Fujitsu MB39A105 User manual

DS04-27233-2E
FUJITSU SEMICONDUCTOR
DATA SHEET
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. 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.
■
■■
■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 µA (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)
■
■■
■PACKAGE
8-pin plastic TSSOP
(FPT-8P-M05)

MB39A105
2
■
■■
■PIN ASSIGNMENT
(TOP VIEW)
(FPT-8P-M05)
−INE
CSCP
VCC
SCPOD
1
2
3
4
FB
RT
GND
OUT
8
7
6
5

MB39A105
3
■
■■
■PIN DESCRIPTION
Pin No. Symbol I/O Descriptions
1−INE I Error amplifiers (Error Amp) inverted input terminal
2CSCPTimer-latch short-circuit protection capacitor connection terminal
3VCCPower supply terminal
4SCPODO
Open drain output terminal for short-circuit protection detection
During timer-latch short-circuit protection operation : Output “High-Z”
During normal operation : Output “L”
5 OUT O External Nch FET gate drive terminal
6GNDGround terminal
7RTTriangular wave oscillation frequency setting resistor connection terminal
8 FB O Error Amplifier (Error Amp) output terminal

MB39A105
4
■
■■
■BLOCK DIAGRAM
+
−
−
+
+
+
−
+
−
1
8
2
−INE
FB
CSCP
7
RT
6
5
GND
OUT
43 SCPODVCC
VREF
VREF
Error Amp
SCP
Comp.
PWM
Comp. Drive
Nch
IO=400 mA
at VCC =3.3 V
(0.5 V ±1%)
±10%
(1.0 V)
UVLO
OSC
SQ
R
(0.9 V)
(0.7 V)
(0.3 V)
bias
RT Current
VREF Power ON/OFF
CTL
VREF
(1.27 V)
L : UVLO release

MB39A105
5
■
■■
■ABSOLUTE MAXIMUM RATINGS
* : The packages are mounted on the epoxy board (10 cm ×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.
■
■■
■RECOMMENDED OPERATING CONDITIONS
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.
Parameter Symbol Condition Rating Unit
Min Max
Power supply voltage VCC VCC terminal 7V
Output current IOOUT terminal 35 mA
Output peak current IOP Duty ≤5%(t =1/fOSC×Duty) 700 mA
Power dissipation PDTa ≤+25 °C490* mW
Storage temperature TSTG −55 +125 °C
Parameter Symbol Condition Value Unit
Min Typ Max
Power supply voltage VCC VCC terminal 1.8 6V
Input voltage VINE −INE terminal 0 VCC −0.9 V
SCPOD terminal output voltage VSCPOD SCPOD terminal 0 6V
SCPOD terminal output current ISCPOT SCPOD terminal 0 2mA
Output current IOOUT terminal −30 +30 mA
Oscillation frequency fosc 100 500 1000 kHz
Timing resistor RTRT terminal 3.3 7.5 33 kΩ
Short-circuit detection capacitor CSCP CSCP terminal 0.22 1.0 µF
Operating ambient temperature Ta −30 +25 +85 °C

MB39A105
6
■
■■
■ELECTRICAL CHARACTERISTICS (VCC =3.3 V, Ta =+25 °C)
*: Standard design value.
Parameter Symbol Pin
No Conditions Value Unit
Min Typ Max
1. Under voltage
lockout
protection circuit
block [UVLO]
Threshold voltage VTLH 3VCC=1.15 1.35 1.55 V
2. Short-circuit
protection block
[SCP]
Threshold voltage VTH 20.95 1.00 1.05 V
Short-circuit detection time
setting difference voltage ∆VCSCP 20.15 0.20 0.25 V
Input source current ICSCP 2CSCP=0.85 V −1.76 −0.88 −0.44 µA
Reset voltage VRST 3VCC=1.1 1.3 1.5 V
SCPOD terminal output
leak current ILEAK 4SCPOD=3.3 V 01.0µA
SCPOD terminal output on
resistor RON 4SCPOD=1 mA 50 100 Ω
3. Triangular
wave oscillator
block [OSC]
Oscillation frequency fosc 5 RT =7.5 kΩ450 500 550 kHz
Frequency temperature
variation ∆fOSC/
fOSC 5Ta=0 °C to +85 °C1* %
4.Soft-startblock
[CS] Charge current ICS 2CSCP=0 V −16 −11 −6µA
5. Error amplifier
block [Error Amp]
Threshold voltage VTH 1FB=0.5 V 0.495 0.5 0.505 V
Input bias current IB1−INE =0 V −120 −30 nA
Voltage gain AV8DC 70* dB
Frequency band width BW 8 AV=0 dB 1.1* MHz
Output voltage VOH 81.17 1.27 1.37 V
VOL 840 200 mV
Output source current ISOURCE 8FB=0.5 V −80 −50 µA
Output sink current ISINK 8FB=0.5 V 100 300 µA
6. PWM compar-
ator block
[PWM Comp.] Maximum duty cycle Dtr 5 RT =7.5 kΩ85 90 95 %
7.Output block
[Drive]
Output source current ISOURCE 5OUT =0 V,
Duty ≤5%
(t =1/fosc×Duty) −400* mA
Output sink current ISINK 5OUT =3.3 V,
Duty ≤5%
(t =1/fosc×Duty) 400* mA
Output ON resistor ROH 5OUT=−15 mA 4.0* Ω
ROL 5OUT=15 mA 3.0 6.0 Ω
8. General block Standby current ICCS 3RT=OPEN 010µA
Power supply current ICC 3RT=7.5 kΩ1.2 1.8 mA

MB39A105
7
■
■■
■TYPICAL CHARACTERISTICS
(Continued)
Power supply current ICC (mA)
Power supply current ICC (mA)
Power Supply Current vs. Power Supply Voltage Power Supply Current vs. RT Terminal Current
Power supply voltage VCC (V) RT terminal current IRT (µA)
Error Amplifier Threshold
Voltage VTH (V)
Power supply voltage VCC (V)
Error Amplifier Threshold Voltage vs.
Power Supply Voltage
Error Amplifier Threshold
Voltage VTH (V)
Error Amplifier Threshold Voltage vs.
Ambient Temperature
Ambient temperature Ta (°C)
Triangular Wave Oscillation
Frequency fOSC (kHz)
Ta =+25 °C
RT =7.5 kΩ
5
4
3
2
1
00246810
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0 0 1020304050
Ta =+25 °C
VCC =3.3 V
ICC
Ta =+25 °C
VCC =3.3 V
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0 0246810
VCC =3.3 V
RT =7.5 kΩ
0.52
0.51
0.50
0.49
0.48−40 −20 0 20 40 60 80 100
Ta =+25 °C
RT =7.5 kΩ
600
550
500
450
400 1234567
Triangular Wave Oscillation Frequency vs.
Power supply voltage
Power supply voltage VCC (V)

MB39A105
8
(Continued)
Triangular Wave Oscillation Frequency
vs. Timing Resistor
Triangular wave oscillation
frequency fOSC (kHz)
Timing resistor RT(kΩ)
Triangular Wave Oscillation Frequency
vs. Ambient Temperature
Triangular wave oscillation
frequency fOSC (kHz)
Ambient temperature Ta (°C)
Error Amplifier Gain and Phase
vs. Frequency
Frequency f (Hz)
Max On Duty (%)
Max On Duty vs.
Triangular Wave Oscillation Frequency
Triangular wave oscillation frequency fOSC (kHz)
Ta =+25 °C
VCC =3.3 V
10000
1000
100
10 1 10 100
VCC =3.3 V
RT =7.5 kΩ
600
550
500
450
400−40 −20 0 20 40 60 80 100
Ta =+25 °C
VCC =3.3 V
100
95
90
85
80
75
7010 100 1000 10000
−
+
+
+ 10
11 9
IN OUT
Error Amp
1 µF
1.24 V
10 kΩ
2.4 kΩ
240 kΩ
10 kΩ
40
30
20
10
0
−10
−20
−30
−40
180
90
0
−90
−180
100 1 k 10 k 100 k 1 M 10 M
Ta =+25 °C
VCC =3.3 V
AV
ϕ
Phase φ(deg)
Gain AV(dB)

MB39A105
9
(Continued)
600
500
400
300
200
100
0
490
−40 −20 0 20 40 60 80 100
Power Dissipation vs. Ambient Temperature
Power dissipation PD(mW)
Ambient temperature Ta ( °C)

MB39A105
10
■
■■
■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.)
ThePWMcomparatoris a voltage-to-pulsewidth 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.