DS04-27212-2E
FUJITSU SEMICONDUCTOR
DATA SHEET
ASSP For Power Supply Applications
BIPOLAR
Switching Regulator Controller
(Low Voltage)
MB3800
■DESCRIPTION
The MB3800 is a single-channel switching regulator control IC for low voltage applications incorporating a soft
start function and short circuit detection function. The de vice has a low minim um operating v oltage of 1.8 V and
is ideal for the power supply of battery-operated electronic equipment.
■FEATURES
• Wide supply voltage operating range: 1.8 to 15 V
• Low current consumption: Typically 5.5 mA in operation, 1 µA or less in stand-by
• High speed operation is possible: Maximum 1 MHz
• The error amplifier gain is set inside the IC, so peripheral components are minimized.
• Incorporates a soft start circuit.
• Incorporates a timer-latch type short circuit detection circuit (SCP).
• Totem-pole type output with adjustable on/off current (for NPN transistors)
• Incorporates a stand-by function.
• Three types of packages (SOP-8 or SOL-8, SSOP-8)
■PACKAGES
8-pin Plastic SOP
(FPT-8P-M01
8-pin Plastic SOL
(FPT-8P-M02)
8-pin Plastic SSOP
(FPT-8P-M03)
2
MB3800
■PIN ASSIGNMENT
■PIN DESCRIPTION
Pin No. Symbol I/O Description
1 –IN I Error amplifier inverting input pin
2 SCP — Soft start and SCP setting capacitor connection pin
3 VCC — Power supply pin
4 BR/CTL I Output current setting and control pin
5 OUT O Totem-pole type output pin
6 GND — Ground pin
7 OSC — Capacitor and resistor connection pin for setting the oscillation frequency
8 FB O Error amplifier output pin
2
1
4
3
–IN
SCP
V
CC
BR/CTL
OSC
FB
OUT
GND
8
7
6
5
(TOP VIEW)
(FPT-8P-M01)
(FPT-8P-M02)
(
FPT-8P-M03
)
3
MB3800
■BLOCK DIAGRAM
3 7
6 2 4
5
1
8
0.6 V–
0.1 V–
0.1 V
36 kΩ
0.5 V
PWM
Comp.
OUT
–
+
+
1.25 V
Error Amp.
500 Ω
–
+
–IN
FB
GND SCP BR/CTL (8 pin)
DTC 0.6 V 0.3 V
30 kΩ
V CC OSC
+Output drive
control circuit
Soft start SCP
Sawtooth wave
oscillator
Reference
voltage supply
4
MB3800
■ABSOLUTE MAXIMUM RATINGS
(Ta = +25°C)
* :When mounted on a 10 cm square double-sided epoxy board
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 = +25°C)
WARNING: Recommended operating conditions are normal operating ranges for the semiconductor device. All
the device’s electrical characteristics are warranted when operated within these ranges.
Alwa ys use semiconductor devices within the recommended operating conditions . Operation outside
these ranges may adversely affect reliability and could result in device failure.
No warr anty 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 representative beforehand.
Parameter Symbol Condition Rated Value Unit
Min. Max.
Power supply voltage VCC
—
—16V
Output source current IO+— –50 mA
Output sink current IO–—50mA
Allowable dissipation PD
SOP-8, Ta ≤ +25°C — 570* mW
SOP-8, Ta ≤ +25°C — 430* mW
SSOP-8, Ta ≤ +25°C — 580* mW
Operating temperature Top —–30 +85 °C
Storage temperature Tstg –55 +125 °C
Parameter Symbol Values Unit
Min. Typ. Max.
Power supply voltage VCC 1.8 — 15 V
Error amplifier input voltage VI–0.2 — 1.0 V
BR/CTL pin input voltage VBR –0.2 — VCC V
Output source current IO+–40 — — mA
Output sink current IO–——40mA
SCP pin capacitance CPE —0.1—µF
Phase compensation capacitance CP—0.1—µF
Output current setting resistance RB150 390 5000 Ω
Timing resistance RT1.0 3.0 10.0 kΩ
Timing capacitance CT100 270 10000 pF
Oscillation frequency fOSC 10 500 1000 kHz
Operating temperature TOP –30 +25 +85 °C
5
MB3800
■ELECTRICAL CHARACTERISTICS
(VCC = +2 V, Ta = +25°C)
(Continued)
Parameter Symbol Condition Value Unit
Min. Typ. Max.
Circuit to prevent
malfunction at low
input voltage
(U.V.L.O.)
Reset voltage VR——0.9V
Threshold voltage VTH 1.1 1.3 1.5 V
Soft start Charging current ICS VSCP = 0 V –1.5 –1.0 –0.7 µA
Voltage at soft start
completion VtS —0.70.80.9V
Short circuit
detection (S.C.P.) Charging current ICPC VSCP = 0 V –1.5 –1.0 –0.7 µA
Threshold voltage VtPC —0.70.80.9V
Sawtooth wave
oscillator (OSC)
Oscillation frequency fOCS RT = 3.0 kΩ, CT = 270 pF 400 500 600 kHz
Frequency input
stability fdV VCC = 2 V to 15 V — 2 10 %
Frequency variation
with temperature fdT Ta = –30°C to +85°C — 5 — %
Error amplifier
Input threshold
voltage VTVFB = 450 mV 480 500 520 mV
VT input stability VTdV VCC = 2 V to 15 V — 5 20 mV
VT variation with
temperature VTdT Ta = –30°C to +85°C — 1 — %
Input bias current IBVIN = 0 V –1.0 –0.2 1.0 µA
Voltage gain AV— 70 100 145 V/V
Frequency bandwidth BW AV = 0 dB — 6 — MHz
Maximum output
voltage range VOM+—0.78 0.87 — V
VOM–— 0.05 0.2 V
Output source current IOM+VFB = 0.45 V — –40 –24 µA
Output sink current IOM–24 40 — µA
Idle period
adjustment section Maximum duty cycle tDUTY RT = 3.0 kΩ, CT = 270 pF
VFB = 0.8 V 65 75 85 %
—
6
MB3800
(Continued)
■DIAGRAM
Parameter Symbol Condition Value Unit
Min. Typ. Max.
Output section
Output voltage
VOH1 RB = 390 Ω, IO = –15 mA 1.0 1.2 — V
VOH2 RB = 750 Ω, VCC = 1.8 V
IO = –10 mA 0.8 1.0 — V
VOL1 RB = 390 Ω, IO = 15 mA — 0.1 0.2 V
VOL2 RB = 750 Ω, VCC = 1.8 V
IO = 10 mA —0.10.2V
Output source current IO+RB = 390 Ω, VO = 0.9 V — –30 –20 mA
Output sink current IO–RB = 390 Ω, VO = 0.3 V 30 60 — mA
Pull down resistance RO— 203040kΩ
Output current
setting section/
Control section
Pin voltage VBR RB = 390 Ω0.2 0.3 0.4 V
Input off condition IOFF
—
–20 — 0 µA
Input on condition ION — — –45 µA
Pin current range IBR –1.8 — –0.1 mA
Entire device Stand-by current ICCS BR/CTL pin open or VCC —— 1µA
Average supply
current ICC RB = 390 Ω—5.59.3mA
t
S
t
PE
ON
OFF
FB pin voltage
Reference input for short circuit
detection comparator
Idle period setting voltage
Sawtooth wave output
Soft start setting voltage
OUT pin waveforms
SCP pin waveforms
Power supply control SW
Soft start
Output
short
circuit
Output short circuit
Short circuit
detection
7
MB3800
■HOW TO SET THE TIME CONSTANT FOR SOFT START AND SHORT CIRCUIT
DETECTION
1. Soft Start
At pow er on, the capacitor CPE connected to the SCP pin starts charging. The PWM comparator compares the soft
start setting voltage as a proportion of the voltage at the SCP pin with the sawtooth waveform. The comparison
controls the ON duty of the OUT pin, causing the soft start operation. On completion of soft start operation, the
voltage at the SCP pin stays low, the soft start setting vo ltage stays high, and the circuit enters the output short
circuit detection wait state.
Soft start time (The time until the output ON duty reaches approximately 50%)
tS [s] ≅ 0.35 × CPE [µF]
2. Short Circuit Protection
If the switching regulator output suddenly drops due to load effect, the error amplifier output (FB pin) is fixed at
VOM+ and capacitor CPE starts charging. When the voltage at the SCP pin reaches appro ximately 0.8V, the output
pin is set low and the SCP pin stays low.
Once the protection circuit operates, the circuit can be restored by resetting the power supply.
• Short circuit detection time
tPE [s] ≅ 0.8 × CPE [µF]
8
MB3800
■TYPICAL CHARACTERISTICS
(Continued)
10
8
6
4
2
04 8 12 16 20
Supply voltage V CC (V)
Supply current I CC (mA)
1.0
0.8
0.6
0.4
0.2
04 8 12 16 20
Supply voltage V CC (V)
Input threshold voltage V T (V)
Supply voltage vs. Input threshold voltage
T a = +25°C
10
5
0
–10
80 100
Ambient temperature T a (°C)
Input threshold voltage variation ratio ∆V T/V T (%)
Ambient temperature vs. Input threshold
voltage variation ratio
V CC = 2 V
1.0
0.8
0.6
0.4
0.2
00 2.0 3.0 4.0 5.0
Supply voltage V CC (V)
Input threshold voltage V T (V)
Supply voltage vs. Input threshold voltage
T a = +25°C
40 60020–40 –20
–5
2.0
1.6
1.2
0.8
0.4
–10 –20 –30 –40 –50
Hi
g
h level output current I OUT
(
mA
)
High level output voltage V OUT (V)
High level output
V CC = 2 V
R B = 390 Ω
T a = +25°C
500
400
300
200
100
20 40 60 80 100
Hi
g
h level output current I OUT
(
mA
)
Low level output voltage V OUT (mV)
Low level output
V CC = 2 V
R B = 390 Ω
T a = +25°C
00
00
T a = +25°C
R B = 390 Ω
00
1.0 –15
Supply voltage vs. Supply current
9
MB3800
(Continued)
(Continued)
–10
–0.4
BR/CTL pin current I
BR
(mA)
Output source current I
OUT
(mA)
BR/CTL pin current vs. Output source current
00 –0.8 –1.2 –1.6 –2.0
–20
–30
–40
–50
V
CC
= 2 V
V
OUT
= 0.9 V
T
a
= +25°C
100
–0.4
BR/CTL pin current I
BR
(mA)
BR/CTL pin voltage V
BR
(mV)
BR/CTL pin current vs. BR/CTL pin voltage
00 –0.8 –1.2 –1.6 –2.0
200
300
400
500 V
CC
= 2 V
T
a
= +25°C
1.0
–20
BR/CTL pin current I
BR
(
µ
A)
Supply current I
CC
(mA)
BR/CTL pin current vs. Supply current
00 –40 –60 –80 –100
2.0
3.0
4.0
5.0 V
CC
= 2 V
T
a
= +25°C
1 k
Timing resistor R
T
(Ω)
Oscillation frequency f
OSC
(Hz)
Timing resistor vs. Oscillation frequency
10 k
2 k
50 k
500 k
2
Supply voltage V
CC
(V)
Frequency variation ratio ∆f/f (%)
Supply voltage vs. Frequency variation ratio
–150
5
10
–5
0
–10
4 6 8 10 12 14 16
C
T
= 270 pF
R
T
= 3.0 kΩ
T
a
= +25°C
–20
Ambient temperature T
a
(°C)
Frequency variation ratio ∆f/f (%)
Ambient temperature vs. Frequency variation ratio
–15
–40
5
10
–5
0
–10
0 20 40 60 80 100
V
CC
= 2 V
C
T
= 270 pF
R
T
= 3.0 kΩ
5 k
20 k
200 k
5 k2 k
10 k
100 k
1 M
20 k
C
T
= 100 pF
C
T
= 1000 pF
C
T
= 10000 pF
V
CC
= 2 V
T
a
= +25°C
10
MB3800
(Continued)
Oscillation frequency f
OSC
(Hz)
Maximum duty cycle t
DUTY
(%)
Oscillation frequency vs. Maximum duty cycle
0
10 K
100
40
60
20
100 K 1 M
80
0 0.4 0.8 1.2 1.6 2.0 t
(µs)
–50
0
50
0
2
4
6
(V)
(mA)
V
OUT
I
OUT
2 V
10 mV 200 ns
V
CC
= 2 V
C
T
= 270 pF
R
T
= 1.0 kΩ
18 kΩ
2 kΩ
10 µF
I
OUT
(5 V)
390 Ω
V
OUT
22 µH
V
CC
MB3800 5
4
–IN
Output pin voltage and current waveforms
(reference data)
Note: The OFF delay time of V
OUT
depends on the
characteristics of the external transistor.
Measurement circuit diagram
V
CC
= 2 V
C
T
= 270 pF
T
a
= +25°C
11
MB3800
■FUNCTIONAL DESCRIPTION
1. Switching Regulator Function
(1) Reference voltage circuit
The reference voltage circuit generates a temperature-compensated reference voltage (≅1.25V) from voltage
supplied from the pow er supply pin (pin 3). In addition to providing the ref erence v oltage for the s witching regulator ,
the circuit also sets the idle period.
(2) Sawtooth wave oscillator
The sawtooth oscillator gener ates a sawtooth wave (up to 1 MHz) that is stable with respect to the supply voltage
and temperature . The capacitor and resistor that set the oscillation frequency are connected to the OSC pin (pin 7).
(3) Error amplifier (Error Amp.)
The error amplifier detects the output voltage of the switching regulator and outputs the PWM control signal. The
v oltage gain is fixed, and connecting a phase compensation capacitor to the FB pin (pin 8) provides stable phase
compensation for the system.
(4) PWM comparator (PWM Comp.)
The v oltage comparator has one in v erting and three non-inv erting inputs. The comparator is a v oltage/pulse width
conv erter that controls the ON time of the output pulse depending on the input v oltage. The output le v el is high (H)
when the sawtooth wave is lower than the error amplifier output voltage, soft start setting voltage, and idle period
setting voltage.
(5) Output circuit
The output circuit has a totem pole type configuration and can driv e an e xternal NPN transistor directly. The value
of the ON/OFF current can be set by a resistor connected to the BR/CTL pin (pin 4).
2. Power Supply Control Function
Stand-by mode (supply current 1 µA or less) can be set b y connecting the BR/CTL pin (pin 4) to V CC or b y making
the pin open circuit.
SW Mode
OFF Stand-by mode
ON Operating mode
RB
SW
4BR/CTL
MB3800
12
MB3800
3. Other Functions
(1) Soft start and short circuit detection
Soft start operation is set by connecting capacitor CPE to the SCP pin (pin 2). Soft start pre v ents a current spike on
start-up.
On completion of soft start operation, the SCP pin (pin 2) sta ys low and enters the short circuit detection wait state.
When an output short circuit occurs, the error amplifier output is fixed at VOM+ and capacitor CPE starts charging.
After charging to approximately 0.8 V, the output pin (pin 5) is set low and the SCP pin (pin 2) stays low.
Once the protection circuit operates, the circuit can be restored by resetting the power supply. (See “■ HO W TO
SET THE TIME CONSTANT FOR SOFT START AND SHORT CIRCUIT DETECTION”.)
(2) Circuit to prevent malfunction at low input voltage
Transients when po wering on or instantaneous glitches in the supply voltage can lead to malfunction of the control
IC and cause system damage or f ailure . The circuit to prev ent malfunction at lo w input voltage detects a low input
v oltage by comparing the supply v oltage to the internal reference v oltage . On detection, the circuit fix es the output
pin to low.
The system recov ers when the supply voltage rises bac k above the threshold voltage of the malfunction pre vention
circuit.
■APPLICATION EXAMPLE
1
2
4
3
8
7
6
5
MB3800
3 kΩ
22 µH
10 µF
270 pF 0.1 µF
18 kΩ
V o
(5 V)
2 kΩ
0.1 µF
390 Ω
CTL
33 µF
V in
(3 V)
FB
OSC
GND
OUT
–IN
SCP
V
CC
BR/CTL
13
MB3800
■USAGE PRECAUTIONS
1. Do not apply an input voltage greater than the maximum rating.
Do not input voltages greater than the maximum rating as this can cause damage to the LSI.
2. Use in accor dance with the recommended operating conditions.
The electrical characteristics of the LSI are not guaranteed if the input voltage is g reater than the maxim um. Also,
LSI operation is unstable if the input voltage is less than the minimum. Therefore, always use in accordance with
the recommended operating conditions.
3. Use a wide ground line on the printed circuit board.
As the LSI uses a high frequency and theref ore can gener ate high frequency noise , mak e the ground line as wide
as possible.
4. Take anti-static precautions.
• Use a holder for inserting the semiconductor which is anti-static or conductive.
• After mounting the device on a printed circuit board, store or transport the board in a conductive bag or
container.
• Earth work benches, tools, and measuring equipment.
• Ensure that maintenance personnel have a resistance of 250 kΩ to 1 MΩ in series between their body and earth.
14
MB3800
■ORDERING INFORMATION
Part number Package Remarks
MB3800PF 8-pin Plastic SOP
(FPT-8P-M01)
MB3800PNF 8-pin Plastic SOL
(FPT-8P-M02)
MB3800PFV 8-pin Plastic SSOP
(FPT-8P-M03)
15
MB3800
■PACKAGE DIMENSIONS
(Continued)
8-pin Plastic SOP
(FPT-8P-M01)
+0.40
–0.20
+.016
–.008
+0.05
–0.02
+.002
–.001
+0.25
–0.20 +.010
–.008
3.81(.150)REF
1.27(.050)
TYP
INDEX 6.80
.268
0.15
.006
6.35 .250
(.307±.016)(.209±.012)
(.018±.004)
(STAND OFF)
(.020±.008)
0.50±0.20
5.30±0.30 7.80±0.40
0.05(.002)MIN
2.25(.089)MAX
0.45±0.10
Details of "A" part
0.50(.020)
0.20(.008)
0.18(.007)MAX
0.68(.027)MAX
"A"
M
Ø0.13(.005)
0.10(.004)
1994 FUJITSU LIMITED F08002S-4C-4
CDimensions in mm (inches).
16
MB3800
(Continued)
8-pin Plastic SOL
(FPT-8P-M02)
+0.25
–0.20 +.010
–.008
45°
(STAND OFF)
(.020±.008)
Details of "A" part
0.20(.008)
0.40(.016)
0.18(.007)MAX
0.65(.026)MAX
"A"
(.006±.004)
(.197±.012)(.236±.016)
(.154±.012)
(.008±.002)(.017±.004) M
Ø0.13(.005)
0.10(.004)
5.05 .199
3.81(.150)REF
0.40(.016)
5.00±0.30
0.50±.020
6.00±0.40
3.90±0.30
0.15±0.10
1.55±0.20(.061±.008)
0.20±0.050.42±0.101.27(.050)TYP
1994 FUJITSU LIMITED F08004S-2C-4
CDimensions in mm (inches).
17
MB3800
(Continued)
8-pin Plastic SSOP
(FPT-8P-M03)
+0.05
–0.02
+.002
–.001
+0.20
–0.10
+.008
–.004
Details of "A" part
0 10°
(STAND OFF)
0.10±0.10(.004±.004)
(.020±.008)
0.50±0.20
0.80(.0315)
TYP
*
INDEX
"A"
0.10(.004)
0.15
.006
1.25
.049
M
0.10(.004)
(.165±.004) (.244±.008)NOM
(.014±.004)
(.138±.004)
6.20±0.20
5.20(.205)4.20±0.10
2.40(.094)REF
0.35±0.10
3.50±0.10
1994 FUJITSU LIMITED F08005S-1C-2
CDimensions in mm (inches).
MB3800
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.
F9802
FUJITSU LIMITED Printed in Japan
