FUJITSU SEMICONDUCTOR DATA SHEET DS04-27233-2E ASSP For Power Supply Applications (General Purpose DC/DC Converter) 1-ch DC/DC Converter IC for low voltage MB39A105 ■ DESCRIPTION The MB39A105 is 1-channel DC/DC converter IC using pulse width modulation (PWM). This IC is ideal for up conversion. The minimum operating voltage is low (1.8 V) , and the MB39A105 is best for built-in power supply such as LCD monitors.
MB39A105 ■ PIN ASSIGNMENT (TOP VIEW) −INE 1 8 FB CSCP 2 7 RT VCC 3 6 GND SCPOD 4 5 OUT (FPT-8P-M05) 2
MB39A105 ■ PIN DESCRIPTION Pin No.
MB39A105 ■ BLOCK DIAGRAM VCC 3 −INE 1 VREF Error Amp − + + + SCPOD 4 PWM Comp. Drive Nch − 5 OUT (0.5 V ± 1%) FB 8 IO = 400 mA at VCC = 3.3 V VREF (0.7 V) SCP Comp. + 6 GND (0.3 V) − (0.9 V) + CSCP 2 (1.0 V) − S Q RT Current R OSC bias UVLO L : UVLO release VREF (1.
MB39A105 ■ ABSOLUTE MAXIMUM RATINGS Parameter Symbol Power supply voltage VCC Output current Condition Rating Unit Min Max VCC terminal 7 V IO OUT terminal 35 mA Output peak current IOP Duty ≤ 5% (t = 1/fOSC×Duty) 700 mA Power dissipation PD Ta ≤ +25 °C 490* mW −55 +125 °C Storage temperature TSTG * : The packages are mounted on the epoxy board (10 cm × 10 cm).
MB39A105 ■ ELECTRICAL CHARACTERISTICS (VCC = 3.3 V, Ta = +25 °C) 1. Under voltage lockout protection circuit block [UVLO] Pin No Threshold voltage VTLH 3 Threshold voltage VTH 2 ∆VCSCP 2 Input source current ICSCP 2 CSCP = 0.85 V Reset voltage VRST 3 VCC = 1.1 1.3 1.5 V SCPOD terminal output leak current ILEAK 4 SCPOD = 3.3 V 0 1.0 µA SCPOD terminal output on resistor RON 4 SCPOD = 1 mA 50 100 Ω Oscillation frequency fosc 5 RT = 7.
MB39A105 ■ TYPICAL CHARACTERISTICS Power Supply Current vs. Power Supply Voltage 5.0 Ta = +25 °C RT = 7.5 kΩ Power supply current ICC (mA) Power supply current ICC (mA) 5 4 3 2 1 0 0 2 4 6 8 Power Supply Current vs. RT Terminal Current 10 Ta = +25 °C VCC = 3.3 V 4.5 4.0 3.5 3.0 2.5 2.0 ICC 1.5 1.0 0.5 0.0 0 10 20 30 40 50 RT terminal current IRT (µA) Power supply voltage VCC (V) Error Amplifier Threshold Voltage vs. Power Supply Voltage Error Amplifier Threshold Voltage VTH (V) 1.
MB39A105 Triangular Wave Oscillation Frequency vs. Ambient Temperature 600 10000 Ta = +25 °C VCC = 3.3 V 1000 100 Triangular wave oscillation frequency fOSC (kHz) Triangular wave oscillation frequency fOSC (kHz) Triangular Wave Oscillation Frequency vs. Timing Resistor VCC = 3.3 V RT = 7.5 kΩ 550 500 450 400 −40 10 1 10 100 Timing resistor RT (kΩ) −20 0 20 40 60 80 100 Ambient temperature Ta (°C) Max On Duty vs. Triangular Wave Oscillation Frequency 100 Ta = +25 °C VCC = 3.
MB39A105 (Continued) Power Dissipation vs.
MB39A105 ■ FUNCTIONS 1. DC/DC Converter Functions (1) Triangular-wave oscillator block (OSC) The triangular wave oscillator incorporates a timing resistor connected to RT terminal (pin 7) to generate triangular oscillation waveform amplitude of 0.3 V to 0.7 V. The triangular waveforms are input to the PWM comparator in the IC. (2) Error amplifier block (Error Amp1, Error Amp2) The error amplifier detects the DC/DC converter output voltage and outputs PWM control signals.
MB39A105 2. Power Control Function A switch in series with a resistor connected with the RT terminal (pin 7) allows you to turn on or turn off the power. On/off setting conditions of power supply CTL Power L OFF (standby) H ON (operating) RT ON/OFF CTL (L : OFF, H : ON) 3. Protective Functions (1) Timer-latch short-circuit protection circuit (SCP) Short-circuit detection comparator detects the error amplifier output voltage level.
MB39A105 ■ SETTING THE OUTPUT VOLTAGE • Output Voltage Setting Circuit VO R1 1 + + −INE R2 − Error Amp VO (V) = 0.5 R2 (R1 + R2) (0.5 V) CSCP 2 ■ SETTING THE TRIANGULAR OSCILLATION FREQUENCY The triangular oscillation frequency is determined by the timing resistor (RT) connected to the RT terminal (pin 7) .
MB39A105 ■ SETTING THE SOFT-START TIMES To prevent rush currents when the IC is turned on, you can set a soft-start by connecting soft-start capacitors (CSCP) to the CSCP terminal (pin 2). When IC starts (VCC ≥ UVLO threshold voltage), the external soft-start capacitors (CSCP) connected to CSCP terminal are charged at 11 µA. The error amplifier output (FB (pin 8) ) is determined by comparison between the lower one of the potentials at two non-inverted input terminals (0.
MB39A105 ■ SETTING TIME CONSTANT FOR TIMER-LATCH SHORT-CIRCUIT PROTECTION CIRCUIT The error amplifier’s output level alaways does the comparison operation with the short-circuit protection comparator (SCP Comp.) to the reference voltage. While DC/DC converter load conditions are stable, the short-circuit detection comparator output remains stable, and the CSCP terminal (pin 2) is held at soft-start end voltage (about 0.8 V) .
MB39A105 • Soft-start and short-circuit protection circuit timing chart FB voltage 1.0 V CSCP voltage 0.9 V 0.8 V 0.7 V OSC amplifier Output short Soft-start time tS 0.
MB39A105 ■ I/O EQUIVALENT CIRCUIT 〈〈Soft-start block (CS) 〉〉 〈〈Short-circuit protection circuit block (SCP) 〉〉 VCC 3 VCC ESD protection element ESD protection element 1.0 V 2 CSCP ESD protection element GND 6 〈〈Error amplifier block〉〉 VCC VCC 0.33 V (1.27 V) + − −INE 1 7 RT GND GND 〈〈Output block〉〉 VCC 5 OUT 16 4 SCPOD − GND 〈〈Triangular wave oscillator block (RT) 〉〉 GND + CSCP CS 0.
VIN (1.8 V to 6.0 V) A C8 0.22 µF R4 51 kΩ C9 0.1 µF R7 22 kΩ CSCP FB R5 R6 43 kΩ 330 kΩ −INE VREF (1.0 V) 2 8 1 R S − + ±10% − + 7 3 Q3 RT R1 7.5 kΩ PWM Comp. OSC (0.3 V) (0.7 V) R11 100 kΩ ON/OFF CTL (L : OFF, H : ON) Q (0.9 V) SCP Comp. L : UVLO release UVLO − + VREF Error Amp (0.5 V ± 1%) − + + VCC VREF (1.27 V) bias VREF Power ON/OFF CTL RT Current Drive Nch SCPOD IO = 400 mA at VCC = 3.3 V 4 Q1 C1 C2 C3 R8 0.1 µF 4.7 µF 4.
MB39A105 ■ PARTS LIST COMPONENT ITEM SPECIFICATION VENDOR PARTS No. Q1 Pch FET VDS = 20 V, ID = −2 A (Max) SANYO MCH3306 Q2, Q3 Nch FET VDS = 20 V, Qg = 4.5 nC (Typ) SANYO MCH3405 D1 Diode VF = 0.40 V (Max) , at IF = 1 A SANYO SBS004 L1 Inductor 6.8 µH 1.4 A, 144 mΩ SUMIDA CMD5D13-6R8 C1, C7, C9 C2 to C6 C8 Ceramics Condenser NeoCapacitor Ceramics Condenser 0.1 µF 4.7 µF 0.
MB39A105 ■ SELECTION OF COMPONENTS • Nch MOS FET The N-ch MOSFET for switching use should be rated for at least 20% more than the maximum output voltage. To minimize continuity loss, use a FET with low RDS(ON) between the drain and source. For high output voltage and high frequency operation, on/off-cycle switching loss will be higher so that power dissipation must be considered. In this application, the SANYO MCH3405 is used.
MB39A105 PC = ID 2 × RDS (ON) × Duty = 0.94 2 × 0.16 × =: PS (ON) 9−2.4 9 0.104 W = VD (Max) × ID × tr × fOSC 6 = 9 × 0.94 × 18 × 10−9 × 500 × 103 6 =: 0.013 W PS (OFF) = = =: PT VD (Max) × ID (Max) × tf × fOSC 6 9 × 1.20 × 8 × 10−9 × 500 × 103 6 0.007 W = PC + PS (ON) + PS (OFF) =: 0.104 + 0.013 + 0.007 =: 0.124 W The above power dissipation figures for the MCH3405 is satisfied with ample margin at 0.8 W.
MB39A105 Example: L ≥ ≥ VIN (Max) 2 2IOVO ton 42 × 2 × 0.25 × 9 9−4 9 × 1 500 × 103 ≥ 3.95 µH Inductance values derived from the above formulas are values that provide sufficient margin for continuous operation at maximum load current, but at which continuous operation is not possible at light loads. It is therefore necessary to determine the load level at which continuous operation becomes possible. In this application, the Sumida CMD5D13-6R8 is used. At 6.
MB39A105 Peak-to-peak value: VIN (Min) ton ∆IL = L = 4 × (9 − 4) 1 6.8 × 10−6 × 9 × 500 × 103 =: 0.654 A • Flyback diode The flyback diode is generally used as a Shottky barrier diode (SBD) when the reverse voltage to the diode is less than 40V. The SBD has the characteristics of higher speed in terms of faster reverse recovery time, and lower forward voltage, and is ideal for achieving high efficiency.
MB39A105 • Smoothing Capacitor The smoothing capacitor is an indispensable element for reducing ripple voltage in output. In selecting a smoothing capacitor it is essential to consider equivalent series resistance (ESR) and allowable ripple current. Higher ESR means higher ripple voltage, so that to reduce ripple voltage it is necessary to select a capacitor with low ESR.
MB39A105 ■ REFERENCE DATA Conversion Efficiency vs. Load current Conversion efficiency η (%) 100 Ta = +25 °C 9 V output 90 80 70 Vin = 1.8 V Vin = 3.3 V Vin = 6.0 V 60 50 40 30 1m 10 m 100 m 1 Load current IL (A) Switching Wave Form VG (V) Ta = +25 °C VIN = 3.
MB39A105 ■ USAGE PRECAUTION • Printed circuit board ground lines should be set up with consideration for common impedance. • Take appropriate static electricity measures. • Containers for semiconductor materials should have anti-static protection or be made of conductive material. • After mounting, printed circuit boards should be stored and shipped in conductive bags or containers. • Work platforms, tools, and instruments should be properly grounded.
MB39A105 ■ PACKAGE DIMENSION 8-pin plastic TSSOP (FPT-8P-M05) 0.127±0.03 (.0050±.001) 3.00±0.10(.118±.004) 5 8 4.40±0.10 6.40±0.20 (.173±.004) (.252±.008) INDEX Details of "A" part 1.10(.043)MAX 4 1 "A" 0~8˚ 0.65(.026) 0.22±0.10 (.009±.004) 0.54(.021) 0.10±0.10 (.004±.004) 0.10(.004) 1.95(.
MB39A105 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 and circuit diagrams in this document are presented as examples of semiconductor device applications, and are not intended to be incorporated in devices for actual use.
