FUJITSU SEMICONDUCTOR DATA SHEET DS04-27208-1E 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 µA or less during standby Built-in high-precision reference voltage generator: 2.50 V±1% 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) ■ 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 ■ PIN ASSIGNMENT Cb1 VE1 OUT1 VCC2 OUT2 VE2 GND VE3 OUT3 OUT4 VE4 Cb4 (TOP VIEW) 48 47 46 45 44 43 42 41 40 39 38 37 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 18 19 20 21 22 23 24 –IN3 (C) Ca3 SCP 34 CTL3 3 CTL2 Ca2 CTL1 Cb3 VREF 35 VCC1 2 CT Cb2 RT Ca4 OSCOUT 36 OSCIN 1 –IN2 (C) Ca1 (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 MB3785A ■ PIN DESCRIPTION Pin No. CH1 CH2 CH3 CH4 Symbol I/O Description 1 Ca1 — 48 Cb1 — 7 +IN1(E) I CH1 error amp non-inverted input pin. 6 –IN1(E) I CH1 error amp inverted input pin. 5 FB1 O CH1 error amp output pin. 8 –IN1(C) I CH1 comparator inverted input pin. 4 DTC1 I CH1 dead time control pin. 47 VE1 I CH1 output current setting pin. 46 OUT1 O CH1 totem-pole output pin. 3 Ca2 — 2 Cb2 — CH2 output transistor OFF-current setting pin. Insert a capacitor between the Ca2 and the Cb2 pins, then set the output transistor OFF-current. 12 +IN2(E) I CH2 error amp non-inverted input pin. 11 –IN2(E) I CH2 error amp inverted input pin. 10 FB2 O CH2 error amp output pin. 13 –IN2(C) I CH2 comparator inverted input pin. 9 DTC2 I CH2 dead time control pin. 43 VE2 I CH2 output current setting pin. 44 OUT2 O CH2 totem-pole output pin. 34 Ca3 — 35 Cb3 — CH3 output transistor OFF-current setting pin. Insert a capacitor between the Ca3 and the Cb3 pins, then set the output transistor OFF-current. 25 +IN3(E) I CH3 error amp non-inverted input pin. 26 –IN3(E) I CH3 error amp inverted input pin. 27 FB3 O CH3 error amp output pin. 24 –IN3(C) I CH3 comparator inverted input pin. 28 DTC3 I CH3 dead time control pin. 41 VE3 I CH3 output current setting pin. 40 OUT3 O CH3 totem-pole output pin. 36 Ca4 — 37 Cb4 — CH4 output transistor OFF-current setting pin. Insert a capacitor between the Ca4 and the Cb4 pins, then set the output transistor OFF-current. 30 +IN4(E) I CH4 error amp non-inverted input pin. 31 –IN4(E) I CH4 error inverted input pin. 32 FB4 O CH4 error amp output pin. 29 –IN4(C) I CH4 comparator inverted input pin. CH1 output transistor OFF-current setting pin. Insert a capacitor between the Ca1 and the Cb1 pins, then set the output transistor OFF-current. (Continued) 3 MB3785A (Continued) Pin No. Power Supply Circuitt Triangular-Wave Oscillator Circuit CH4 Symbol I/O Description 33 DTC4 I CH4 dead time control pin. 38 VE4 I CH4 output current setting pin. 39 OUT4 O CH4 totem-pole output pin. 14 OSCIN — 15 OSCOUT — 16 RT — This pin connects to a resistor for setting the triangular-wave frequency. 17 CT — This pin connects to a capacitor for setting the triangular-wave frequency. 18 VCC1 — Power supply pin for the reference power supply control circuit. 45 VCC2 — Power supply pin for the output circuit. 42 GND — GND pin. 19 VREF O 23 SCP — 20 CTL1 I This pin connects a ceramic resonator. Reference voltage output pin. This pin connects to a capacitor for the short-circuit protection circuit. Power supply circuit and first-channel control pin. Control Circuit 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. 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 ■ BLOCK DIAGRAM Ca1 1 CH 1 Error Amp 1 +IN1 (E) 7 + –IN1 (E) FB1 6 – 5 –IN1 (C) 8 DTC1 4 VREF + 48 Cb1 PWM comparator 1 + Comparator 1 OFF Current Setting – – + – VREF 2.5 V + –IN2 (E) FB2 11 – 10 VREF + –IN2 (C) 13 DTC2 9 PWM comparator 2 Comparator 2 – VREF DTC Comparator 2 –IN3 (E) 26 – FB3 27 –IN3 (C) 24 DTC3 28 –IN4 (E) 31 – FB4 32 OUT3 41 VE3 Ca4 36 37 PWM comparator 4 Cb4 OFF Current Setting + + – 39 100 Ω + OUT4 – 2.5 V SCP Comparator 1 µA 23 VE2 40 100 Ω Comparator 4 0.6 V SCP 43 Cb3 2.5 V + 33 OUT2 – 30 DTC4 44 OFF Current Setting + + – + +IN4 (E) 29 Ca2 Cb2 33 Ca3 CH 4 Error Amp 4 –IN4 (C) 2 PWM comparator 3 Comparator 3 0.6 V VE1 34 CH 3 Error Amp 3 + 47 2V 2.5 V 25 OUT1 OFF Current Setting – – + + – +IN3 (E) 46 3 CH 2 Error Amp 2 12 VCC2 DTC 2V Comparator 1 – +IN2 (E) 45 – – – –+ 38 VE4 22 CTL2 CTL3 18 VCC1 20 CTL1 21 2.1 V DTC Comparator 3 – – + –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 CTL1 CTL2 CTL3 Power supply circuit First channel 4th chanSecond channel 3rd andnels H H L H H L L On/Off state of channel ON ON OFF L X ON OFF ON OFF Standby state* * : The power supply current value during standby is 10 µA 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 = +25°C) Parameter Symbol Conditions Rating Unit Power supply voltage VCC — 20 V Control input voltage VICTL — 20 V Power dissipation PD Ta ≤ +25°C 550* mW Operating ambient temperature TOP — –30 to 85 °C Storage temperature Tstg — –55 to 125 °C * : The packages are mounted on the epoxy board (4 cm × 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. ■ RECOMMENDED OPERATING CONDITIONS (Ta = +25°C) 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 kΩ 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. 8 MB3785A ■ ELECTRICAL CHARACTERISTICS (VCC = +6 V, Ta = +25°C) Parameter Reference voltage block Reference voltage 3 CH/4 CH 1 CH/2 CH Under voltage lockout protection circuit (U.V.L.O) Short-circuit detection comparator Short circuit detection block VREF Conditions IOR = –1 mA Value Unit Min. Typ. Max. 2.475 2.500 2.525 V Rate of changed in output voltage vs. Temperature ∆VREF /VREF Ta = –30°C to +85°C –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 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–1.8 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 µA Oscillation frequency fOSC CT = 300 pF, RT = 6.2 kΩ 450 500 550 kHz Frequency stability (VCC) ∆f/fdv VCC = 3.6 V to 18 V — ±1 — % Frequency stability (Ta) ∆f/fdT Ta = –30°C to +85°C –4 — 4 % (Continued) 9 MB3785A (Continued) (VCC = +6 V, Ta = +25°C) General Output block Channel control block 3 CH/4 CH dead time control circuit 1 CH/2 CH dead time control circuit Error amplifier Parameter 10 Symbol Conditions Value Min. Typ. Max. Unit 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–1.8 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 µA Latch mode source current IIdt Vdt = 1.5 V — –500 –80 µA Latch input voltage VIdt Idt = –40 µA 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 µA Latch mode source current IIdt Vdt = 1.5 V 80 500 — µA Latch input voltage VIdt Idt = +40 µA — 0.2 0.3 V Threshold voltage Vth 0.7 1.4 2.1 V Input current — IIH VCTL = 5 V — 100 200 µA IIL VCTL = 0 V –10 — 10 µA — –40 — mA — Source current IO Sink current IO RE = 82 Ω 18 30 42 mA Output leakage current ILO VO = 18 V — — 20 µA Standby current ICC0 — — 0 10 µA Supply current when output off ICC — — 6 8.6 mA MB3785A ■ TYPICAL CHARACTERISTIC CURVES 1. Supply current vs. Supply voltage 5 Ta = +25°C 8 Reference voltage VREF (V) Supply current ICC (mA) 10 2. Reference voltage vs. Supply voltage CTL1 = 6 V 6 CTL1, 2 = 6 V, CTL1, 2, 3 = 6 V 4 2 0 0 4 8 12 16 4 3 2 1 0 20 Ta = +25°C 0 4 8 Supply voltage VCC (V) 4 VREF 3 3 2 2 VE 1 1 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) 5 Ta = +25°C 1 20 4. Reference voltage vs. Ambient temperature Voltage on Output Current — Setting Pin VE (V) 5 0 16 Supply voltage VCC (V) 3. Reference voltage and Output current setting pin voltage vs. Supply voltage 4 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 = 6 V Ta = +25°C 2.8 2.6 2.4 2.2 2.0 0 1 2 3 Control voltage VCTL1 (V) 4 5 VCC = 6 V Ta = +25°C 500 Control current ICTL1 (µA) 3.0 Reference voltage VREF (V) 6. Control current vs. Control voltage 400 300 200 100 0 0 4 8 12 16 20 Control voltage VCTL1 (V) (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 50 102 5 × 102 103 5 × 103104 5 × 104105 VCC = 6 V Ta = +25°C 1M 500 K 100 K 50 K CT = 68 pF CT = 150 pF 10 K CT = 300 pF 5K Timing capacitance CT (pF) CT = 15000 pF 1K 5 K10 K Timing resistance RT (Ω) 9. Triangular wave cycle vs. Timing capacitance 10. Duty vs. Triangular wave frequency VCC = 6 V RT = 10 kΩ Ta = +25°C 100 80 5 1 0.5 60 40 20 0 0.2 10 102 5 × 102 103 5 × 103 104 5 K 10 K 5 × 104 50 K 100 K 500 K 1 M Triangular wave frequency (Hz) Timing capacitance CT (pF) 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 –40 –20 0 20 40 60 Ambient temperature Ta (°C) 80 100 Rate of change in triangular Wave frequency (%) 10 10 Rate of change in triangular Wave frequency (%) VCC = 6 V VDT = 1.60 V Ta = +25°C CH 1 10 Duty Dtr (%) Triangular wave cycle TOSC (µsec) 100 50 –10 CT = 1500 pF 50 K100 K 500 K 1 M VCC = 6 V fOSC = 450 kHz (RT = 8.5 kΩ, CT = 250 pF) 5 0 –5 –10 –40 –20 0 20 40 60 80 100 Ambient temperature Ta (°C) (Continued) 12 MB3785A (Continued) Ta = +25°C 20 180 90 Aϑ 0 0 φ –20 Phase φ (deg) –90 –40 –180 1K 10 K 100 K 1M 10 M 3.0 VCC = 6V Ta = +25°C 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 kΩ 240 kΩ 4.7 kΩ – IN OUT 10 µF – + + 4.7 kΩ 4.7 kΩ Error amp 15. Power dissipation vs. Ambient temperature 1000 Power dissipation Pd (mW) Gain AV (dB) 40 Error amp maximum output voltage amplitude (V) 14. Error amp maximum output voltage vs. Frequency 13. Gain vs. Frequency and Phase vs. Frequency 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 Channels 1 and 2: When Output Voltage (VO) is Positive VREF VOUT+ R VO+ = – R1 VREF 2 × R2 (R1 + R2) + – R R2 RNF 2. Method of Connecting Channels 1 and 2: When Output Voltage (VO) is Negative VREF VO– = – R R1 + – R R2 RNF VOUT– 14 VREF 2 × R1 (R1 + R2) + VREF MB3785A 3. Method of Connecting Channels 3 and 4: When Output Voltage (VO) is Positive VREF VOUT R VO + = R1 VREF 2 × R2 (R1 + R2) + – R R2 RNF 4. Method of Connecting Channels 3 and 4: When Output Voltage (VO) is Negative VREF V O– = – R VREF 2 × 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 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 Figure 2. Output Current Waveform Drive transistor CB ON-current Output current OFF-current OFF-current setting block 0 OFF-current ON-current VE RE t Figure 3. Voltage and Current Waveforms on Output Pin (CH1) Figure 4. Measuring Circuit Diagram VCC = 10 V VO (V) 10 1000 pF VCC 1 0 48 8 pin 22 µH 45 40 IO MB3785A IO (mA) 20 570 pF 10 µF 8.2 k 2.7 k 0 47 –20 –40 0 0.4 0.8 1.2 t (µS) 16 46 VO 1.6 2.0 82 Ω 7 pin (5 V) MB3785A ■ 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 × 10–6/CPE 0.65 = 50 mV + tPE × 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 µA 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 18 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 5-10% 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 (msec) • Ceramic Resonator Turn-on Characteristic VCT (V) 2.0 1.5 1.0 0 1 2 3 t (msec) 20 MB3785A ■ 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 × 100 [%], Vdt = R2 R1 + R2 × 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 traingular-wave amplitude ≅ 0.6 V and triangular-wave maximum voltage ≅ 1.9 V is given below. Duty (OFF) ≅ 1.9 –Vdt 0.6 × 100 [%], Vdt = R2 R1 + R2 × 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 Figure 12. When Not Using DTC VREF 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. 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 19 VREF Rdt Cdt Rdt DTC3 (DTC4) DTC1 (DTC2) Cdt 22 VREF 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 19 Cdt Figure 16. Setting Dead Time and Soft Start for CH3 and CH4 19 VREF R1 R1 DTC3 (DTC4) DTC1 (DTC2) R2 VREF Cdt R2 23 MB3785A ■ 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 L Tr RC VIN D RL C Figure 18. Gain-Frequency Characteristic Figure 19. Phase-Frequency Characteristic 20 0 –20 (2) –40 100 –180 1k Frequency f (Hz) 24 (1) (2) : RC = 31 mΩ (1) (2) : RC = 31 mΩ 10 (2) –90 (1) : RC = 0 Ω (1) : RC = 0 Ω –60 Phase (deg) Gain (dB) 0 10 k 100 k 10 100 1k Frequency f (Hz) 10 k 100 k MB3785A (Reference Data) The phase margin is halved by changing the smoothing capacitor from an aluminum electrolytic capacitor (RC = 1.0 Ω) to a small-ESR semiconductor electrolytic capacitor (OS – CON; RC = 0.2 Ω). (See Figure 21 and 22.) Figure 20. DC/DC Converter AV-φ Characteristic Measuring Circuit VOUT VO+ CNF AV–ø characteristic between this interval –IN + FB – +IN VIN R2 R1 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 VCC = 10 V RL = 25 Ω CP = 0.1 µF ϕ AV 20 62° 0 V O+ 90 0 –20 –40 180 –90 10 100 1k Phase (deg) Gain (dB) 40 + Al electrolytic capacitor 220 µF (16 V) – RC ≅ 1.0 Ω : FOSC = 1 kHz GND –180 100 k 10 k Frequency f (Hz) Figure 22. Phase-Frequency Characteristic Gain - frequency and phase frequency characteristics of OS – CON (DC/DC converter +5 V output) 60 VO+ 90 20 ϕ 27° 0 –20 –40 180 0 Phase (deg) Gain (dB) VCC = 10 V RL = 25 Ω CP = 0.1 µF AV 40 –90 10 100 1k 10 k + OS – CON 22 µF (16 V) – RC ≅ 0.2 Ω : fOSC = 1 kHz GND –180 100 k Frequency f (Hz) 25 MB3785A ■ EXAMPLE OF APPLICATION CIRCUIT 33 µF VCC 10 µH 1000 pF 1 33 µF 48 A +IN 4.7 kΩ 150 kΩ 4.7 kΩ –IN FB 45 7 6 CHI 1000 pF 8.2 kΩ 2.7 kΩ 10 mA A 47 DTC 10 µF OUT 8 33 kΩ 5V 46 5 RFB B VCC B 22 µH 4 250 Ω 1000 pF 3 1 µF 24 V 27 kΩ 2 C +IN 4.7 kΩ –IN 12 D 15 V 11 CH2 FB 150 kΩ 4.7 kΩ 10 44 RFB OUT 1000 pF 20 kΩ 10 mA D 15 µF 1.8 kΩ 13 27 kΩ DTC C 43 250 Ω 9 1000 pF Motor Control Signal 1 µF –IN 25 10 µF CH3 27 40 RFB F 1000 pF 28 250 Ω 1000 pF H 36 22 µH 37 +IN G –IN 30 10 µF 32 CH4 RFB H 39 1000 pF 250 Ω 33 VCC 18 VREF 19 GND 0.1 µF 10 mA G 38 10 kΩ SCP 8.2 kΩ 2.7 kΩ OUT 29 DTC DC motor 31 FB 150 kΩ 42 23 14 15 16 RT 20 17 CT 300 pF CTL1 21 CTL2 22 CTL3 6.2 k Ceramic Resonator 26 10 mA E 41 10 kΩ Motor Control Signal 2.7 kΩ OUT 24 DTC 8.2 kΩ 26 FB 150 kΩ DC motor 22 µH 35 +IN E F 34 33 kΩ Output Control Signals MB3785A ■ 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. ■ ORDERING INFORMATION Part number MB3785APFV Package Remarks 48-pin plastic LQFP (FPT-48P-M05) 27 MB3785A ■ PACKAGE DIMENSION 48-pin Plastic LQFP (FPT-48P-M05) +0.20 1.50 0.10 9.00±0.20(.354±.008)SQ +.008 36 (MOUNTING HEIGHT) .059 .004 7.00±0.10(.276±.004)SQ 25 37 24 5.50 (.217) REF 8.00 (.315) NOM INDEX Details of "A" part 48 13 1 12 "A" LEAD No. 0.50±0.08 (.0197±.0031) 0.18 +0.08 0.03 0.127 0.02 .007 +.003 .001 +0.05 .005 .001 +.002 0.10±0.10 (STAND OFF) (.004±.004) 0.50±0.20 (.020±.008) 0.10(.004) C 0 10˚ 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 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 FUJITSU LIMITED Printed in Japan 32 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.