UM3521DA
600mA, 2.25MHz, Synchronous Step-Down DC-DC Converter
UM3521DA
DFN6 2.0
×
1.8
General Description
The UM3521DA is a high efficiency synchronous step down dc/dc converter optimized for battery
powered applications. It provides up to 600mA output current from a single Li-ion cell and is ideal
to power mobile phones and other portable applications. With wide input voltage range of 2.0V to
5.5V, the device supports applications powered by Li-ion batteries with extended voltage range,
two and three cell alkaline batteries 3.3V and 5V input voltages rails. The UM3521DA operates at
2.25MHz fixed switching frequency and enters Power Save Mode operation at light load current
to maintain high efficiency over the entire load current range. The Power Save Mode is optimized
for low output voltage ripple. For low noise applications, the device can be forced into fixed
frequency PWM mode by pulling the MODE pin high. In the shutdown mode, the current
consumption is reduced to less than 1uA. UM3521DA allows the use of small inductors and
capacitors to achieve a small solution size.
Applications
Cellular Telephones
PDA, Pocket PCs
Wireless and DSL Modems
Low Power DSP Supply
Portable Media Players
POL applications
Features
High Efficiency Step Down Converter
Output Current up to 600mA
Wide Vin Range from 2.0V to 5.5V for
Li-ion Batteries
2.5MHz Fixed Frequency Operation
Power Save Mode at Light Load Currents
Voltage Positioning in PFM mode +1.5%
Very Low Quiescent Current: Typ. 10uA
Very High Efficiency: Max >93%, and 54%
at 20uA output with V
IN
=2.3V and
V
OUT
=1.8V
Low Dropout operation: 100% Duty Cycle
Soft Start
Under-voltage Lockout
Thermal Protection
Available package: DFN6 2.0×1.8
Pin Configurations
Top View
UM3521DA
DFN6 2.0×1.8
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UM3521DA
Ordering Information
Part Number
UM3521DA
Packaging Type
DFN6
Marking Code
ADA
Shipping Qty
3000pcs/7Inch
Tape & Reel
Pin Description
Pin
Number
1
2
3
4
5
6
Symbol
SW
MODE
FB
EN
VIN
GND
Function
Switching Pin
Mode Select Pin. This pin is used to put the UM3521DA into fixed
frequency PWM mode by pulling MODE pin high.
Pin for Feedback Voltage
Enable Pin (Active with “H”)
Power Supply Pin
Ground Pin
Absolute Maximum Ratings
Symbol
V
IN
V
FB
V
EN
V
MODE
V
SW
T
O
T
STG
Input Voltage
FB Voltage
EN Voltage
MODE Voltage
SW Voltage
Operating Temperature
Storage Temperature Range
Parameter
Value
-0.3 to +6.0
-0.3 to V
IN
+0.3
-0.3 to V
IN
+0.3
-0.3 to V
IN
+0.3
-0.3 to V
IN
+0.3
-40 to +85
-65 to +150
Unit
V
V
V
V
V
°C
°C
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UM3521DA
Electrical Characteristics
(V
IN
=V
EN
=3.6V, V
OUT
=1.8V, V
MODE
=GND, T
A
=+25℃, unless otherwise noted)
Symbol
Parameter
Test Conditions
Min
Typ
V
IN
Input Voltage Range
2.0
I
Q
I
SHDN
Quiescent Current
Shutdown Current
V
IN
=3.6V,
V
MODE
=GND
V
EN
=GND
V
MODE
=V
IN
,
(PWM mode),
I
O
=10mA
V
MODE
=GND,
(PFM mode),
I
O
=10mA
10
0.1
1.773
1.800
3
600
2.00
V
IN
=3.6V,
I
SW
=100mA
V
IN
=3.6,
I
SW
= -100mA
2.25
0.28
0.18
1.0
V
IN
-0.3
GND+
0.3
1
2.50
Max
5.5
17
1.0
1.827
Unit
V
μA
μA
V
%
mA
MHz
Ω
Ω
A
V
V
μA
V
V
FB
Regulated Feedback
Voltage
I
O(Max)
f
R
DS(ON)
I
SW
V
ENH
V
ENL
I
EN
V
MODEH
V
MODEL
I
MODE
UVLO
Hys
sst
Maximum Output
Current
Oscillator Frequency
R
DS(ON)
of
P-CH MOSFET
R
DS(ON)
of
N-CH MOSFET
High Side Switch
Current Limit
EN Pin
High-Level
Threshold
EN Pin
Low-Level Threshold
EN Pin Input Current
MODE Pin
High-Level
Threshold
MODE Pin
Low-Level
Threshold
MODE Pin
Input Current
UVLO Detection
Voltage
UVLO hystersis
voltage
Soft Start Time
Output Voltage
Temperature
characteristics
Thermal Shutdown
Temp
V
EN
=5.5V
V
IN
-0.3
0.01
GND+
0.3
V
MODE
=5.5V
0.01
1.7
0.1
V
EN
=0V to V
IN
-40℃≤T
A
≤+85℃
0.15
0.3
±100
140
1
1.8
0.2
0.6
V
μA
V
V
ms
ppm/
℃
ºC
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UM3521DA
Typical Application Circuit
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UM3521DA
Typical Operating Characteristics
(MODE=0, L=2.2μH, V
OUT
=1.8V, unless otherwise noted.)
Efficiency vs Output Current
100%
90%
Output Voltage(V)
1.89
1.87
1.85
1.83
1.81
1.79
1.77
1.75
Output Voltage vs Output Current
Efficiency(%)
80%
70%
60%
50%
40%
30%
20%
10%
0%
1
10
100
1000
Output Current(mA)
VIN=2.3V
VIN=5.0V
VIN=2.3V
VIN=5.0V
0
100 200
300
400 500
600 700
800
Output Current(mA)
Quiescent Current vs Input Voltage
20
Quiescent Current(uA)
18
16
14
12
10
8
2
3
4
Input Voltage(V)
5
6
Output Voltage vs Input Voltage
1.9
EN=VIN,
Device not switching
Output Voltage(V)
Iout=300mA
1.85
1.8
1.75
1.7
0
1
2
3
4
5
Input Voltage(V)
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