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PDF AAT1112 Data sheet ( Hoja de datos )
| Número de pieza | AAT1112 | |
| Descripción | Step-Down Converter | |
| Fabricantes | Advanced Analog Technology | |
| Logotipo |  |
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General Description
The AAT1112 SwitchReg is a 1.5A step-down con-
verter with an input voltage range of 2.4V to 5.5V
and an adjustable output voltage from 0.6V to VIN.
The 1.4MHz switching frequency enables the use
of small external components. The small footprint
and high efficiency make the AAT1112 an ideal
choice for portable applications.
The AAT1112 delivers 1.5A maximum output current
while consuming only 42µA of no-load quiescent
current. Ultra-low RDS(ON) integrated MOSFETs and
100% duty cycle operation make the AAT1112 an
ideal choice for high output voltage, high current
applications which require a low dropout threshold.
The AAT1112 provides excellent transient
response and high output accuracy across the
operating range. No external compensation com-
ponents are required.
The AAT1112 is designed to maintain high efficien-
cy throughout the load range. Pulling the MODE/
SYNC pin high enables "PWM Only" mode, main-
taining constant frequency and low output ripple
across the operating range. Alternatively, the con-
verter may be synchronized to an external clock
input via the MODE/SYNC pin. Over-temperature
and short-circuit protection safeguard the AAT1112
and system components from damage.
The AAT1112 is available in a Pb-free, space-sav-
ing TDFN33-12 or 2.75x3mm TSOPJW-12 pack-
age. The product is rated over an operating tem-
perature range of -40°C to +85°C.
AAT1112
1.5A, 1.4MHz Step-Down Converter
Features
SwitchReg™
• 1.5A Maximum Output Current
• Input Voltage: 2.4V to 5.5V
• Output Voltage: 0.6V to VIN
• Up to 95% Efficiency
• 42µA No Load Quiescent Current
• No External Compensation Required
• 1.4MHz Switching Frequency
• Synchronizable to External Clock
• Optional "PWM Only" Low Noise Mode
• 100% Duty Cycle Low-Dropout Operation
• Internal Soft Start
• Over-Temperature and Current Limit
Protection
• <1µA Shutdown Current
• TSOPJW-12 or TDFN33-12 Package
• Temperature Range: -40°C to +85°C
Applications
• Cellular Phones
• Digital Cameras
• Hard Disk Drives
• MP3 Players
• PDAs and Handheld Computers
• Portable Media Players
• USB Devices
Typical Application
VIN
C2
10µF
VP LX
AAT1112
VIN
EN FB
MODE/SYNC
GND
PGND
L1
3.3µH
VOUT= 3.3V
R1
267kΩ
R2
59kΩ
C1
22µF
1112.2007.01.1.1
1
1 page  
AAT1112
1.5A, 1.4MHz Step-Down Converter
Typical Characteristics
Efficiency vs. Output Current
(PFM Mode; VOUT = 3.3V)
100
VIN = 3.6V
90
80 VIN = 4.2V VIN = 5.0V
70
60
50
40
0.1
1 10 100 1000
Output Current (mA)
10000
Load Regulation
(PFM Mode; VOUT = 3.3V)
0.50
0.25 VIN = 3.6V VIN = 4.2V
0.00
-0.25
VIN = 5.0V
-0.50
0.1
1 10 100 1000
Output Current (mA)
10000
Efficiency vs. Output Current
(PWM Mode; VOUT = 3.3V)
100
VIN = 3.6V
80
VIN = 5.0V
60
VIN = 4.2V
40
20
0
1.0 10 100 1000
Output Current (mA)
10000
0.50
0.25
0.00
-0.25
-0.50
0.1
Load Regulation
(PWM Mode; VOUT = 3.3V)
VIN = 3.6V
VIN = 5.0V
VIN = 4.2V
1 10 100 1000
Output Current (mA)
10000
Efficiency vs. Output Current
(PFM Mode; VOUT = 2.5V)
100
VIN = 2.7V
90
80 VIN = 3.6V VIN = 4.2V
70
60
50
0.1
1 10 100 1000
Output Current (mA)
10000
0.50
0.25
0.00
-0.25
-0.50
0.1
Load Regulation
(PFM Mode; VOUT = 2.5V)
VIN = 2.7V VIN = 3.6V
VIN = 4.2V
1 10 100 1000
Output Current (mA)
10000
1112.2007.01.1.1
5
5 Page 
AAT1112
1.5A, 1.4MHz Step-Down Converter
Output regulation is maintained until the dropout
voltage, or minimum input voltage, is reached. At
1.5A output load, dropout voltage headroom is
approximately 200mV.
The AAT1112 typically achieves better than ±0.5%
output regulation across the input voltage and output
load range. A current limit of 2.0A (typical) protects
the IC and system components from short-circuit
damage. Typical no load quiescent current is 42µA.
Thermal protection completely disables switching
when the maximum junction temperature is detect-
ed. The junction over-temperature threshold is
140°C with 15°C of hysteresis. Once an over-tem-
perature or over-current fault condition is removed,
the output voltage automatically recovers.
Peak current mode control and optimized internal
compensation provide high loop bandwidth and
excellent response to input voltage and fast load
transient events. Soft start eliminates output volt-
age overshoot when the enable or the input voltage
is applied. Under-voltage lockout prevents spuri-
ous start-up events.
Control Loop
The AAT1112 is a peak current mode step-down
converter. The current through the P-channel
MOSFET (high side) is sensed for current loop
control, as well as short-circuit and overload pro-
tection. A fixed slope compensation signal is added
to the sensed current to maintain stability for duty
cycles greater than 50%. The peak current mode
loop appears as a voltage-programmed current
source in parallel with the output capacitor.
The output of the voltage error amplifier programs
the current mode loop for the necessary peak switch
current to force a constant output voltage for all load
and line conditions. Internal loop compensation ter-
minates the transconductance voltage error amplifi-
er output. The reference voltage is internally set to
program the converter output voltage greater than or
equal to 0.6V.
Soft Start/Enable
Soft start limits the current surge seen at the input
and eliminates output voltage overshoot. When
pulled low, the enable input forces the AAT1112 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 minimize power dissipation and stresses
under current limit and short-circuit conditions,
switching is terminated after entering current limit
for a series of pulses. Switching is terminated for
seven consecutive clock cycles after a current limit
has been sensed for a series of four consecutive
clock cycles.
Thermal protection completely disables switching
when internal dissipation becomes excessive. The
junction over-temperature threshold is 140°C with
15°C of hysteresis. Once an over-temperature or
over-current fault conditions is removed, the output
voltage automatically recovers.
Under-Voltage Lockout
Internal bias of all circuits is controlled via the VIN
input. Under-voltage lockout (UVLO) guarantees
sufficient VIN bias and proper operation of all inter-
nal circuitry prior to activation.
1112.2007.01.1.1
11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet AAT1112.PDF ] | |
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