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PDF A7121 Data sheet ( Hoja de datos )
| Número de pieza | A7121 | |
| Descripción | 2A 1.2MHz HIGH EFFICIENCY SYNCHRONOUS STEP-DOWN DC-DC CONVERTER | |
| Fabricantes | AiT Semiconductor | |
| Logotipo |  |
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AiT Semiconductor Inc.
www.ait-ic.com
A7121
2A 1.2MHz HIGH EFFICIENCY
SYNCHRONOUS STEP-DOWN DC-DC CONVERTER
DESCRIPTION
FEATURES
The A7121 is a 1.2MHz constant frequency current
mode PWM step-down converter. It is ideal for portable
equipment requiring very high current up to 2A from
single-cell Lithium-ion batteries while still achieving over
90% efficiency during peak load conditions.
The A7121 also can run at 100% duty cycle for low
Input Voltage Range: 2.5V to 6.0V
Output Voltages from 0.6V to VIN
2A Output Current
High Efficiency: Up to 95%
1.2MHz Constant Switching Frequency
Low RDS(ON) Internal Switches: 0.15Ω
Allows Use of Ceramic Capacitors
dropout operation, extending battery life in portable
systems while light load operation provides very low
output ripple for noise sensitive applications.
The A7121 can supply up to 2A output load current from
a 2.5V to 6.0V input voltage and the output voltage can
be regulated as low as 0.6V. The high switching
frequency minimizes the size of external components
Current Mode Operation for Excellent Line
and Load Transient Response
Short-Circuit and Thermal Fault Protection
Soft Start
Low Dropout Operation: 100% Duty Cycle
Low Shutdown Current : ISHUTDOWN < 1μA
-40℃ to +85℃ Temperature Range
Available in DFN10 and MSOP10 Packages.
while keeping switching losses low. The internal slope
compensation setting allows the device to operate with
smaller inductor values to optimize size and provide
efficient operation.
The A7121 is available in DFN10 (3x3mm) and MSOP10
package.
APPLICATIONS
Cellular Phones
Digital Cameras
DSP Core Supplies
Printer
Portable Instruments
ORDERING INFORMATION
xDSL
MID or UMPC
Package Type
Part Number
DFN10
J10
A7121J10R-XX
A7121J10VR-XX
MSOP10
A7121MS10R-XX
MS10
A7121MS10VR-XX
Note
XX: 18=1.8V, ADJ=Adjustable
V: Green Package
R : Tape & Reel
AiT provides all Pb free products
Suffix “ V “ means Green Package
TYPICAL APPLICATION
REV1.0 -FEB 2010 RELEASED -
-1-
1 page  
AiT Semiconductor Inc.
www.ait-ic.com
A7121
2A 1.2MHz HIGH EFFICIENCY
SYNCHRONOUS STEP-DOWN DC-DC CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS
1. Efficiency vs. Output Current
VOUT =3.3V,TA = 25℃, L=2.2μH, CIN = COUT = 22μF
2. DC Regulation
VOUT =3.3V,TA = 25℃, L=2.2μH, CIN = COUT = 22μF
3. Efficiency vs. Output Current
VOUT =1.8V,TA = 25℃, L=2.2μH, CIN = COUT = 22μF
4. DC Regulation
VOUT =1.8V,TA = 25℃, L=2.2μH, CIN = COUT = 22μF
5. Efficiency vs. Output Current
VOUT =1.2V,TA = 25℃, L=2.2μH, CIN = COUT = 22μF
6. DC Regulation
VOUT =1.2V,TA = 25℃, L=2.2μH, CIN = COUT = 22μF
REV1.0 -FEB 2010 RELEASED -
-5-
5 Page 
AiT Semiconductor Inc.
www.ait-ic.com
A7121
2A 1.2MHz HIGH EFFICIENCY
SYNCHRONOUS STEP-DOWN DC-DC CONVERTER
reference voltage is internally set to program the converter output voltage. For the adjustable output, the
error amplifier reference is fixed at 0.6V.
Soft Start / Enable
Soft start limits the current surge seen at the input and eliminates output voltage overshoot. The enable pin is
active high. When pulled low, the enable input (EN) forces the A7121 into a low-power, non-switching state.
The total input current during shutdown is less than 1µA
Current Limit and Over-Temperature Protection
For overload conditions, the peak input current is limited to 3.5A. To minimize power dissipation and
stresses under current limit and short-circuit conditions, switching is terminated after entering current limit
for a series of pulses. The termination lasts for seven consecutive clock cycles after a current limit has
been sensed during a series of four consecutive clock cycles. Thermal protection completely disables
switching when internal dissipation becomes excessive. The junction over temperature threshold is 170°C
with 10°C of hysteresis. Once an over temperature or over current fault conditions is removed, the output
voltage automatically recovers.
Dropout Operation
When the battery input voltage decreases near the value of the output voltage, the A7121 allows the main
switch to remain on for more than one switching cycle and increases the duty cycle until it reaches 100%.
The duty cycle D of a step-down converter is defined as:
Where TON is the main switch on time and FOSC is the oscillator frequency. The output voltage then is the
input voltage minus the voltage drop across the main switch and the inductor. At low input supply voltage,
the RDS(ON) of the P-channel MOSFET increases, and the efficiency of the converter decreases. Caution
must be exercised to ensure the heat dissipated does not exceed the maximum junction temperature of
the IC.
Maximum Load Current
The A7121 will operate with an input supply voltage as low as 2.5V, however, the maximum load current
decreases at lower input voltages due to a large IR drop on the main switch and synchronous rectifier.
The slope compensation signal reduces the peak inductor current as a function of the duty cycle to prevent
sub-harmonic oscillations at duty cycles greater than 50%. Conversely the current limit increases as the
duty cycle decreases.
REV1.0 -FEB 2010 RELEASED -
- 11 -
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet A7121.PDF ] | |
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