Datasheet
Single-chip Type with Built-in FET Switching Regulator Series
Step-down Switching regulators
with Built-in Power MOSFET
BU9002xNUX Series
●General
Description
The BU9002xNUX are a high efficiency 1MHz
synchronous step-down switching regulator with low
current PFM mode.
It provides up to 1.5A load current and an input voltage
range from 4.5V to 5.5V, optimized for various
applications with input voltage range up to 5V.
BU9002xNUX has a mode control pin that allows the
user to select Forced PWM (Pulse Width Modulation)
mode or PFM (Pulse Frequency Modulation) and PWM
auto change mode utilized power save operation at light
load current.
●Features
■
Fast transient response
■
Automatic PFM/PWM operation.
■
Forced PWM operation
■
Internal Soft Start
■
Under voltage lockout
■
Over current protection
■
Thermal shutdown
●
Applications
POL, 1Cell Li-ion battery for portable applications ,
USB accessories
●Package(s)
VSON008X2030
W(Typ.) x D(Typ.) x H(Max.)
2.00mm x 3.00mm x 0.60mm
VSON008X2030
●Typical
Application Circuit(s)
●Lineup
Part No.
BU90023NUX
BU90028NUX
Output
voltage
1.230V
1.175V
Figure 1. Typical Application Circuit(s)
●Pin
Description(s)
●Pin
Configuration(s)
Pin No.
(TOP VIEW)
1
2
LX
MODE
PVIN
VIN
FB
Symbol
LX
MODE
PVIN
VIN
EN
AGND
PGND
FB
Function
Inductor connection pin
Forced PWM mode pin
Power supply input pin
Power supply input pin
Enable pin
GND pin
GND pin
Feedback voltage input pin
3
PGND
4
AGND
EN
5
6
7
8
Figure 2. Pin Configuration(s)
○Product
structure : Silicon monolithic integrated circuit
○This
product is not designed protection against radioactive rays
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21.JUN.2012 Rev.001
TSZ22111・14・001
BU9002xNUX Series
●Block
Diagram(s)
Datasheet
MODE
AVIN
TSD
UVLO
PWM/PFM
control
PVIN
C
Current
sense
FB
-
+
ERROR AMP
Switching
Control Logic
and
Gate Driver
L
LX
C
OUTPUT
VREF
EN
SHUTDOWN
ON/OFF
AGND
Frequency
control
PGND
Figure 3. Block Diagram(s)
●
Description of Block(s)
The BU9002xNUX are a synchronous step-down DC/DC converter that achieves fast transient response from light load to heavy
load by hysteretic PWM control system and current constant PFM control system.
○PWM
control
BU9002xNUX operates by hysteretic PWM control. This scheme ensures fast switching, high efficiency, and fast transient
response.
When the output voltage is below the VREF voltage, the error comparator output is low to high and turning on P-channel
MOSFET until above the VREF voltage and minimum on time.
○PFM
control
At light load the regulator and MODE=low, the regulator operates with reduced switching frequency and improves the efficiency.
During PFM operation, the output voltage slightly higher than typical output voltage.
Figure 4. Operation of PFM mode and PWM mode
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© 2012 ROHM Co., Ltd. All rights reserved.
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TSZ02201-0F2F0AG00020-1-2
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BU9002xNUX Series
●
Description of operations
1) Shutdown
If the EN input pin set to low (<0.4V), all circuit are shut down and the regulator is standby mode.
Do not leave the EN pin floating.
2) Soft start function
The regulator has a soft start circuit that reduces in-rush current at start-up.
Typical start up times with a 2.2uF output capacitor is 240usec.
Datasheet
3) Current limit
The BU9002xNUX has a current limit circuit that protects itself and external components during overload condition.
4) UVLO
The BU9002xNUX has a Under Voltage Lock Out circuit that turn off device when VIN>2.05V(typ.)
5) FORCED PWM MODE
Setting MODE pin high (>1.4V) places the regulator in forced PWM. This control provides noise reduction and output stability.
Do not leave the MODE pin floating.
6) TSD
The BU9002xNUX has a thermal shutdown feature to protect the device if the junction temperature exceeds 150℃.In thermal
shutdown, the DRIVER is disabled.
This circuit is only to cut off the IC from thermal runaway, and has not been design to protect or guarantee the IC. Therefore, the
user should not plan to activate this circuit with continued operation in mind.
●
Absolute Maximum Ratings
(Ta=25℃)
Parameter
Maximum input power supply voltage
Maximum voltage at EN, FB, LX, MODE
Power dissipation
Operating temperature range
Storage temperature range
Junction temperature
Symbol
VIN
VEN, VFB, VLX,
VMODE
Pd
Topr
Tstg
Tjmax
Rating
7
7
0.515
-40 to +85
-55 to +125
+125
Unit
V
V
W
℃
℃
℃
(*1) When mounted on the specified PCB (55mm x 63mm), Deducted by 3.9m W/c when used over Ta=25c
●
Recommended Operating Rating(s)
Rating
Min.
2.3
Typ.
-
Max.
5.5
Parameter
Input voltage
Symbol
VIN
Unit
V
Series
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© 2012 ROHM Co., Ltd. All rights reserved.
TSZ22111・15・001
3/11
TSZ02201-0F2F0AG00020-1-2
21.JUN.2012 Rev.001
BU9002xNUX Series
●Electrical
Characteristic(s)
(unless otherwise specified VIN=5.0V, Ta=25℃)
Item
【Switching
regulator】
Output voltage accuracy
【Soft
start】
Soft start time
【Frequency
control】
Switching frequency
【Driver】
PchFET on resistance
NchFET on resistance
【Control】
EN pin control
voltage
MODE pin
control voltage
【UVLO】
Protect threshold voltage
Hysteresis
【Current
limit】
Current limit threshold
【Output
discharge】
Output discharge resistance
【Circuit
current】
Operating quiescent current
Shutdown current
Uvth
Uvhy
1.95
50
2.05
100
2.15
150
V
mV
Operation
Non Operation
Operation
Non Operation
fosc
0.8
1.0
2.0
MHz
Tss
120
240
480
usec
VOUTA
1.206
1.152
1.230
1.175
1.254
1.199
V
Symbol
Rating
Typ.
Unit
Datasheet
Min.
Max.
Condition
BU90023NUX MODE:H（PWM）
BU90028NUX MODE:H（PWM）
RonP
RonN
VENH
VENL
VMODEH
VMODEL
-
-
1.4
0
1.4
0
250
220
-
-
-
-
400
350
VIN
0.4
VIN
0.4
mOhm
mOhm
V
V
V
V
VIN=5.0V
VIN=5.0V
Forced PWM
Automatic PFM/PWM
ILIMIT
2.2
2.5
2.8
A
PMOS current detect,
Open loop
DRES
55
110
220
Ohm
EN=0V
EN:H, MODE:L,
VOUT=3.6V forced
Not switching
EN=0V
IINS
SHD
-
53
0
75
1
uA
uA
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© 2012 ROHM Co., Ltd. All rights reserved.
TSZ22111・15・001
4/11
TSZ02201-0F2F0AG00020-1-2
21.JUN.2012 Rev.001
BU9002xNUX Series
●
Electrical characteristic curves (Reference data)
BU90023NUX (1.23V OUTPUT）
）
Datasheet
EN
2V/div
EN
2V/div
VOUT
1V/div
VOUT
1V/div
IL
500mA/div
Figure 5. Start up
Figure 6. Shut down
Vout
50mV/div
ac coupled
Vout
50mV/div
ac coupled
IOUT
500mA/div
IOUT
500mA/div
Figure 7. Load transient response 400mA to 800mA
tr=tf=100ns, MODE : Low
Figure 8. Load transient response 600mA to 1200mA
tr=tf=100ns, MODE : Low
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© 2012 ROHM Co., Ltd. All rights reserved.
TSZ22111・15・001
5/11
TSZ02201-0F2F0AG00020-1-2
21.JUN.2012 Rev.001
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