reference voltage vs. Supply voltage 10 Supply current ICC (mA) Ta = +25C Reference voltage VREF (V) 5 4 3 Ta = +25C 8 6 CTL1, 2 = 6 V, CTL1, 2, 3 = 6 V CTL1 = 6 V 4 2 0 2 1 0 0 4 8 12 16 20 0 4 8 12 16 20 Supply voltage VCC (V) Supply voltage VCC (V) 3. Reference voltage and Output current setting pin voltage vs. Supply voltage 5 Reference voltage VREF (V) 4. Reference voltage vs. Ambient temperature Voltage on Output Current -- Setting Pin VE (V) 2.56 2.54 Reference voltage VREF (V) Ta = +25C 5 4 4 VCC = 6 V VCTL1, 2,3 = 6 V IOR = -1 mA VREF 2.52 2.50 2.48 2.46 2.44 -60 -40 -20 0 20 40 60 80 100 3 2 1 3 2 1 VE 0 1 2 3 4 5 Supply voltage VCC (V) Ambient temperature Ta (C) 5. Reference voltage vs. Control voltage VCC = 6 V Ta = +25C Control current ICTL1 (A) 6. Control current vs. Control voltage VCC = 6 V Ta = +25C 3.0 Reference voltage VREF (V) 500 400 300 200 100 0 2.8 2.6 2.4 2.2 2.0 0 1 2 3 4 5 0 4 8 12 16 20 Control voltage VCTL1 (V) Control voltage VCTL1 (V) (Continued) 11 MB3785A (Continued) 7. Triangular wave maximum amplitude voltage vs. Timing capacitance 2.4 Triangular - wave maximum amplitude voltage VMAX (V) Triangular wave frequency fOSC (Hz) 8. Triangular wave frequency vs. Timing resistance 5M VCC = 6 V Ta = +25C 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0 50 102 5 x 102 103 VCC = 6 V RT = 10 k Ta = +25C 1M 500 K 100 K 50 K CT = 68 pF 10 K 5K CT = 15000 pF CT = 150 pF CT = 300 pF 5 x 103104 5 x 104105 Timing capacitance CT (pF) 1K CT = 1500 pF 5 K10 K 50 K100 K 500 K 1 M 9. Triangular wave cycle vs. Timing capacitance 100 50 Triangular wave cycle TOSC (sec) Timing resistance RT () VCC = 6 V RT = 10 k Ta = +25C 10 5 Duty Dtr (%) 10. Duty vs. Triangular wave frequency 100 CH 1 80 60 40 20 0 VCC = 6 V VDT = 1.60 V Ta = +25C 1 0.5 0.2 10 102 5 x 102 103 5 x 103 104 5 x 104 5 K 10 K 50 K 100 K 500 K 1 M Timing capacitance CT (pF) Triangular wave frequency (Hz) 11. Rate of change in triangular wave frequency vs. Ambient temperature (Not using ceramic resonator) Rate of change in triangular Wave frequency (%) 12. Rate of change in triangular wave frequency vs. Ambient temperature (Using ceramic resonator) 10 Rate of change in triangular Wave frequency (%) 10 5 VCC = 6 V fOSC = 460 kHz (RT = 6.8 k, CT = 280 pF) VCC = 6 V fOSC = 450 kHz (RT = 8.5 k, CT = 250 pF) 5 0 0 -5 -5 -10 -40 -20 0 20 40 60 80 100 -10 Ambient temperature Ta (C) -40 -20 0 20 40 60 80 100 Ambient temperature Ta (C) (Continued) 12 MB3785A (Continued) 13. Gain vs. Frequency and Phase vs. Frequency Ta = +25C 14. Error amp maximum output voltage vs. Frequency Error amp maximum output voltage amplitude (V) 40 20 0 -20 -40 1K 10 K 100 K Frequency f (Hz) 180 90 0 3.0 CH 1 2.0 VCC = 6V Ta = +25C Phase (deg) Gain AV (dB) A -90 -180 1M 10 M 1.0 0 100 500 1 K 5 K 10 K 50 K 100 K 500 K 1 M Triangular wave frequency fOSC (Hz) [Measuring Circuit] 2.5 V 2.5 V 4.7 k 240 k 4.7 k - 10 F -+ 4.7 k OUT + 4.7 k Error amp IN 15. Power dissipation vs. Ambient temperature 1000 Power dissipation Pd (mW) 800 600 550 400 200 0 -30 -20 LQFP 0 20 40 60 80 100 Ambient temperature Ta (C) 13 MB3785A s METHODS OF SETTING THE OUTPUT VOLTAGE 1. Method of Connecting Channels 1 and 2: When Output Voltage (VO) is Positive VREF VOUT+ R R1 + - VO+ = - VREF 2 x R2 (R1 + R2) R R2 RNF 2. Method of Connecting Channels 1 and 2: When Output Voltage (VO) is Negative VREF VO- = - VREF 2 x R1 (R1 + R2) + VREF R R1 + - R R2 RNF VOUT- 14 MB3785A 3. Method of Connecting Channels 3 and 4: When Output Voltage (VO) is Positive VREF VOUT R R1 + - VO+ = VREF 2 x R2 (R1 + R2) R R2 RNF 4. Method of Connecting Channels 3 and 4: When Output Voltage (VO) is Negative VREF VO- = - VREF 2 x R1 (R1 + R2) + VREF R R1 + - R R2 RNF VOUT- 15 MB3785A s METHOD OF SETTING THE OUTPUT CURRENT The output circuit is comprised of a totem-pole configuration. Its output current waveform is such that the ON-current value is set by constant current and the OFF-current value is set by a time constant as shown in Figure 2. These output currents are set using the equations below. * ON-current = 2.5/RE [A] (Voltage on output current-setting pin VE = 2.5 V) * OFF-current time constant = proportional to the value of CB Figure 1. CH1 to CH4 Output Circuit Drive transistor CB Figure 2. Output Current Waveform ON-current OFF-current OFF-current setting block Output current 0 OFF-current ON-current RE VE t Figure 3. Voltage and Current Waveforms on Output Pin (CH1) VCC = 10 V Figure 4. Measuring Circuit Diagram 10 VO (V) 1000 pF VCC 0 40 1 48 45 8 pin 22 H VO 10 F 8.2 k 2.7 k 7 pin (5 V) IO 20 MB3785A 46 IO (mA) 570 pF 47 0 -20 -40 0 0.4 0.8 t (S) 1.2 1.6 2.0 82 16 MB3785A s METHOD OF SETTING TIME CONSTANT FOR TIMER/LATCH-ACTUATED SHORTCIRCUTING PROTECTION CIRCUIT Figure 5 schematically shows the protection latch circuit. The outputs from the output-shorting detection comparators 1 to 4 are respectively connected to the inverted inputs of the SCP comparator. These inputs are always compared with the reference voltage of approximately 2.1 V which is fed to the non-inverted input of the SCP comparator. While the switching regulator load conditions are stable, there are no changes in the outputs of the comparators 1 to 4 so that short-circuit protection control keeps equilibrium state. At this time, the voltage on the SCP terminal (pin 23) is held at approximately 50 mV. When load conditions change rapidly due to a short-circuiting of load, for example, the output voltage of the comparator for the relevant channel goes "H" (2.1 V or more). Consequently, the SCP comparator outputs a "L", causing the transistor Q1 to turn off, and the short-circuit protection capacitor CPE (externally fitted to the SCP terminal) begins to charge. VPE = 50 mV + tPE x 10-6/CPE 0.65 = 50 mV + tPE x 10-6/CPE CPE = tPE/0.6 (sec) When the external capacitor CPE is charged to approximately 0.65 V, the SR latch is set and the output drive transistor is turned off. Simultaneously, the dead time is extended to 100% and the output voltage on the SCP terminal (pin 23) is held "L". As a result, the S-R latch input is closed and CPE is discharged. Figure 5. Protection Latch Circuit 2.5 V 1 A Comparator 1 Comparator 2 Comparator 3 Comparator 4 - - - - + Q2 23 S R OUT PWM comparator Q1 Latch CPE U.V.L.O 2.1 V 17 MB3785A s TREATMENT WHEN NOT USING SCP When you do not use the timer/latch-actuated short-circuiting protection circuit, connect the SCP terminal (pin 23) to GND with the shortest distance possible. Also, connect the comparator's input terminal for each channel to the VCC1 terminal (pin 18). Figure 6. Treatment When Not Using SCP 18 VCC1 8 -IN1 (C) 13 -IN2 (C) 24 -IN3 (C) 29 -IN4 (C) 23 18 MB3785A s METHOD OF SETTING THE TRIANGULAR-WAVE OSCILLATOR CIRCUIT 1. When Not Using Ceramic Resonator Connect the OSCIN terminal (pin 14) to GND and leave the OSCOUT terminal (pin 15) open. This makes it possible to set the oscillation frequency with only CT and RT. Figure 7. When Not Using Ceramic Resonator OSCIN 14 OSCOUT 15 RT 16 RT CT 17 CT Open 2. When Using Ceramic Resonator By connecting a ceramic resonator between OSCIN and OSCOUT as shown below, you can set the oscillation frequency. In this case, too, CT and RT are required. Determine the values of CT and RT so that the oscillation frequency of this RC network is about 5-10% lower than that of the ceramic resonator. Figure 8. When Using Ceramic Resonator OSCIN 14 Ceramic resonator C1 OSCOUT 15 RT 16 RT CT 17 CT C2 19 MB3785A * Crystal Resonator Turn-on Characteristic 2.0 VCT (V) 1.5 1.0 0 1 2 3 t (msec) 4 5 * Ceramic Resonator Turn-on Characteristic 2.0 VCT (V) 1.5 1.0 0 1 2 3 t (msec) 4 5 20 MB3785A s METHOD OF SETTING THE DEAD TIME AND SOFT START 1. Dead Time When the device is set for step-up inverted output based on the flyback method, the output transistor is fixed to a full-on state (ON-duty = 100 %) at power switch-on. To prevent this problem, you may determine the voltages on the DTC terminals (pins 4, 9, 28, and 33) from the VREF voltage so you can easily set the output transistor's dead time (maximum ON-duty) independently for each channel as shown below. (1) CH1 and CH2 Channels When the voltage on the DTC terminals (pins 4 and 9) is higher than the triangular-wave output voltage from the oscillator, the output transistor turns off. The dead time calculation formula assuming that triangular-wave amplitude 0.6 V and triangular-wave minimum voltage 1.3 V is given below. Duty (OFF) = Vdt - 1.3 0.6 x 100 [%], Vdt = R2 R1 + R2 x VREF When you do not use these DTC terminals, connect them to GND. Figure 9. When Using DTC to Set Dead Time Figure 10. When Not Using DTC 19 R1 VREF DTC1 (DTC2) Vdt R2 DTC1 (DTC2) (2) CH3 and CH4 Channels When the voltage on the DTC terminals (pins 28 and 33) is lower than the triangular-wave output voltage from the oscillator, the output transistor turns off. The dead time calculation formula assuming that traingular-wave amplitude 0.6 V and triangular-wave maximum voltage 1.9 V is given below. Duty (OFF) 1.9 -Vdt 0.6 x 100 [%], Vdt = R2 R1 + R2 x VREF When you do not use these DTC terminals, connect them to VREF. 21 MB3785A Figure 11. When Using DTC to Set Dead Time Figure 12. When Not Using DTC 19 R1 VREF 19 VREF DTC3 (DTC4) Vdt R2 DTC3 (DTC4) 2. Soft Start To prevent inrush current at power switch-on, the device can be set for soft start by using the DTC terminals (pins 4, 9, 28, and 33). The diagrams below show how to set. Figure 13. Setting Soft Start for CH1 and CH2 Figure 14. Setting Soft Start for CH3 and CH4 19 Cdt Rdt VREF Rdt DTC1 (DTC2) Cdt 19 VREF DTC3 (DTC4) 22 MB3785A It is also possible to set soft start simultaneously with the dead time by configuring the DTC terminals as shown below. Figure 15. Setting Dead Time and Soft Start for CH1 and CH2 Figure 16. Setting Dead Time and Soft Start for CH3 and CH4 19 Cdt R1 VREF R1 DTC1 (DTC2) 19 VREF DTC3 (DTC4) Cdt R2 R2 23 MB3785A s EQUIVALENT SERIES RESISTOR AND STABILITY OF SMOOTHING CAPACITOR The equivalent series resistance (ESR) of a smoothing capacitor in a DC/DC converter greatly affects the phase characteristics of the loop depending on its value. System stability is improved by ESR because it causes the phase to lead that of the ideal capacitor in high-frequency regions. (See Figures 17 and 19.) Conversely, if a low-ESR smoothing capacitor is used, system stability deteriorates. Therefore, use of a low-ESR semiconductor electrolytic capacitors (OS - CON) or tantalum capacitors calls for careful attention. Figure 17. Basic Circuit of Stepdown DC/DC Converter Tr L RC VIN D C RL Figure 18. Gain-Frequency Characteristic Figure 19. Phase-Frequency Characteristic 20 0 0 Phase (deg) Gain (dB) (2) -90 -20 (2) -40 (1) : RC = 0 (2) : RC = 31 m 10 100 1k Frequency f (Hz) (1) : RC = 0 (1) (1) (2) : RC = 31 m -180 -60 10 k 100 k 10 100 1k Frequency f (Hz) 10 k 100 k 24 MB3785A (Reference Data) The phase margin is halved by changing the smoothing capacitor from an aluminum electrolytic capacitor (RC = 1.0 ) to a small-ESR semiconductor electrolytic capacitor (OS - CON; RC = 0.2 ). (See Figure 21 and 22.) Figure 20. DC/DC Converter AV- Characteristic Measuring Circuit VOUT VO+ CNF AV-o characteristic between this interval -IN + FB - +IN R1 R2 VIN VREF/2 Error amp Figure 21. Gain-Frequency Characteristic Gain - frequency and phase frequency characteristics of Al electrolytic capacitor (DC/DC converter +5 V output) 60 40 Gain (dB) AV Phase (deg) 20 0 -20 -40 62 VCC = 10 V RL = 25 CP = 0.1 F 180 90 0 -90 VO+ + Al electrolytic capacitor 220 F (16 V) - RC 1.0 : FOSC = 1 kHz GND 10 100 1k Frequency f (Hz) 10 k -180 100 k Figure 22. Phase-Frequency Characteristic Gain - frequency and phase frequency characteristics of OS - CON (DC/DC converter +5 V output) 60 40 Gain (dB) 20 0 -20 -40 27 AV VCC = 10 V RL = 25 CP = 0.1 F 180 VO+ 90 0 -90 -180 100 k Phase (deg) + OS - CON 22 F (16 V) - RC 0.2 : fOSC = 1 kHz GND 10 100 1k Frequency f (Hz) 10 k 25 MB3785A s EXAMPLE OF APPLICATION CIRCUIT VCC 33 F 1000 pF 1 48 VCC 10 H 33 F 22 H 10 F B 5V 8.2 k 2.7 k A 4.7 k 150 k 4.7 k +IN -IN FB RFB 7 6 5 45 CHI 46 OUT 1000 pF 10 mA B 33 k DTC 8 47 4 3 250 1000 pF A 1 F 27 k 2 +IN -IN FB 12 11 10 RFB 24 V C 4.7 k 150 k 4.7 k D 15 V CH2 44 OUT 1000 pF 10 mA 15 F 20 k 1.8 k D 13 27 k DTC 43 9 34 35 +IN 25 26 27 RFB 250 1000 pF Motor Control Signal 1 F 33 k C F 22 H 10 F DC motor E 150 k 8.2 k 2.7 k -IN FB CH3 40 OUT 1000 pF 10 mA F DTC 10 k Motor Control Signal 24 41 28 36 37 +IN 30 31 32 RFB 250 1000 pF E H 22 H 10 F DC motor G 150 k -IN FB 8.2 k 2.7 k CH4 39 OUT 1000 pF 10 mA H DTC 10 k 29 38 33 250 G VCC VREF 19 GND SCP 0.1 F 42 23 14 15 16 RT CT 6.2 k Ceramic Resonator Output Control Signals 17 300 pF 20 CTL1 21 CTL2 22 CTL3 18 26 MB3785A s PRECAUTIONS ON USING THE DEVICE 1. Do not input voltages greater than the maximum rating. Inputting voltages greater than the maximum rating may damage the device. 2. Always use the device under recommended operating conditions. If a voltage greater than the maximum value is input to the device, its electrical characteristics may not be guaranteed. Similarly, inputting a voltage below the minimum value may cause device operation to become unstable. 3. For grounding the printed circuit board, use as wide ground lines as possible to prevent high-frequency noise. Because the device uses high frequencies, it tends to generate high-frequency noise. 4. Take the following measures for protection against static charge: * For containing semiconductor devices, use an antistatic or conductive container. * When storing or transporting device-mounted circuit boards, use a conductive bag or container. * Ground the workbenches, tools, and measuring equipment to earth. * Make sure that operators wear wrist straps or other appropriate fittings grounded to earth via a resistance of 250 k to 1 M ohms placed in series between the human body and earth. s ORDERING INFORMATION Part number MB3785APFV Package 48-pin plastic LQFP (FPT-48P-M05) Remarks 27 MB3785A s PACKAGE DIMENSION 48-pin Plastic LQFP (FPT-48P-M05) 9.000.20(.354.008)SQ 7.000.10(.276.004)SQ 36 25 1.50 0.10 .059 .004 +0.20 +.008 (MOUNTING HEIGHT) 37 24 5.50 (.217) REF INDEX 8.00 (.315) NOM Details of "A" part 48 1 12 +0.08 0.03 +.003 .001 13 LEAD No. 0.500.08 (.0197.0031) 0.18 .007 "A" 0.127 0.02 .005 .001 +0.05 +.002 0.100.10 (STAND OFF) (.004.004) 0.500.20 (.020.008) 0.10(.004) 0 10 C 1995 FUJITSU LIMITED F48013S-2C-5 Dimensions in: mm (inches) 28 MB3785A FUJITSU LIMITED For further information please contact: Japan FUJITSU LIMITED Corporate Global Business Support Division Electronic Devices KAWASAKI PLANT, 4-1-1, Kamikodanaka Nakahara-ku, Kawasaki-shi Kanagawa 211-8588, Japan Tel: (044) 754-3763 Fax: (044) 754-3329 All Rights Reserved. The contents of this document are subject to change without notice. Customers are advised to consult with FUJITSU sales representatives before ordering. The information and circuit diagrams in this document presented as examples of semiconductor device applications, and are not intended to be incorporated in devices for actual use. Also, FUJITSU is unable to assume responsibility for infringement of any patent rights or other rights of third parties arising from the use of this information or circuit diagrams. FUJITSU semiconductor devices are intended for use in standard applications (computers, office automation and other office equipment, industrial, communications, and measurement equipment, personal or household devices, etc.). CAUTION: Customers considering the use of our products in special applications where failure or abnormal operation may directly affect human lives or cause physical injury or property damage, or where extremely high levels of reliability are demanded (such as aerospace systems, atomic energy controls, sea floor repeaters, vehicle operating controls, medical devices for life support, etc.) are requested to consult with FUJITSU sales representatives before such use. The company will not be responsible for damages arising from such use without prior approval. Any semiconductor devices have inherently a certain rate of failure. You must protect against injury, damage or loss from such failures by incorporating safety design measures into your facility and equipment such as redundancy, fire protection, and prevention of over-current levels and other abnormal operating conditions. If any products described in this document represent goods or technologies subject to certain restrictions on export under the Foreign Exchange and Foreign Trade Control Law of Japan, the prior authorization by Japanese government should be required for export of those products from Japan. http://www.fujitsu.co.jp/ North and South America FUJITSU MICROELECTRONICS, INC. Semiconductor Division 3545 North First Street San Jose, CA 95134-1804, USA Tel: (408) 922-9000 Fax: (408) 922-9179 Customer Response Center Mon. - Fri.: 7 am - 5 pm (PST) Tel: (800) 866-8608 Fax: (408) 922-9179 http://www.fujitsumicro.com/ Europe FUJITSU MIKROELEKTRONIK GmbH Am Siebenstein 6-10 D-63303 Dreieich-Buchschlag Germany Tel: (06103) 690-0 Fax: (06103) 690-122 http://www.fujitsu-ede.com/ Asia Pacific FUJITSU MICROELECTRONICS ASIA PTE LTD #05-08, 151 Lorong Chuan New Tech Park Singapore 556741 Tel: (65) 281-0770 Fax: (65) 281-0220 http://www.fmap.com.sg/ F9803 (c) FUJITSU LIMITED Printed in Japan 32 |
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