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PDF WD1012EA-5 Data sheet ( Hoja de datos )
| Número de pieza | WD1012EA-5 | |
| Descripción | 600mA Synchronous Step-Down Regulator | |
| Fabricantes | WillSEMI | |
| Logotipo |  |
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WD1012EA-5/TR
1.5MHz, 600mA Synchronous Step-Down Regulator in SOT
General Description
The WD1012EA is a high efficiency monolithic synchronous buck
regulator using a constant frequency, current mode architecture.
The 2.7V to 5.5V input voltage range makes the WD1012EA ideally
suited for single Li-Ion battery-powered applications. Supply
current with no load is 22ȝA, dropping to <1ȝA in shut-
down. PWM (Pulse Width Modulation) operation provides very low
output ripple voltage for noise sensitive applications. 100% duty
cycle capability provides low dropout operation, extending battery
life in portable systems.
The switching frequency is internally set at 1.5MHz, allowing the
use of tiny surface mount inductors and capacitors. Low output
voltages are easily supported with the 0.6V feedback reference
voltage. The WD1012EA is available in SOT23 package. The
internal synchronous switch increases efficiency and eliminates
the need for an external Schottky diode.
Ordering Information
Top View
ORDER PART
NUMBER
WD1012EA-5/TR
PART MARKING
WD12
YYWW
Typical Application Circuit
Features
Ƶ 600mA Output Current
Ƶ High Efficiency: Up to 95%
Ƶ Tiny 5-Pin SOT23 Package
Ƶ 1.5MHz Constant Frequency Operation
Ƶ 2.7V to 5.5V Input Voltage Range
Ƶ Low Dropout Operation: 100% Duty Cycle
Ƶ Low Quiescent Current: Only 22ȝA During Operation
Ƶ Shutdown Mode Draws < 1ȝA Supply Current
Ƶ No Schottky Diode Required
Ƶ 0.6V Reference Allows Low Output Voltages
Ƶ Overtemperature Protected
Ƶ Adjustable Output Voltage.
Ƶ Current Mode Operation for Excellent Line and Load Transient
Response
Applications
Ƶ Cellular Telephones
Ƶ Personal Information Appliances
Ƶ Wireless and DSL Modems
Ƶ Digital Still Cameras
Ƶ MP3 Players
Ƶ Portable Instruments
Marking Information
Device
Package
WD1012EA-5/TR SOT23-5
Shipping
3000/Tape&Reel
For marking information, contact our sales representative directly
or through a willsemi distributor located in your area, otherwise
visit our website for detail.
1.2V
http://www.willsemi.com
330K
330K
Figure 1. High Efficient Step-Down Converter
Page 1
J a n . 2012 Rev3.0
1 page  
Function Diagram
WD1012EA-5/TR
Theory of Operation
PWM Control Mode
The WD1012EA step-down converter operates with
typically 1.5MHz fixed-frequency pulse width
modulation (PWM) at moderate to heavy load currents.
Both the main (P-channel MOSFET) and synchronous
(N-channel MOSFET) switches are internal. During
PWM operation, the converter uses a current-mode
control scheme to achieve good line and load regulation.
At the beginning of each clock cycle initiated by the
clock signal, the main switch is turned on. The current
flows from the input capacitor via the main switch
through the inductor to the output capacitor and load.
During this phase, the current ramps up until the PWM
comparator trips and the control logic turns off the
switch. After a dead time, which prevents shoot-through
current, the synchronous switch is turned on and the
inductor current ramps down. The current flows from
the inductor to the output capacitor and to the load. It
returns back to the inductor through the synchronous
switch.
The next cycle is initiated by the clock signal again
turning off the synchronous switch and turning on the
main switch.
Pulse Skipping Mode (PSM)
At light loads, the inductor current may reach zero or
reverse on each pulse. The synchronous switch is turned
off by the current reversal comparator, IRCMP, and the
switch voltage will ring. This is discontinuous mode
operation, and is normal behavior for the switching
regulator. At very light loads, the WD1012EA will
automatically skip pulses in pulse skipping mode (PSM)
operation to maintain output regulation.
Short-Circuit Protection
When the output is shorted to ground, the frequency of
the oscillator is reduced to about 280KHz. This
frequency foldback ensures that the inductor current has
more time to decay, thereby preventing runaway. The
oscillator’s frequency will progressively increase to
1.5MHz when VFB rises above 0V.
http://www.willsemi.com
Page 5
J a n . 2012 Rev3.0
5 Page | ||
| Páginas | Total 9 Páginas | |
| PDF Descargar | [ Datasheet WD1012EA-5.PDF ] | |
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