WD3123E
WD3123E
1.2MHz, High Voltage, Boost Converter
Http//:www.sh-willsemi.com
Descriptions
The WD3123E is a current mode step up converter
intended for small, low
power
applications.The
SOT-23-6L
converter input voltage ranging from 2.6V to 5.5V. The
Output voltage can be set up to 27V. The frequency is
1.2MHz allows the use of small external inductors and
capacitors and provides fast transient response.
Internal soft start results in small inrush current and
extends battery life. Internal power MOSFET with very
low RDS (ON) provides high efficiency. The WD3123E
automatically transits from PWM to PFM during light
load condition further increasing efficiency. The
converter also provides protection functions such as
under-voltage lockout, current limit and thermal
shutdown. The WD3123E is available in 5-pin SOT-23
package.
SOT-23-5L
Features
Input voltage range
Switching frequency
Efficiency
: 2.6~5.5V
: 1.2MHz
: Up to 87%
Pin configuration (Top view)
Feedback reference voltage : 1.238 V
Adjustable output voltage range up to 27V
Shutdown Current
≤ 1uA
Applications
Cellphones
PADs
STBs
DSCs
3123 = Device code
YY
WW
= Year code
= Week code
Marking
Order information
Device
WD3123E-5/TR
Package
SOT-23-5L
Shipping
3000/Reel&Tape
Will Semiconductor Ltd.
1
Jan, 2014 - Rev. 1.1
WD3123E
Pin descriptions
Symbol
SW
GND
SOT-23-5L
1
2
Descriptions
Power Switch Output.
Ground
Feedback Input.
FB
3
FB voltage is 1.238V.
Connect a resistor divider to
FB.
Regulator
On/Off
Control
Input. A high input at EN turns
on the converter, and a low
EN
4
input turns it off. When not
used, connect EN to the input
source for automatic startup.
The EN pin cannot be left
floating.
FB
6
Output Feedback pin
Block diagram
Will Semiconductor Ltd.
2
Jan, 2014 - Rev. 1.1
WD3123E
Absolute maximum ratings
Parameter
VCC Pin Voltage
Feedback pin Voltage
EN Pin Voltage
Switch Pin Voltage
Power Dissipation
Storage temperature Range
Operation Temperature Range
Thermal Resistance from Junction to case
Thermal Resistance from Junction to ambient
Note:
θ
JA
is
Symbol
V
CC
V
FB
V
EN
V
SW
PD
T
ST
T
OP
θ
θ
JC
JA
Value
GND - 0.3 to GND + 6.5
GND - 0.3 to V
CC
+ 0.3
GND- 0.3 to V
CC
+ 0.3
30
(T
J
-T
A
)/θ
JA
Units
V
V
V
V
V
℃
℃
℃/W
℃/W
-40 to +150
-40 to +85
110
250
measured with the PCB copper area of approximately 1 in
2
(Multi-layer).
Electrical Characteristics
(V
CC
= 5V, V
OUT
= 12V, T
A
= 25℃. unless otherwise noted.)
PARAMETER
Input Voltage Range
Under Voltage Lockout
UVLO Hysteresis
Step-Up Voltage Adjust Range
Shutdown current
Operating quiescent current
Feedback Voltage
FB Input Leakage Current
Line Regulation
Load Regulation
Oscillation Frequency
Maximum Duty
N-channel MOSFET
current limit
MOSFET on-resistance
(Note 1)
SW Leakage Current
EN pin logic input threshold
voltage
EN Hysteresis
EN Pin Input Current
Thermal shutdown
Thermal shutdown Hysteresis
Note 1:
Guaranteed by design.
Will Semiconductor Ltd.
3
Jan, 2014 - Rev. 1.1
F
OSC
D
MAX
I
LIM
R
DS(ON)
I
SWL
V
ENL
V
ENH
hys
I
EN-LKG
T
DS
T
SH
V
EN
=GND or V
CC
1.0
200
0.01
150
35
1
Duty=50%
V
CC
=3V, I
SW
=1A
V
CC
=5V, I
SW
=1A
V
SW
= 27V, V
FB
=1.5V
Symbol
V
CC
U
VLO
V
CC(hys)
V
OUT
I
SD
I
CCQ
V
FB
I
FB-LKG
V
FB
= 1.3V
V
IN
=2.5V to 5.5V
I
OUT
= 20mA
V
IN
=5V
I
OUT
=1mA to 400mA
0.9
82
V
EN
= 0V
V
FB
=1.5V, I
OUT
=0mA,
1.213
-100
3
0.1
150
1.238
0.01
0.2
0.2
1.2
87
1.9
650
500
1
0.4
1.5
Rising
Test Condition
Min
2.6
2.35
-0.13
27
1
250
1.263
+100
Typ
Max
5.5
2.60
Units
V
V
V
V
uA
uA
V
nA
%/V
%
MHz
%
A
mΩ
uA
V
V
mV
uA
℃
℃
WD3123E
Application Circuit
V
IN
= 5V
C1
10uF
ON
OFF
C3
1nF
R4
1MΩ
L1
4.7uH
D1
WSB5508L
V
OUT
= 12V
C2
4.7uF
U1
5
4
VCC
EN
WD3123E
SW
FB
GND
1
3
R3
R2
470K
R1
54K
2
R2
V
OUT
½ 1.238V 1
R1
R2 Suggest 390K~820K
V
IN
2.6~3.6V
2.6~5.3V
2.6~5.5V
V
OUT
5V
7V
7.5~27V
R3
120KΩ
82KΩ
0Ω
Application Information
Setting the Output Voltage
Application circuit item shows the basic application circuit with WD3123E adjustable output version. The
external resistor sets the output voltage according to the following equation:
R1
V
out
½ 1.238V 1
R2
Table 1 Resistor select for output voltage setting
For most applications, R2 is a suggested a value by 390K~820KΩ. Place the resistor-divider as close to
the IC as possible to reduce the noise sensitivity.
Under Voltage Lockout (UVLO)
To avoid mis-operation of the device at low input voltages an under voltage lockout is included that
disables the device, if the input voltage falls below (2.35V-130mV).
Input Capacitor Selection
The input capacitor reduces the surge current drawn from the input and switching noise from the device.
The input capacitor impedance at the switching frequency shall be less than input source impedance to
Will Semiconductor Ltd.
4
Jan, 2014 - Rev. 1.1
WD3123E
prevent high frequency switching current passing to the input. A low ESR input capacitor sized for maximum
RMS current must be used. Ceramic capacitors with X5R or X7R dielectrics are highly recommended
because of their low ESR and small temperature coefficients. A 10µ ceramic capacitor for most applications
F
is sufficient. For a lower output power requirement application, this value can be decreased.
Output Capacitor Selection
The output capacitor is required to keep the output voltage ripple small and to ensure regulation loop
stability. The output capacitor must have low impedance at the switching frequency. Ceramic capacitors with
X5R or X7R dielectrics are recommended due to their low ESR and high ripple current. A 4.7uF ceramic
capacitors works for most of the applications. Higher capacitor values can be used to improve the load
transient response.
Layout Guide
Will Semiconductor Ltd.
5
Jan, 2014 - Rev. 1.1
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