FUJITSU SEMICONDUCTOR DATA SHEET DS04-27208-4E ASSP BIPOLAR Switching Regulator Controller (4 Channels plus High-Precision, High-Frequency Capabilities) MB3785A 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. 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 * 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. (Continued) PACKAGE 48-pin, Plastic LQFP (FPT-48P-M05) MB3785A (Continued) * Adjustable dead time over the entire duty ratio range * Built-in standby and output control functions * High-density mounting possible: 48-pin LQFP package PIN ASSIGNMENT (TOP VIEW) OUT1 Cb1 48 47 OUT2 VCC2 VE1 46 45 GND 44 OUT3 VE3 VE2 42 1 37 36 Ca4 Cb2 2 35 Cb3 Ca2 3 34 Ca3 DTC1 4 33 DTC4 FB1 5 32 FB4 -IN1 (E) 6 31 -IN4 (E) +IN1 (E) 7 30 +IN4 (E) -IN1 (C) 8 29 -IN4 (C) DTC2 9 28 DTC3 FB2 10 27 FB3 -IN2 (E) 11 26 -IN3 (E) +IN2 (E) 12 25 +IN3 (E) 13 14 15 16 17 -IN2(C) OSCOUT OSCIN RT CT 18 19 VREF VCC1 20 40 21 39 Cb4 Ca1 43 41 VE4 OUT4 22 38 23 24 CTL2 SCP CTL1 CTL3 -IN3 (C) (FPT-48P-M05) Note : The alphabetic characters in parenthesis indicate the following input pins. (C) : comparator (E) : error amp 2 MB3785A PIN DESCRIPTION Pin No. CH1 CH2 CH3 CH4 Symbol I/O Description 1 Ca1 -- 48 Cb1 -- CH1 output transistor OFF-current setting terminal. Insert a capacitor between the Ca1 and the Cb1 terminals, then set the output transistor OFF-current. 7 +IN1(E) I CH1 error amp non-inverted input terminal. 6 -IN1(E) I CH1 error amp inverted input terminal. 5 FB1 O CH1 error amp output terminal. 8 -IN1(C) I CH1 comparator inverted input terminal. 4 DTC1 I CH1 dead time control terminal. 47 VE1 I CH1 output current setting terminal. 46 OUT1 O CH1 totem-pole output terminal. 3 Ca2 -- 2 Cb2 -- CH2 output transistor OFF-current setting terminal. Insert a capacitor between the Ca2 and the Cb2 terminals, then set the output transistor OFF-current. 12 +IN2(E) I CH2 error amp non-inverted input terminal. 11 -IN2(E) I CH2 error amp inverted input terminal. 10 FB2 O CH2 error amp output terminal. 13 -IN2(C) I CH2 comparator inverted input terminal. 9 DTC2 I CH2 dead time control terminal. 43 VE2 I CH2 output current setting terminal. 44 OUT2 O CH2 totem-pole output terminal. 34 Ca3 -- 35 Cb3 -- CH3 output transistor OFF-current setting terminal. Insert a capacitor between the Ca3 and the Cb3 terminals, then set the output transistor OFF-current. 25 +IN3(E) I CH3 error amp non-inverted input terminal. 26 -IN3(E) I CH3 error amp inverted input terminal. 27 FB3 O CH3 error amp output terminal. 24 -IN3(C) I CH3 comparator inverted input terminal. 28 DTC3 I CH3 dead time control terminal. 41 VE3 I CH3 output current setting terminal. 40 OUT3 O CH3 totem-pole output terminal. 36 Ca4 -- 37 Cb4 -- CH4 output transistor OFF-current setting terminal. Insert a capacitor between the Ca4 and the Cb4 terminals, then set the output transistor OFF-current. 30 +IN4(E) I CH4 error amp non-inverted input terminal. 31 -IN4(E) I CH4 error inverted input terminal. 32 FB4 O CH4 error amp output terminal. 29 -IN4(C) I CH4 comparator inverted input terminal. (Continued) 3 MB3785A (Continued) Pin No. Power Supply Circuit Triangular-Wave Oscillator Circuit CH4 Symbol I/O Description 33 DTC4 I CH4 dead time control terminal. 38 VE4 I CH4 output current setting terminal. 39 OUT4 O CH4 totem-pole output terminal. 14 OSCIN -- 15 OSCOUT -- 16 RT -- This terminal connects to a resistor for setting the triangular-wave frequency. 17 CT -- This terminal connects to a capacitor for setting the triangular-wave frequency. 18 VCC1 -- Power supply terminal for the reference power supply control circuit. 45 VCC2 -- Power supply terminal for the output circuit. 42 GND -- GND terminal. 19 VREF O Reference voltage output terminal. 23 SCP -- This terminal connects to a capacitor for the short-circuit protection circuit. This terminal connects a ceramic resonator. Power supply circuit and CH1 control terminal. Control Circuit 20 CTL1 I 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. CH2 control terminal. While the CTL1 terminal is High 21 CTL2 I 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. CH3 and CH4 control terminal. While the CTL1 terminal is High 22 4 CTL3 I 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. MB3785A BLOCK DIAGRAM Ca1 1 CH 1 Error Amp 1 +IN1 (E) -IN1 (E) FB1 7 + 6 - 5 -IN1 (C) 8 DTC1 4 VREF + 48 Cb1 - - + + Comparator 1 - PWM comparator 1 OFF Current Setting VREF -IN2 (E) FB2 - 2.5 V 12 + 11 - 10 VREF + -IN2 (C) 13 DTC2 9 PWM comparator 2 - - + + Comparator 2 - -IN3 (E) 26 - FB3 27 VREF DTC Comparator 2 -IN3 (C) 24 DTC3 28 31 - FB4 32 -IN4 (C) 29 DTC4 33 SCP 23 41 VE3 Ca4 Cb4 OFF Current Setting + + - 39 100 - - - - -+ OUT3 37 PWM comparator 4 2.5 V 1 A VE2 36 + SCP Comparator 43 40 100 Comparator 4 0.6 V OUT2 Cb3 CH 4 Error Amp 4 -IN4 (E) 44 OFF Current Setting + + - 2.5 V + Ca2 Cb2 33 Ca3 - 30 2 PWM comparator 3 + +IN4 (E) VE1 34 Comparator 3 0.6 V 47 2V CH 3 Error Amp 3 + OUT1 OFF Current Setting 2.5 V 25 46 3 - +IN3 (E) VCC2 DTC 2V Comparator 1 CH 2 Error Amp 2 +IN2 (E) 45 38 VE4 22 CTL2 CTL3 18 VCC1 20 CTL1 21 2.1 V DTC Comparator 3 - - + OUT4 -1.9 V -1.3 V 1.2 V VREF S R SR Latch Under Voltage Lock-out Protection Circuit Ref. Power Supply Vol. Circuit & Channel Circuit Control Triangular-Wave Oscillator Circuit 2.5 V OSCIN 14 15 16 RT 17 CT 19 VREF 42 GND OSCOUT Ceramic Resonator 5 MB3785A 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 On/Off state of channel CTL1 CTL2 CTL3 CH1 CH2 H H L H H L L Power supply circuit ON ON OFF L X CH3 and CH4 ON OFF ON OFF Standby state* *: 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 ABSOLUTE MAXIMUM RAGINGS (See WARNING) (Ta = +25C) Parameter Symbol Conditions Power supply voltage VCC Control input voltage Rating Unit Min Max -- -- 20 V VICTL -- -- 20 V Power dissipation PD Ta +25C -- 550* mW Operating ambient temperature TOP -- -30 85 C Storage temperature Tstg -- -55 125 C *: The packages are mounted on the epoxy board (4 cm x 4 cm). WARNING: Semiconductor devices can be permanently damaged by application of stress (voltage, current, temperature, etc.) in excess of absolute maximum ratings. Do not exceed these ratings. RECOMMENDED OPERATING CONDITIONS (Ta = +25C) Parameter Symbol Conditions VCC Error amp. input voltage Comparator input voltage Value Unit Min Typ Max -- 4.5 6.0 18 V VI -- -0.2 -- VCC -0.8 V VI -- -0.2 -- VCC V VICTL -- -0.2 -- 18 V Output current IO -- 3.0 -- 30 mA Timing capacitance CT -- 68 -- 1500 pF Timing resistance RT -- 5.1 -- 100 k Oscillation frequency fOSC -- 100 500 1000 kHz Operating ambient temperature TOP -- -30 25 85 C Power supply voltage* Control input voltage *: The minimum value of the recommended supply voltage is 3.6 V except when the device operates with constant output sink current. WARNING: The recommended operating conditions are required in order to ensure the normal operation of the semiconductor device. All of the device's electrical characteristics are warranted when the device is operated within these ranges. Always use semiconductor devices within their recommended operating condition ranges. Operation outside these ranges may adversely affect reliability and could result in device failure. No warranty is made with respect to uses, operating conditions, or combinations not represented on the data sheet. Users considering application outside the listed conditions are advised to contact their FUJITSU representatives beforehand. 8 MB3785A ELECTRICAL CHARACTERISTICS Parameter Reference voltage block Reference voltage CH 3/CH 4 CH 1/ CH 2 Under voltage lockout protection circuit (U.V.L.O) Short-circuit detection comparator Short circuit detection block VREF Conditions IOR = -1 mA Min 2.475 2.500 2.525 V Rate of changed in output voltage vs. Temperature VREF /VREF Ta = -30C to +85C -2 0.2 2 % Input stability Line VCC = 3.6 V to 18 V -10 -2 10 mV Load stability Load IOR = -0.1 mA to -1 mA -10 -3 10 mV VREF = 2 V -25 -8 -3 mA Sort-circuit output current Triangular waveform oscillator block Symbol (VCC = +6 V, Ta = +25C) Value Unit Typ Max IOS VtH -- -- 2.72 -- V VtL -- -- 2.60 -- V VHYS -- 80 120 -- mV Reset voltage (VCC) VR -- 1.5 1.9 -- V Input threshold voltage Vth -- 2.45 2.50 2.55 V Input bias current IIB -200 -100 -- nA Input voltage range VI -- -0.2 -- VCC V Input offset voltage VIO -- 0.58 0.65 0.72 V Input bias current IIB -200 -100 -- nA Threshold voltage Hysteresis width VI = 0 V VI = 0 V Common mode input voltage range VICM -- -0.2 -- VCC-0.8 V Threshold voltage VtPC -- 0.60 0.65 0.70 V Input standby voltage VSTB -- -- 50 100 mV Input latch voltage VI -- -- 50 100 mV Input source current Ilbpc -- -1.4 -1.0 -0.6 A Oscillation frequency fOSC CT = 300 pF, RT = 6.2 k 450 500 550 kHz Frequency stability (VCC) f/fdv VCC = 3.6 V to 18 V -- 1 -- % Frequency stability (Ta) f/fdT Ta = -30C to +85C -4 -- 4 % (Continued) 9 MB3785A (Continued) General Output block Channel control block CH 3/ CH 4 dead CH 1/ CH 2 dead time control time control circuit circuit Error amplifier Parameter 10 Symbol Conditions Min (VCC = +6 V, Ta = +25C) Value Unit Typ Max Input offset voltage VIO VFB = 1.6 V -10 -- 10 mV Input bias current IIB VFB = 1.6 V -200 -100 -- nA Common mode input voltage range VICM -- -0.2 -- VCC-0.8 V Voltage gain AV -- 60 100 -- dB Frequency bandwidth BW AV = 0 dB -- 800 -- kHz Vt0 Duty cycle = 0 % -- 1.9 2.25 V 1.05 1.3 -- V Input threshold voltage Vt100 Duty cycle = 100 % Input bias current IIbdt Vdt = 2.3 V -- 0.1 0.5 A Latch mode source current IIdt Vdt = 1.5 V -- -500 -80 A Latch input voltage VIdt Idt = -40 A VREF-0.3 2.4 -- V Vt0 Duty cycle = 0 % 1.05 1.3 -- V Input threshold voltage Vt100 Duty cycle = 100 % -- 1.9 2.25 V Input bias current IIbdt Vdt = 2.3 V -- 0.1 0.5 A Latch mode source current IIdt Vdt = 1.5 V 80 500 -- A Latch input voltage VIdt Idt = +40 A -- 0.2 0.3 V Threshold voltage Vth 0.7 1.4 2.1 V Input current -- IIH VCTL = 5 V -- 100 200 A IIL VCTL = 0 V -10 -- 10 A -- -40 -- mA Source current IO Sink current IO RE = 82 18 30 42 mA Output leakage current ILO VO = 18 V -- -- 20 A Standby current ICC0 -- -- 0 10 A Supply current when output off ICC -- -- 6 8.6 mA -- MB3785A TYPICAL CHARACTERISTIC CURVES 1. Supply current vs. Supply voltage Ta = +25C 8 Ta=+25C 5 Reference voltage VREF (V) 10 Supply current ICC (mA) 2. Reference voltage vs. Supply voltage CTL1 = 6 V 6 CTL1, 2 = 6 V, CTL1, 2, 3 = 6 V 4 2 0 4 3 2 1 0 0 4 8 12 16 20 0 4 8 Supply voltage VCC (V) 3 3 2 2 VE 1 1 0 2 3 4 5 2.56 VCC = 6 V VCTL1, 2, 3 = 6 V IOR = -1 mA 2.54 Reference voltage VREF (V) Reference voltage VREF (V) 4 VREF Voltage on Output Current -- Setting Pin VE (V) 5 4 1 20 4. Reference voltage vs. Ambient temperature Ta = +25C 0 16 Supply voltage VCC (V) 3. Reference voltage and Output current setting pin voltage vs. Supply voltage 5 12 2.52 2.50 2.48 2.46 2.44 -60 Supply voltage VCC (V) -40 -20 0 20 40 60 80 100 Ambient temperature Ta (C) 5. Reference voltage vs. Control voltage VCC = 6V Ta = +25C 500 VCC = 6 V Ta = +25C Control current ICTL1 (A) Reference voltage VREF (V) 3.0 6. Control current vs. Control voltage 2.8 2.6 2.4 2.2 400 300 200 100 0 2.0 0 1 2 3 Control voltage VCTL1 (V) 4 5 0 4 8 12 16 Control voltage VCTL1 (V) 20 (Continued) 11 MB3785A (Continued) 8. Triangular wave frequency vs. Timing resistance 7. Triangular wave maximum amplitude voltage vs. Timing capacitance 5M VCC = 6 V RT = 10 k Ta = +25 C 2.2 2.0 Triangular wave frequency fOSC (Hz) Triangular - wave maximum amplitude voltage VMAX (V) 2.4 1.8 1.6 1.4 1.2 1.0 0.8 5 x 102 103 50 102 5 x 103 104 5 x 104 105 VCC = 6 V Ta = +25C 1M 500 k 100 k 50 k C T = 68 pF C T = 150 pF 10 k C T = 300 pF 5k C T = 1500 pF Timing capacitance CT (pF) C T= 15000 pF 1k 5 k 10k 50 k 100 k 500 k 1 M Timing resistance RT () 9. Triangular wave cycle vs. Timing capacitance 100 VCC = 6 V RT = 10 k Ta = +25C 10. Duty vs. Triangular wave frequency 100 80 10 Duty Dtr (%) Triangular wave cycle TOSC (s) 50 5 VCC = 6 V VDT = 1.6 V Ta = +25C CH 1 60 40 1 20 0.5 0 0.2 10 10 5 x 10 10 5 x 10 10 Timing capacitance CT (pF) 2 2 3 3 5 x 10 4 5k 4 10 Rate of change in triangular Wave frequency (%) 10 Rate of change in triangular Wave frequency (%) 500 k 1 M 12. Rate of change in triangular wave frequency vs. Ambient temperature (Using ceramic resonator) 11. Rate of change in triangular wave frequency vs. Ambient temperature (Not using ceramic resonator) VCC = 6 V fOSC = 460 kHz (RT = 6.8 k, CT = 280 pF) 5 0 -5 -10 10k 50 k 100 k Triangular wave frequency (Hz) 0 -5 -10 -40 -20 0 20 40 60 Ambient temperature Ta (C) 80 100 VCC = 6 V fOSC = 450 kHz (RT = 8.5 k, CT = 250 pF) 5 -40 -20 0 20 40 60 80 100 Ambient temperature Ta (C) (Continued) 12 MB3785A (Continued) Ta = +25C 40 Gain AV (dB) 90 AV 0 0 -20 Phase (deg) 20 180 -90 --80 -40 1k 10 k 100 k 1M 10 M Error amp maximum output voltage amplitude (V) 14. Error amp maximum output voltage vs. Frequency 13. Gain vs. Frequency and Phase vs. Frequency 3.0 VCC = 6V Ta = +25C CH 1 2.0 1.0 0 100 500 1 k 5 k 10 k 50 k 100 k 500 k 1 M Triangular wave frequency fOSC (Hz) Frequency f (Hz) [Measuring Circuit] 2.5 V 2.5 V 4.7 k 240 k 4.7 k - IN OUT 10 F - + + 4.7 k 4.7 k Error amp 15. Power dissipation vs. Ambient temperature Power dissipation Pd (mW) 1000 800 600 550 LQFP 400 200 0 -30 -20 0 20 40 60 80 100 Ambient temperature Ta (C) 13 MB3785A METHODS OF SETTING THE OUTPUT VOLTAGE 1. Method of Connecting CH1 and CH2: When Output Voltage (VO) is Positive VREF VOUT+ R V O+ = - R1 VREF 2 x R2 (R1 + R2) + - R R2 RNF 2. Method of Connecting CH1 and CH2: When Output Voltage (VO) is Negative VREF V O- = - R R1 + - R R2 RNF VOUT- 14 VREF 2 x R1 (R1 + R2) + VREF MB3785A 3. Method of Connecting CH3 and CH4: When Output Voltage (VO) is Positive VREF VOUT R VO+ = R1 VREF 2 x R2 (R1 + R2) + - R R2 RNF 4. Method of Connecting CH3 and CH4: When Output Voltage (VO) is Negative VREF VO- = - R VREF 2 x R1 (R1 + R2) + VREF R1 + - R R2 RNF VOUT- 15 MB3785A METHOD OF SETTING THE OUTPUT CURRENT The output circuit is comprised of a totem-pole configuration. Its output current waveform is such that the ONcurrent 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 Figure 2. Output Current Waveform Drive transistor CB ON-current Output current OFF-current OFF-current setting block 0 OFF-current ON-current RE t VE Figure 3. Voltage and Current Waveforms on Output Pin (CH1) Figure 4. Measuring Circuit Diagram VCC = 10 V 200 ns 5V VO [ V ] 10 1000 pF VCC 1 0 48 45 IO [ mA ] 40 IO 20 MB3785A 46 570 pF 0 -20 47 10 mV -40 0 0.4 0.8 1.2 t [ s ] 16 8 pin 22 H 1.6 2.0 82 VO 10 F 8.2 kW 2.7 kW 7 pin (5 V) MB3785A METHOD OF SETTING TIME CONSTANT FOR TIMER/LATCH-ACTUATED SHORT-CIRCUTING 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 (s) 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 - - - + 23 S R OUT Q1 Q2 Latch U.V.L.O PWM comparator CPE 2.1 V 17 MB3785A 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 OSCILLATOR FREQUENCY SETTING The oscillator frequency can be set by connecting a timing capacitor (CT) to the CT terminal (pin 17) and a timing resistor (RT) to the RT terminal (pin 16). Oscillator frequency: fosc fosc (kHz) 18 930000 CT(pF) RT(k) MB3785A 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 OSCOUT RT CT 14 15 16 17 CT RT 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% to 10% lower than that of the ceramic resonator. Figure 8. When Using Ceramic Resonator OSCIN 14 OSCOUT 15 Ceramic resonator C1 RT 16 CT 17 RT CT C2 19 MB3785A <Precautions> When the oscillation rise time at power switch-on is compared between a ceramic and a crystal resonator, it is known that the crystal resonator is about 10 to 100 times slower to rise than the ceramic resonator. Therefore, when a crystal resonator is used, system operation as a switching regulator at power switch-on becomes unstable. To avoid this problem, it is recommended that you use a ceramic oscillator because it has a short rise time and, hence, ensures stable operation. * Crystal Resonator Turn-on Characteristic VCT (V) 2.0 1.5 1.0 0 1 2 3 4 5 4 5 t (ms) * Ceramic Resonator Turn-on Characteristic VCT (V) 2.0 1.5 1.0 0 1 2 3 t (ms) 20 MB3785A METHOD OF SETTING THE 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 19 Figure 10. When Not Using DTC VREF R1 DTC1 (DTC2) DTC1 (DTC2) Vdt R2 (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 triangular-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 19 VREF Figure 12. When Not Using DTC 19 VREF R1 DTC3 (DTC4) Vdt DTC3 (DTC4) R2 <Precautions> When you use a ceramic resonator, pay attention when setting the dead time because the triangular-wave amplitude is determined by the values of CT and RT. 22 MB3785A METHODS OF SETTING THE SOFT START TIME To prevent surge currents when the IC is turned on, you can set a soft start using the DTC terminal (pin 4, 9, 28 and 33). When power is switched on, channels 1 and 2 begin discharging the capacitor (Cdt) connected the DTC1 (DTC2) terminal, channels 3 and 4 begin charging the capacitor (Cdt) connected the DTC3 (DTC4) terminal. The soft start process operates by comparing the soft start setting voltage, which is proportional to the DTC terminal voltage, with the triangular waveform, and varying the ON-duty of the OUT terminal (pin 46, 44, 40 and 39). The soft start time until the ON duty reaches 50 % is determined by the following equation: For figure 13 Soft start time (time until output ON duty = 50%) ts (s) = - Cdt (F) x Rdt () x ln ( 1.6 ) 2.5 0.446 x Cdt (F) x Rdt () For figure 14 Soft start time (time until output ON duty = 50%) ts (s) = - Cdt (F) x Rdt () x ln (1 - 1.6 ) 2.5 1.022 x Cdt (F) x Rdt () Figure 13. Setting Soft Start for CH1 and CH2 19 19 VREF VREF Rdt Cdt Rdt Figure 14. Setting Soft Start for CH3 and CH4 DTC3 (DTC4) DTC1 (DTC2) Cdt 23 MB3785A It is also possible to set soft start simultaneously with the dead time by configuring the DTC terminals as shown below. For figure 15 Soft start time (time until output ON duty = 50%) ts (s) = - Cdt (F) x R1 () x R2 () R1 () + R2 () x ln (0.64 - 0.36R2 () ) R1 () For figure 16 Soft start time (time until output ON duty = 50%) ts (s) = - Cdt (F) x R1 () x R2 () R1 () + R2 () x ln (1 - 1.6 (R1 () + R2 ()) ) 2.5R2 () Figure 15. Setting Dead Time and Soft Start for CH1 and CH2 19 Cdt Figure 16. Setting Dead Time and Soft Start for CH3 and CH4 19 VREF R1 R1 DTC3 (DTC4) DTC1 (DTC2) R2 24 VREF Cdt R2 MB3785A APPLICATION 1. Equivalent series resistor and stability of smoothing capacitor The equivalent series resistor (ESR) of the smoothing capacitor in the DC/DC converter greatly affects the loop phase characteristic. The stability of the system is improved so that the phase characteristic may advance the phase to the ideal capacitor by ESR in the high frequency region (see "Gain vs. Frequency" and "Phase vs. Frequency"). A smoothing capacitor with a low ESR reduces system stability. Use care when using low ESR electrolytic capacitors (OS-CONTM) and tantalum capacitors. Note: OS-CON is the trademark of Sanyo Electnic Co., Ltd. DC/DC Converter Basic Circuit L Tr RC VIN D RL C Gain vs. Frequency Phase vs. Frequency 0 0 -20 -40 -60 10 (2) (1) : RC = 0 (2) : RC = 31 m 100 (2) -90 -180 (1) 1k 10 k Frequency f (Hz) Phase (deg) Gain AV (dB) 20 100 k 10 (1) : RC = 0 (2) : RC = 31 m 100 1k 10 k Frequency f (Hz) (1) 100 k 25 MB3785A Reference data If an aluminum electrolytic smoothing capacitor (RC =: 1.0 ) is replaced with a low ESR electrolytic capacitor (OS-CONTM : RC =: 0.2 ), the phase margin is reduced by half (see Fig. 17 and 18). DC/DC Converter AV vs. characteristic Test Circuit VOUT VO+ CNF AV vs. characteristic Between these points - FB + -IN VIN +IN R2 R1 VREF/2 Error Amp. Figure 17 DC/DC Converter +5 V output Gain vs. Phase VCC = 10 V RL = 25 CP = 0.1 F 40 180 20 90 62 0 0 -20 -40 10 100 1k Figure 18 VCC = 10 V RL = 25 CP = 0.1 F Gain AV (dB) 40 20 GND 180 90 0 27 -20 0 -90 100 AI Capacitor 220 F (16 V) RC 1.0 : fOSC = 1 kHz DC/DC Converter +5 V output Gain vs. Phase AV 26 + - -180 100 k 10 k 60 -40 10 VO+ -90 Phase (deg) Gain AV (dB) AV Phase (deg) 60 1k Frequency f (Hz) 10 k -180 100 k VO+ + - OS-CONTM 22 F (16 V) RC 0.2 : fOSC = 1 kHz GND MB3785A EXAMPLE OF APPLICATION CIRCUIT 33 F VCC 10 H 1000 pF 1 33 F 48 A +IN 4.7 k -IN 150 k 4.7 k FB 45 7 6 CH1 1000 pF 8.2 k 2.7 k 10 mA A 47 DTC 10 F OUT 8 33 k 5V 46 5 RFB B VCC B 22 H 4 250 1000 pF 3 1 F 24 V 27 k 2 C +IN 4.7 k -IN 12 D 15 V 11 CH2 FB 150 k 4.7 k 10 44 RFB OUT 1000 pF 20 k 10 mA D 15 F 1.8 k 13 27 k DTC C 43 250 9 1000 pF Motor Control Signal 1 F -IN 25 10 F CH3 27 40 RFB F 1000 pF 10 mA E 41 28 10 k Motor Control Signal 2.7 k OUT 24 DTC 250 1000 pF H 36 22 H 37 +IN G -IN 30 10 F 32 CH4 RFB H 39 8.2 k 2.7 k OUT 1000 pF 10 mA G 29 DTC DC motor 31 FB 150 k 8.2 k 26 FB 150 k DC motor 22 H 35 +IN E F 34 33 k 38 250 33 10 k VCC 18 VREF 19 GND SCP 0.1 F 42 23 14 15 16 RT 20 17 CT 300 pF CTL1 21 CTL2 22 CTL3 6.2 k Ceramic Resonator Output Control Signals 27 MB3785A NOTES ON USE * Take account of common impedance when designing the earth line on a printed wiring board. * Take measures against static electricity. - For semiconductors, use antistatic or conductive containers. - When storing or carrying a printed circuit board after chip mounting, put it in a conductive bag or container. - The work table, tools and measuring instruments must be grounded. - The worker must put on a grounding device containing 250 k to 1 M resistors in series. * Do not apply a negative voltage - Applying a negative voltage of -0.3 V or less to an LSI may generate a parasitic transistor, resulting in malfunction. ORDERING INFORMATION Part number MB3785APFV 28 Package 48-pin plastic LQFP (FPT-48P-M05) Remarks MB3785A PACKAGE DIMENSION Note 1) * : These dimensions include resin protrusion. Note 2) Pins width and pins thickness include plating thickness. Note 3) Pins width do not include tie bar cutting remainder. 48-pin Plastic LQFP (FPT-48P-M05) 9.000.20(.354.008)SQ +0.40 +.016 *7.00 -0.10 (.276 -.004 )SQ 36 0.1450.055 (.006.002) 25 24 37 0.08(.003) Details of "A" part +0.20 1.50 -0.10 +.008 13 48 "A" 0~8 LEAD No. 1 0.50(.020) C (Mounting height) .059 -.004 INDEX 0.100.10 (.004.004) (Stand off) 12 0.200.05 (.008.002) 0.08(.003) M 0.500.20 (.020.008) 0.600.15 (.024.006) 0.25(.010) 2002 FUJITSU LIMITED F48013S-c-6-10 Dimensions in mm (inches) Note : The values in parentheses are reference values. 29 MB3785A FUJITSU LIMITED 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, such as descriptions of function and application circuit examples, in this document are presented solely for the purpose of reference to show examples of operations and uses of Fujitsu semiconductor device; Fujitsu does not warrant proper operation of the device with respect to use based on such information. When you develop equipment incorporating the device based on such information, you must assume any responsibility arising out of such use of the information. Fujitsu assumes no liability for any damages whatsoever arising out of the use of the information. Any information in this document, including descriptions of function and schematic diagrams, shall not be construed as license of the use or exercise of any intellectual property right, such as patent right or copyright, or any other right of Fujitsu or any third party or does Fujitsu warrant non-infringement of any third-party's intellectual property right or other right by using such information. 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Please note that Fujitsu will not be liable against you and/or any third party for any claims or damages arising in connection with above-mentioned uses of the products. Any semiconductor devices have an inherent chance 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 Law of Japan, the prior authorization by Japanese government will be required for export of those products from Japan. F0308 FUJITSU LIMITED Printed in Japan