Datasheet
0.65V to 5.5V, 1ch
Ultra Low Dropout Linear Regulator Controller
BD3520FVM BD3521FVM
General Description
BD3520FVM, BD3521FVM are ultra-low dropout linear
regulator controllers for chipset that can achieve
ultra-low input to output voltage. By using N-MOSFET
for external power transistor, the controller can be used
at ultra-low I/O voltage difference as low as the voltage
generated by ON-Resistance. By reducing the I/O
voltage difference, large output current is achieved and
conversion loss can be reduced, thus the controller can
be used in replacement of a switching power supply. In
addition, downsizing and cost reduction of the set can
be achieved as suitable power transistor can be
selected depending on the output current. BD3520FVM,
BD3521FVM do not need any choke coil, diode for
rectification and power transistor which are all
necessary in a switching power supply, thus reduced
total cost and compact size can be achieved for the set.
It is also possible to meet the power supply sequence of
the set since output voltage start-up time can be
adjusted by using the NRCS terminal.
Key Specifications
0.65V to 5.5V
4.5V to 5.5V
BD3520FVM 1.2V (Fix)
BD3521FVM 1.5V (Fix)
External FET GATE Drive Current:
±3mA (Typ)
Standby Current:
0µA (Typ)
Operating Temperature Range:
-10°C to +100°C
Drain Voltage Range:
Supply Voltage Range:
Output Voltage:
Package
W(Typ) x D(Typ) x H(Max
)
Features
Reduced rush current by NRCS
Built-in driver for external Nch transistor
Built-in timer latch short protection circuit
Built-in under voltage lock out circuit
Built-in thermal shutdown circuit
MSOP8
2.90mm x 4.00mm x 0.90mm
Applications
Mobile PC, Desktop PC, Digital home appliances
Typical Application Circuit and Block Diagram
VCC
VCC
4
UVLO2
VD
IN
Enable
EN
3
UVLO1
Reference
Block
NRCS
0.65V
0.65V
VD
UVLO
LATCH
8
VREF
UVLO1
EN
G
7
TSD
SCP
UVLO1
UVLO2
EN
VS
6
OUT
Thermal
Protection
TSD
0.65V
VFB
5
SCP
SCP
NRCS
NRCS
1
NRCS
2
GND
○Product
structure：Silicon monolithic integrated circuit
.
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© 2016 ROHM Co., Ltd. All rights reserved.
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product has no designed protection against radioactive rays
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TSZ02201-0J2J0A601270-1-2
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BD3520FVM BD3521FVM
Pin Configuration
TOP VIEW
1
NRCS
GND
EN
VCC
VFB
VS
G
VD
Pin Descriptions
Pin
No.
Pin
Name
Pin Function
NRCS (Non Rush Current on Start up) time
setup. Timer latch setup for Short Circuit
Protection operating time set up Pin.
Ground pin
Enable pin
Power source
Output voltage feedback
Source voltage pin
MOSFET driver output
Drain voltage sense
NRCS
1
8
VD
2
3
GND
EN
VCC
2
7
6
G
4
5
3
VS
6
7
4
5
VFB
8
Description of Operations
1. VCC
BD3520FVM, BD3521FVM has an independent power input pin for the internal circuit operation of the IC. This is used to
bias the IC internal circuit and external N-Channel MOSFET. The voltage used for VCC terminal is 5.0V and maximum
current is 1.7mA.
It is recommended to connect a bypass capacitor with a value of 1µF or more to VCC pin.
2. EN
With an input of 2.0V or higher, the EN terminal turns to “High” level and OUT is produced. At 0.8V or lower, it detects
“Low” level and OUT is turned OFF. Simultaneously, the discharge circuit inside the VS terminal is activated and output
voltage is reduced (150 mA (Min) when V
VS
=1V and V
EN
=0V).
3. VD
The VD terminal is the drain voltage detection terminal of the external N-Channel MOSFET. When drain voltage (IN) is low,
output voltage is turned OFF to prevent under voltage lock out.
Under voltage lock out (UVLO) is reset when drain voltage (IN) reaches 70% of the output voltage. UVLO detects only at
the startup of the EN terminal.
4. VFB
V
VFB
is controlled to achieve as below.
・BD3520FVM
1.2V (typ)
・BD3521FVM
1.5V (typ)
5. NRCS terminal
The NRCS terminal is a constant current output terminal, and operates as
・
Soft-Start ... during start-up
・
SCP-Delay ... after start-up
How to set Soft-Start of NRCS terminal
The output voltage startup time (t
NRCS
) is determined by the time when the NRCS terminal reaches 0.65V. During
start-up, the NRCS terminal serves as a constant current source (I
NRCS
) of 20 µA (Typ) output, and charges externally
connected capacitor (C
NRCS
). Output voltage (V
OUT
) becomes stable when NRCS terminal reaches the internal
reference voltage (0.65V).
How to set NRCS terminal short protection Delay
BD3520FVM, BD3521FVM has short circuit protection (SCP) which is activated when output voltage becomes V
OUT
x
0.35 (typ) or lower. The time when SCP is activated until latch takes place (t
SCP
) is determined by the following
equation:
t
SCP
½
C
NRCS
V
OUTSCP
I
SCP
When SCP is activated, the NRCS terminal provides 20 µA (typ) constant current output (l
SCP
), and charges the
externally connected capacitor (C
NRCS
). When the NRCS terminal reaches 1.3V (V
OSCP
), latch operation is carried out
and output voltage is turned OFF.
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BD3520FVM BD3521FVM
Description of Operations – continued
6. VS
VS terminal is a source voltage detection terminal of the external N-Channel MOSFET. VS terminal has the internal
discharge circuit activated to lower output voltage when EN changes to Low level or various protection circuits (TSD, SCP,
UVLO) are activated.
7. G
G terminal is the gate drive terminal of the external N-Channel MOSFET. Because the output voltage range of G terminal
is up to 5V (VCC), it is necessary to use N-Channel MOSFET whose threshold is lower than “V
CC
- V
OUT
”. In addition, by
including an RC snubber circuit to the G terminal, phase margin of loop gain can be increased and ceramic capacitors can
be used for the terminal.
Absolute Maximum Ratings
(Ta=25°C)
Parameter
Supply Voltage
Drain Voltage
Enable Input Voltage
Power Dissipation
Operating Temperature Range
Storage Temperature Range
Maximum Junction Temperature
Symbol
V
CC
V
VD
V
EN
Pd
Topr
Tstg
Tjmax
Rating
7
(Note 1)
7
7
0.58
(Note 2)
-10 to +100
-55 to +150
+150
Unit
V
V
V
W
°C
°C
°C
(Note 1) However, not exceeding Pd.
(Note 2) To use at temperature above Ta=25°C, derate by 4.7mW/°C
Caution:
Operating the IC over the absolute maximum ratings may damage the IC. The damage can either be a short circuit between pins or an open
circuit between pins and the internal circuitry. Therefore, it is important to consider circuit protection measures, such as adding a fuse, in case
the IC is operated over the absolute maximum ratings.
Recommended Operating Conditions
Parameter
Supply Voltage
Drain Voltage
Enable Input Voltage
Capacitor in NRCS Pin
Symbol
V
CC
V
VD
V
EN
C
NRCS
Rating
Min
4.5
0.65
-0.3
0.001
Max
5.5
5.5
+5.5
1
Unit
V
V
V
µF
Electrical Characteristics
(Unless otherwise specified, Ta=25°C V
CC
=5V V
IN
=3.3V V
EN
=3V )
Standard Value
Parameter
Symbol
Min
Typ
Max
Circuit Current
Shut Down Mode Current
Output Voltage 1
Output Voltage 2
Line Regulation
Load Regulation
[Enable]
High Level Enable Input Voltage
Low Level Enable Input Voltage
Enable Pin Input Current
(Note) Not 100% tested
Unit
mA
µA
V
V
%/V
mV
V
V
µA
V
EN
=3V
V
EN
=0V
Conditions
I
CC
I
ST
V
OUT
V
OUT2
Reg.l
Reg.L
V
ENHI
V
ENLOW
I
EN
BD3520FVM
BD3521FVM
BD3520FVM
BD3521FVM
-
-
1.188
1.485
1.176
1.470
-
-
2
-0.3
-
0.85
0
1.200
1.500
1.200
1.500
0.1
0.5
-
-
7
1.7
10
1.212
1.515
1.224
1.530
0.5
10
V
CC
+0.8
10
I
OUT
=50mA
VCC=4.5V to 5.5V
Ta=-10°C to 100°C
(Note)
V
CC
=4.5V to 5.5V
I
OUT
=0A to 3A
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BD3520FVM BD3521FVM
Electrical Characteristics- continued
(Unless otherwise specified, Ta=25°C V
CC
=5V V
IN
=3.3V V
EN
=3V)
Standard Value
Parameter
Symbol
Min
Typ
Max
[Source Voltage]
VS Input Bias Current
VS Standby Current
[Output MOSFET Driver]
MOSFET Driver Source Current
MOSFET Driver Sink Current
[UVLO]
VCC UVLO
VCC UVLO Hysterisis
VD UVLO
[Drain Voltage Sensing]
VD Input Bias
Current
[NRCS/SCP]
NRCS Charge Current
SCP Charge Current
SCP Discharge Current
SCP Threshold Voltage
Short Detect Voltage
NRCS Stand-by Voltage
I
NRCS
I
SCPCH
I
SCPDI
V
SCP
V
OSCP
V
STB
14
14
0.3
1.2
-
20
20
-
1.3
-
26
26
-
1.4
50
µA
µA
mA
V
V
mV
V
NRCS
=0.5V
V
NRCS
=0.5V
V
NRCS
=0.5V
BD3520FVM
BD3521FVM
I
VD
10
7
16
13
22
19
μA
VD=3.3V
V
CCUVLO
V
CCHYS
V
VDUVLO
4.20
100
4.35
160
4.50
220
V
mV
V
VCC: Sweep up
VCC: Sweep down
VD: Sweep up
I
GSO
I
GSI
2
2
3
3
4
4
mA
mA
V
VFB
=V
OUT
– 0.1V,
V
GATE
=2.5V
V
VFB
= V
OUT
+ 0.1V,
V
GATE
=2.5V
I
SBIAS
I
SSTB
-
150
1.2
-
2.4
-
mA
mA
V
VS
=1V V
EN
=0V
Unit
Conditions
V
OUT
x0.6 V
OUT
x0.7 V
OUT
x0.8
V
OUT
x0.3 V
OUT
x0.35 V
OUT
x0.4
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BD3520FVM BD3521FVM
Typical Performance Curves
1.40
1.40
1.20
Standby Current : I
STB
(µA)
1.00
Circuit Current : I
CC
(mA)
1.20
1.00
0.80
0.60
0.80
0.40
0.60
0.20
0.00
-60
-10
40
Ta(℃)
Temperature : Ta
90
140
0.40
4.5
4.7
4.9
(°C)
Supply Voltage : V
CC
(V)
Figure 2. Circuit Current vs Supply Voltage
5.1
VCC(V)
5.3
5.5
Figure 1. Standby Current vs Temperature
1.220
1.215
1.520
1.515
Output Voltage : V
OUT
(V)
Output Voltage : V
OUT
(V)
-10
0
10
20 30
40
50 60 70
80
90 100
1.210
1.205
1.200
1.510
1.505
1.500
1.195
1.190
1.185
1.495
1.490
1.485
1.480
-10
0
10
20
30
40
50
60
70
80
90 100
1.180
Temperature : Ta (°C)
Figure 3. Output Voltage vs Temperature
(BD3520FVM)
Temperature : Ta (°C)
Figure 4. Output Voltage vs Temperature
(BD3521FVM)
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TSZ02201-0J2J0A601270-1-2
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