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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
s 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. Also the short-circuit protection detection output function prevents input/output short on a chopper type up-converter. This product is covered by US Patent Number 6,147,477.
s FEATURES
* * * * * * * * * Power supply voltage range : 1.8 V to 6 V Reference voltage accuracy : 1 % High-frequency operation capability : 1 MHz (Max) Built-in standby function: 0 A (Typ) Built-in timer-latch short-circuit protection circuit Built-in short-circuit protection detection output function Built-in soft-start circuit independent of loads Built-in totem-pole type output for Nch MOS FET Package : TSSOP-8P (Thickness 1.1 mm Max)
s PACKAGE
8-pin plastic TSSOP
(FPT-8P-M05)
MB39A105
s PIN ASSIGNMENT
(TOP VIEW)
-INE CSCP VCC SCPOD
1 2 3 4
8 7 6 5
FB RT GND OUT
(FPT-8P-M05)
2
MB39A105
s PIN DESCRIPTION
Pin No. 1 2 3 4 5 6 7 8 Symbol -INE CSCP VCC SCPOD OUT GND RT FB I/O I O O O Descriptions Error amplifiers (Error Amp) inverted input terminal Timer-latch short-circuit protection capacitor connection terminal Power supply terminal Open drain output terminal for short-circuit protection detection During timer-latch short-circuit protection operation : Output "High-Z" During normal operation : Output "L" External Nch FET gate drive terminal Ground terminal Triangular wave oscillation frequency setting resistor connection terminal Error Amplifier (Error Amp) output terminal
3
MB39A105
s BLOCK DIAGRAM
VCC 3 -INE 1
SCPOD 4
VREF
Error Amp - + + (0.5 V 1%)
+ -
PWM Comp.
Drive Nch
5 OUT
FB 8
VREF SCP Comp. + - (0.9 V) (0.7 V) (0.3 V)
IO = 400 mA at VCC = 3.3 V
6 GND
CSCP 2 (1.0 V)
+ - S R OSC UVLO L : UVLO release 10% 7 RT bias VREF (1.27 V) VREF Power ON/OFF CTL Q RT Current
4
MB39A105
s ABSOLUTE MAXIMUM RATINGS
Parameter Power supply voltage Output current Output peak current Power dissipation Storage temperature Symbol VCC IO IOP PD TSTG Condition VCC terminal OUT terminal Duty 5% (t = 1/fOSCxDuty) Ta +25 C Rating Min -55 Max 7 35 700 490* +125 Unit V mA mA mW C
* : The packages are mounted on the epoxy board (10 cm x 10 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.
s RECOMMENDED OPERATING CONDITIONS
Parameter Power supply voltage Input voltage SCPOD terminal output voltage SCPOD terminal output current Output current Oscillation frequency Timing resistor Short-circuit detection capacitor Operating ambient temperature Symbol VCC VINE VSCPOD ISCPOT IO fosc RT CSCP Ta Condition VCC terminal -INE terminal SCPOD terminal SCPOD terminal OUT terminal RT terminal CSCP terminal Value Min 1.8 0 0 0 -30 100 3.3 -30 Typ 500 7.5 0.22 +25 Max 6 VCC - 0.9 6 2 +30 1000 33 1.0 +85 Unit V V V mA mA kHz k F C
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.
5
MB39A105
s ELECTRICAL CHARACTERISTICS
(VCC = 3.3 V, Ta = +25 C) Parameter 1. Under voltage lockout protection circuit block [UVLO]
Symbol
Pin No
Conditions
Value Min 1.15 Typ 1.35 1.00 0.20 Max 1.55 1.05 0.25
Unit
Threshold voltage Threshold voltage Short-circuit detection time setting difference voltage
VTLH VTH VCSCP ICSCP VRST ILEAK RON fosc fOSC/ fOSC ICS VTH IB AV BW VOH VOL ISOURCE ISINK Dtr
3 2 2 2 3 4 4 5 5 2 1 1 8 8 8 8 8 8 5
VCC = CSCP = 0.85 V VCC = SCPOD = 3.3 V SCPOD = 1 mA RT = 7.5 k Ta = 0 C to +85 C CSCP = 0 V FB = 0.5 V -INE = 0 V DC AV = 0 dB FB = 0.5 V FB = 0.5 V RT = 7.5 k OUT = 0 V, Duty 5% (t = 1/foscxDuty) OUT = 3.3 V, Duty 5% (t = 1/foscxDuty) OUT = -15 mA OUT = 15 mA RT = OPEN RT = 7.5 k
V V V A V A kHz % A V nA dB MHz V mV A A %
0.95 0.15
2. Short-circuit protection block [SCP]
Input source current Reset voltage SCPOD terminal output leak current SCPOD terminal output on resistor
-1.76 -0.88 -0.44 1.1 450 -16 0.495 -120 1.17 100 85 1.3 0 50 500 1* -11 0.5 -30 70* 1.1* 1.27 40 -80 300 90 1.5 1.0 100 550 -6 0.505 1.37 200 -50 95
3. Triangular wave oscillator block [OSC]
Oscillation frequency Frequency temperature variation
4. Soft-start block Charge current [CS] Threshold voltage Input bias current Voltage gain 5. Error amplifier Frequency band width block [Error Amp] Output voltage Output source current Output sink current 6. PWM comparator block Maximum duty cycle [PWM Comp.] Output source current 7.Output block [Drive]
ISOURCE
5
-400*
mA
Output sink current
ISINK ROH ROL ICCS ICC
5 5 5 3 3

400* 4.0* 3.0 0 1.2
6.0 10 1.8
mA A mA
Output ON resistor 8. General block Standby current Power supply current
*: Standard design value. 6
MB39A105
s TYPICAL CHARACTERISTICS
Power Supply Current vs. Power Supply Voltage
5
Power Supply Current vs. RT Terminal Current
5.0
Power supply current ICC (mA)
Power supply current ICC (mA)
Ta = +25 C RT = 7.5 k
4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0 10 20 30 ICC
4 3 2 1 0 0 2 4 6 8 10
Ta = +25 C VCC = 3.3 V
40
50
Power supply voltage VCC (V) Error Amplifier Threshold Voltage vs. Power Supply Voltage
1.0
RT terminal current IRT (A)
Error Amplifier Threshold Voltage VTH (V)
0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0 2 4 6
Ta = +25 C VCC = 3.3 V
8
10
Power supply voltage VCC (V) Error Amplifier Threshold Voltage vs. Ambient Temperature Triangular Wave Oscillation Frequency vs. Power supply voltage
Triangular Wave Oscillation Frequency fOSC (kHz)
0.52
600
Error Amplifier Threshold Voltage VTH (V)
VCC = 3.3 V RT = 7.5 k 0.51
Ta = +25 C RT = 7.5 k
550
0.50
500
0.49
450
0.48 -40
-20
0
20
40
60
80
100
400
1
2
3
4
5
6
7
Ambient temperature Ta (C)
Power supply voltage VCC (V)
(Continued)
7
MB39A105
Triangular Wave Oscillation Frequency vs. Timing Resistor Triangular wave oscillation frequency fOSC (kHz)
10000
Triangular Wave Oscillation Frequency vs. Ambient Temperature
600
Triangular wave oscillation frequency fOSC (kHz)
Ta = +25 C VCC = 3.3 V
VCC = 3.3 V RT = 7.5 k 550
1000
500
100
450
10 1 10 100
400 -40
-20
0
20
40
60
80
100
Timing resistor RT (k) Max On Duty vs. Triangular Wave Oscillation Frequency
100 95 Ta = +25 C VCC = 3.3 V
Ambient temperature Ta (C)
Max On Duty (%)
90 85 80 75 70 10 100 1000 10000
Triangular wave oscillation frequency fOSC (kHz) Error Amplifier Gain and Phase vs. Frequency
40 30 20 Ta = +25 C VCC = 3.3 V 180 AV 90
240 k 10 k 1 F
+
10 0 -10 -20 -30 -40 100 1k 10 k 100 k 1M -90 0
Phase (deg)
Gain AV (dB)
IN 10 k
2.4 k
10 11
- + + 1.24 V 9 OUT Error Amp
-180 10 M
Frequency f (Hz)
(Continued)
8
MB39A105
(Continued)
Power Dissipation vs. Ambient Temperature
600
Power dissipation PD (mW)
500 490 400 300 200 100 0 -40
-20
0
20
40
60
80
100
Ambient temperature Ta ( C)
9
MB39A105
s 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. In addition, an arbitrary loop gain can be set by connecting a feedback resistor and capacitor from the output terminal to inverted input terminal of the error amplifier, enabling stable phase compensation to the system. Also, it is possible to prevent rush current at power supply start-up by connecting a soft-start capacitor with the CSCP terminal (pin 2) which is the non-inverted input terminal for Error Amp. The use of Error Amp for soft-start detection makes it possible for a system to operate on a fixed soft-start time that is independent of the output load on the DC/DC converter. (3) PWM comparator block (PWM Comp.) The PWM comparator is a voltage-to-pulse width modulator that controls the output duty depending on the input/ output voltage. The comparator keeps output transistor on while the error amplifier output voltage and the DTC voltage remain higher than the triangular wave voltage. (4) Output block (Drive) The output block is in the totem pole configuration, capable of driving an external N-channel MOS FET.
10
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 H OFF (standby) ON (operating)
ON/OFF CTL (L : OFF, H : ON)
RT
3. Protective Functions
(1) Timer-latch short-circuit protection circuit (SCP) Short-circuit detection comparator detects the error amplifier output voltage level. If the load conditions for the DC/DC converter are stable, the short-circuit protection comparator is kept in equilibrium condition because the error amplifier is free from output variation. At this time the CSCP terminal (pin 2) is held at the soft-start end voltage (about 0.8 V) . If the DC/DC converter output voltage falls and error amplifier output is over 0.9 V, the timer circuits are actuated to start charging the external capacitor CSCP . When the capacitor voltage reaches about 1.0 V, the latch is set and the circuit is turned off the external FET and sets the dead time to 100 %. At this time, latch input is closed and the CSCP terminal is held at the "L" level. To reset the actuated protection circuit, turn off and on the power supply again and set VCC terminal voltage (pin 3) to 1.1 V (Min) or less. (See sSETTING TIME CONSTANT FOR TIMER-LATCH SHORT-CIRCUIT PROTECTION CIRCUIT.) (2) Under voltage lockout protection circuit (UVLO) The transient state or a momentary decrease in supply voltage, which occurs when the power supply is turned on, may cause the IC to malfunction, resulting in breakdown or degradation of the system. To prevent such malfunctions, under voltage lockout protection circuit detects a decrease in internal reference voltage with respect to the power supply voltage, turns off the output FET, and sets the dead time to 100% while holding the CSCP terminal (pin 2) at the "L" level. The circuit restores the output transistor to normal when the supply voltage reaches the threshold voltage of the undervoltage lockout protection circuit. (3) Short-circuit protection detection output function Connecting the Pch MOS FET to SCPOD terminal (pin 4) turns off the Pch MOS FET when the short-circuit protection is detected or under voltage lockout protection circuit operate. This allows you to prevent the shortcircuit between the input and output when the short-circuit protection is detected, thus preventing the input voltage from occurring in the output region in the standby state. (4) Protection circuit operating function table This table refers to output condition when protection circuit is operating. Operating circuit SCPOD Short-circuit protection circuit Under voltage lockout protection circuit High-Z High-Z OUT L L
11
MB39A105
s SETTING THE OUTPUT VOLTAGE
* Output Voltage Setting Circuit
VO
R1 1 -INE - + + (0.5 V) CSCP 2 Error Amp VO (V) = 0.5 R2 (R1 + R2)
R2
s SETTING THE TRIANGULAR OSCILLATION FREQUENCY
The triangular oscillation frequency is determined by the timing resistor (RT) connected to the RT terminal (pin 7) . Triangular oscillation frequency : fosc fosc (kHz) = : 3750 RT (k)
12
MB39A105
s 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 A. The error amplifier output (FB (pin 8) ) is determined by comparison between the lower one of the potentials at two non-inverted input terminals (0.5 V in an internal reference voltage, CSCP terminal voltages) and the inverted input terminal voltage (-INE (pin 1) voltage). The FB terminal voltage is decided for the soft-start period by the comparison between 0.5 V in an internal reference voltage and the voltages of the CSCP terminal. The DC/DC converter output voltage rises in proportion to the CSCP terminal voltage as the soft-start capacitor connected to the CSCP terminal is charged. The soft-start time is obtained from the following formula: Soft-start time: ts (time to output 100%) ts (s) = 0.045 x CSCP (F) :
= 0.8 V : = 0.5 V : =0V :
CSCP terminal voltage Error Amp block -INE voltage
t
Soft-start time (ts)
* Soft-Start Circuit
VO VREF 11 A R1 -INE 1
L priority
R2 - CSCP 2 + + (0.5 V) CSCP 8 FB UVLO Error Amp
13
MB39A105
s 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) . If the load condition changes rapidly due to a short-circuit of the load and the DC/DC converter output voltage drops, the output of the error amplifier usually goes over 0.9 V. In that case, the capacitor CSCP is charged further. When the capacitor CSCP is charged to about 1.0 V, the latch is set and the external FET is turned off (dead time is set to 100%). At this time, the latch input is closed and the CSCP terminal (pin 2) is held at "L" level. When CSCP terminal becomes "L" level, SCPOD terminal Nch MOS FET becomes OFF. SCPOD terminal (pin 4) is held at "L" level and can be used as a short-circuit operating detection signal during normal operation. To reset the actuated protection circuit, the power supply turn off and on again to lower the VCC terminal (pin 3) voltage to 1.1 V (Min) or less. Short-circuit detection time (tCSCP) tCSCP (s) = 0.23 x CSCP (F) :
* Timer-latch short-circuit protection circuit
VO FB 8 R1 Error Amp
-INE
1
R2
- - + (0.5 V)
(0.88 A) (10.1 A)
VREF SCP Comp. - + (0.9 V)
to Drive CSCP 2 - + (1.0 V) VREF SR Latch
UVLO
14
MB39A105
* Soft-start and short-circuit protection circuit timing chart
FB voltage
1.0 V 0.9 V 0.8 V 0.7 V
CSCP voltage
OSC amplifier
0.3 V
Output short
Output short
Soft-start time tS
Short-circuit detection time tCSCP
t
15
MB39A105
s I/O EQUIVALENT CIRCUIT
Soft-start block (CS)
VCC 3
Short-circuit protection circuit block (SCP)
VCC CSCP 1.0 V + -
ESD protection element
GND 6
ESD protection element
2 CSCP
4 SCPOD
ESD protection element
GND
Triangular wave oscillator block (RT)
VCC 0.33 V + - 7 RT GND GND VCC (1.27 V) -INE 1
Error amplifier block
CS 0.5 V
8 FB
Output block
VCC
5 OUT
GND
16
C1 C2 C3 R8 0.1 F 4.7 F 4.7 F 100 k Q1 3 4 L1 6.8 H A Error Amp + - (0.7 V) 6 + (0.3 V) - (0.9 V) + - R OSC bias 10% 7 VREF (1.27 V) VREF Power ON/OFF CTL UVLO L : UVLO release S Q RT Current IO = 400 mA at VCC = 3.3 V GND Drive Nch OUT 5 Q2 C4 C5 C6 C7 4.7 F 4.7 F 4.7 F 0.1 F D1 - + + (0.5 V 1%) VREF SCP Comp. PWM Comp. SCPOD
s APPLICATION EXAMPLE
R5 R6 43 k 330 k -INE
VCC
A
1
R7 22 k
VREF
VO (9.0 V)
R4 51 k C9 0.1 F
8
FB
CSCP
2
VIN (1.8 V to 6.0 V)
C8 0.22 F
(1.0 V)
RT R1 7.5 k Q3
MB39A105
ON/OFF CTL (L : OFF, H : ON) R11 100 k
17
MB39A105
s PARTS LIST
COMPONENT Q1 Q2, Q3 D1 L1 C1, C7, C9 C2 to C6 C8 R1 R4 R5 R6 R7 R8, R11 ITEM Pch FET Nch FET Diode Inductor Ceramics Condenser NeoCapacitor Ceramics Condenser Resistor Resistor Resistor Resistor Resistor Resistor SPECIFICATION VDS = 20 V, ID = -2 A (Max) VDS = 20 V, Qg = 4.5 nC (Typ) VF = 0.40 V (Max) , at IF = 1 A 6.8 H 0.1 F 4.7 F 0.22 F 7.5 k 51 k 43 k 330 k 22 k 100 k 1.4 A, 144 m 50 V 10 V 10 V 0.5 % 0.5 % 0.5 % 0.5 % 0.5 % 0.5 % VENDOR SANYO SANYO SANYO SUMIDA TDK NEC/TOKIN TDK ssm ssm ssm ssm ssm ssm PARTS No. MCH3306 MCH3405 SBS004 CMD5D13-6R8 C1608JB1H104K TEPSLA21A475M8R C1608JB1A224K RR0816P-752-D RR0816P-513-D RR0816P-433-D RR0816P-334-D RR0816P-223-D RR0816P-104-D
Note : SANYO : SANYO Electric Co., Ltd. SUMIDA : SUMIDA Electric Co., Ltd. TDK : TDK Corporation NEC/TOKIN : NEC TOKIN Corporation ssm : SUSUMU Co., Ltd.
18
MB39A105
s 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. Continuity loss, on/off switching loss, and total loss are determined by the following formulas. The selection must ensure that peak drain current does not exceed rated values. Continuity loss : PC PC = ID 2 x RDS(ON) x Duty On-cycle switching loss : PS (ON) VD (Max) x ID x tr x fOSC PS (ON) = 6 Off-cycle switching loss : PS (OFF) VD (Max) x ID (Max) x tf x fOSC PS (OFF) = 6 Total loss : PT PT = PC + PS (ON) + PS (OFF) Example: Using the SANYO MCH3405 Input voltage VIN (Max) = 2.4 V, output voltage VO = 9 V, drain current ID = 0.94 A, Oscillation frequency fOSC = 500 kHz, L = 6.8 H, drain-source on resistance RDS (ON) = 160 m, tr = 18 ns, tf = 8 ns. : Drain current (Max) : ID (Max) VO x IO VIN(Min) ID (Max) = + VIN(Min) 2L = = : 9 x 0.25 2.4 1.20 (A) +
ton x
ton = 1 500 x 103
VO - VIN(Min) t VO
2.4x (9-2.4) 2 x 6.8 x 10-6 x 9
Drain current (Min) : ID (Min) VO x IO VIN(Min) ID (Min) = - VIN(Min) 2L = = : 9 x 0.25 2.4 0.68 (A) -
ton x 1 500 x 103
2.4x (9-2.4) 2 x 6.8 x 10-6 x 9
19
MB39A105
PC = ID 2 x RDS (ON) x Duty 9-2.4 9
= 0.94 2 x 0.16 x = : 0.104 W = =
PS (ON)
VD (Max) x ID x tr x fOSC 6 9 x 0.94 x 18 x 10-9 x 500 x 103 6
= 0.013 W : =
= = :
PS (OFF)
VD (Max) x ID (Max) x tf x fOSC 6 9 x 1.20 x 8 x 10-9 x 500 x 103 6 0.007 W
PT
= 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.
* Inductors
In selecting inductors, it is of course essential not to apply more current than the rated capacity of the inductor, but also to note that the lower limit for ripple current is a critical point that if reached will cause discontinuous operation and a considerable drop in efficiency. This can be prevented by choosing a higher inductance value, which will enable continuous operation under light loads. Note that if the inductance value is too high, however, direct current resistance (DCR) is increased and this will also reduce efficiency. The inductance must be set at the point where efficiency is greatest. Note also that the DC superimposition characteristics become worse as the load current value approaches the rated current value of the inductor, so that the inductance value is reduced and ripple current increases, causing loss of efficiency. The selection of rated current value and inductance value will vary depending on where the point of peak efficiency lies with respect to load current. Inductance values are determined by the following formulas. Inductance value : L VIN2 L ton 2IOVO
20
MB39A105
Example: L VIN (Max) 2 2IOVO
ton 9-4 9 x 1 500 x 103
42 x 2 x 0.25 x 9
3.95 H
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 6.8 H, the load current value under continuous operating conditions is determined by the following formula. Load current value under continuous operating conditions : IO VIN (Max) 2 IO ton 2LVO 42 x 2 x 6.8 x 10-6 x 9 9-4 9 x 1 500 x 103
145.2 mA
To determine whether the current through the inductor is within rated values, it is necessary to determine the peak value of the ripple current as well as the peak-to-peak values of the ripple current that affect the output ripple voltage. The peak value and peak-to-peak value of the ripple current can be determined by the following formulas. Peak value : IL VO x IO IL VIN
+
VIN 2L
ton
ton =
VO - VIN VO
t
Peak-to-peak value : IL VIN IL = ton L Example: Using the CMD5D13-6R8 6.8 H (allowable tolerance 20%) , rated current = 1.4 A Peak value: VO x IO IL VIN 9 x 0.25 2.4
+ +
VIN 2L
ton
ton =
VO - VIN VO
t
2.4 x (9 - 2.4) x 2 x 6.8 x 10-6 x 9
1 500 x 103
1.20 A
21
MB39A105
Peak-to-peak value: VIN (Min) ton IL = L = 4 x (9 - 4) 1 6.8 x 10-6 x 9 x 500 x 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. As long as the DC reverse voltage is sufficiently higher than the output voltage, the average current flowing through the diode is within the mean output current level, and peak current is within peak surge current limits, there is no problem. In this application the SANYO SBS004 is used. The diode mean current and diode peak current can be calculated by the following formulas. Diode mean current : IDi VO-VIN (Min) IDi IO x (1 - ) VO Diode peak current : IDip VO x IO VIN (Min) IDip + ton VIN (Min) 2L Example: Using the SANYO SBS004 VR (DC reverse voltage) = 15 V, mean output current = 1.0 A, peak surge current = 10 A, VF (forward voltage) = 0.40 V, IF = 1.0 A IDi IO x (1 - VO-VIN (Min) ) VO
0.25 x (1 - 0.733) 66.8 mA VO x IO VIN (Min) VIN (Min) ton 2L
IDip
+
1.20 A
22
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. However, the use of a capacitor with low ESR can have substantial effects on loop phase characteristics, and therefore requires attention to system stability. Care should also be taken to use a capacity with sufficient margin for allowable ripple current. This application uses the TEPSLA21A475M8R (NEC/TOKIN) . The ESR, capacitance value, and ripple current can be calculated from the following formulas. Equivalent Series Resistance : ESR VO 1 ESR - IL 2fCL Capacitance value : CL IL CL 2f (VO - IL x ESR) Ripple current : ICL VIN ton ICL L Example: Using the TEPSLA21A475M8R (Three piecies are parallel.) Rated voltage = 10 V, ESR = 500 m, maximum allowable ripple current = 1 Ap-p Equivalent series resistance 1 VO - ESR IL 2fCL 0.18 0.654 - 1 2 x 500 x 103 x 14.1 x 10-6
252.7 m Capacitance value : CL IL CL 2f (VO - IL x ESR) 0.39 2 x 500 x 103 x (0.18 - 0.654 x 0.167)
2.94 F Ripple current : ICL VIN ICL ton L 4 x (9 - 4) 1 x 500 x 103 6.8 x 10-6 x 9
0.654 Ap-p
23
MB39A105
s REFERENCE DATA
Conversion Efficiency vs. Load current
100
Conversion efficiency (%)
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) 10 5 0 VD (V) 15 10 5 0 Ta = +25 C VIN = 3.3 V VO = 9 V IO = 100 mA
0
1
2
3
4
5
6
7
8
9
10 t (s)
24
MB39A105
s 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. * Working personnel should be grounded with resistance of 250 k to 1 M between body and ground. * Do not apply negative voltages. The use of negative voltages below -0.3 V may create parasitic transistors on LSI lines, which can cause abnormal operation.
s ORDERING INFORMATION
Part number MB39A105PFT Package 8-pin plastic TSSOP (FPT-8P-M05) Remarks
25
MB39A105
s PACKAGE DIMENSION
8-pin plastic TSSOP (FPT-8P-M05)
3.000.10(.118.004)
8 5
0.1270.03 (.0050.001)
4.400.10 6.400.20 (.173.004) (.252.008)
INDEX
Details of "A" part 1.10(.043)MAX
1
4
"A"
0~8 0.65(.026) 0.220.10 (.009.004) 0.54(.021) 0.100.10 (.004.004)
0.10(.004) 1.95(.077)
C
2002 FUJITSU LIMITED F08013Sc-1-1
Dimensions in mm (inches)
26
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. 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. The products described in this document are designed, developed and manufactured as contemplated for general use, including without limitation, ordinary industrial use, general office use, personal use, and household use, but are not designed, developed and manufactured as contemplated (1) for use accompanying fatal risks or dangers that, unless extremely high safety is secured, could have a serious effect to the public, and could lead directly to death, personal injury, severe physical damage or other loss (i.e., nuclear reaction control in nuclear facility, aircraft flight control, air traffic control, mass transport control, medical life support system, missile launch control in weapon system), or (2) for use requiring extremely high reliability (i.e., submersible repeater and artificial satellite). 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.
F0209 (c) FUJITSU LIMITED Printed in Japan

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