AAT2504
Adjustable 3-Channel Regulator
General Description
The AAT2504 is a three-channel regulator consist-
ing of a step-down converter with an input voltage
range of 2.7V to 5.5V plus two low dropout (LDO)
linear regulators. The two LDOs have an input volt-
age range of 1.8V to 5.5V, making them well-suited
for post regulating from the step-down converter.
The step-down converter optimizes power efficiency
throughout the load range. Pulling the MODE/SYNC
pin high enables "PWM Only" operation, maintaining
constant frequency and low output ripple across the
operating range. Alternatively, the converter may be
synchronized to an external clock to the MODE/
SYNC pin. The step-down converter delivers up to
800mA of output current. The switching frequency is
2MHz, minimizing the size of external components.
The two LDOs (LDOA/LDOB) have independent
inputs and are capable of delivering up to 300mA
each. A Power-OK (POK) function provides an open
drain output signal when LDOA is within regulation.
Both LDOs feature low quiescent current and a low
dropout voltage. The output voltages for both LDOs
are adjustable to as low as 0.6V. The linear regula-
tors have independent Enable pins. Typical no load
quiescent current is a low 80µA when the step-
down converter and LDOs are enabled.
The AAT2504 is available in a Pb-free 3x4mm
QFN34-20 package and is rated over the -40°C to
+85°C temperature range.
Features
•
SystemPower
™
•
•
•
•
•
•
800mA Buck Converter
— V
IN
Range: 2.7V to 5.5V
— V
OUT
Range: 0.9V to V
IN
, Adjustable
— High Efficiency: 95%
— 2MHz Switching Frequency
— Synchronizable to External Clock
— Internal Soft Start
Two 300mA Linear Regulators
— V
IN
Range: 1.8V to 5.5V
— Low Dropout Voltage
— High Output Accuracy: ±1.5%
Low Total Quiescent Current I
Q
(80μA)
Independent Enable Pins
Over-Temperature Protection
QFN34-20 Package
-40°C to +85°C Temperature Range
Applications
•
•
•
•
•
Cellular Phones
Digital Cameras
Handheld Instruments
Microprocessor/DSP Core/IO Power
PDAs and Handheld Computers
Typical Application
L
LX
AAT2504
V
IN
VIN
VLDOA
VLDOB
VP
MODE/SYNC
ENA
ENB
EN
V
OUT
(Step-down)
FB
OUTA
100kΩ
POK
FBA
OUTB
OUTB
POK
R
1
R
1A
OUTA
C
OUT
R
1B
FBB
R
2A
2.2μF
2.2μF
R
2
R
2B
PGND
AGND
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1
AAT2504
Adjustable 3-Channel Regulator
Pin Descriptions
Pin #
1
2
3
4
Symbol
FBB
ENA
ENB
MODE/SYNC
Function
Feedback input pin for LDOB. This pin is used to regulate the output of LDOB to the desired
value via an external resistor divider.
Enable pin for LDOA. Active high.
Enable pin for LDOB. Active high.
PWM operation and oscillator synchronization pin. Connect to ground for PWM/Light Load
operation and optimized efficiency throughout the load range. Connect high for low noise
PWM operation under all operating conditions. When connected to an external clock, the
internal oscillator is disabled and the step-down converter is synchronized to an external
clock applied to this pin (PWM only).
Feedback input pin for the step-down converter. This pin is used to see the output of the
converter to regulate to the desired value via an external resistor divider.
Ground connection pin.
Main power ground return pin for the step-down converter. Connect to the output and input
capacitor return.
Connect inductor to this pin. Switching node internally connected to the drain of both high-
and low-side MOSFETs.
Input supply voltage for the converter. Must be closely decoupled.
Not connected.
Bias supply. Supply power for the internal circuitry. Connect to input power via low pass filter
with decoupling to AGND.
Enable for the step-down converter. Active high.
Power-OK pin with open drain output. It is pulled low when the OUTA pin is outside the regu-
lation window. Place a pull-up resistor between POK and OUTA.
Feedback input pin for LDOA. This pin is used to regulate the output of LDOA to the desired
value via an external resistor divider.
LDOA output pin; should be closely decoupled with a low-ESR ceramic capacitor.
Input voltage pin for linear regulator A; should be closely decoupled.
Input voltage pin for linear regulator B; should be closely decoupled.
LDOB output pin; should be closely decoupled with a low-ESR ceramic capacitor.
Exposed paddle; connect to ground directly beneath the package.
5
6
7
8, 9
10
11, 12
13
14
15
16
17
18
19
20
EP
FB
AGND
PGND
LX
VP
N/C
VIN
EN
POK
FBA
OUTA
VLDOA
VLDOB
OUTB
2
2504.2007.06.1.0
AAT2504
Adjustable 3-Channel Regulator
Pin Configuration
QFN34-20
(Top View)
OUTA
VLDOA
VLDOB
OUTB
20
19
18
17
FBB
ENA
ENB
MODE/SYNC
FB
AGND
1
2
3
4
5
6
16
15
14
13
12
11
FBA
POK
EN
VIN
N/C
N/C
10
9
7
8
VP
LX
LX
PGND
Absolute Maximum Ratings
1
Symbol
V
P
, V
IN
, V
LDO
V
LX
V
FB
V
EN
T
J
T
LEAD
Description
Input Voltage and Bias Power to GND
LX to GND
FB to GND
EN and EN_LDO to GND
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
Value
6.0
-0.3 to V
P
+ 0.3
-0.3 to V
P
+ 0.3
-0.3 to 6.0
-40 to 150
300
Units
V
V
V
V
°C
°C
Thermal Information
Symbol
P
D
θ
JA
Description
Maximum Power Dissipation (T
A
= 25°C)
Thermal Resistance
2
Value
2.0
50
Units
W
°C/W
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at condi-
tions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Mounted on an FR4 board.
2504.2007.06.1.0
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AAT2504
Adjustable 3-Channel Regulator
Electrical Characteristics
1
V
IN
= 3.6V; T
A
= -40°C to +85°C, unless otherwise noted. Typical values are T
A
= 25°C.
Symbol
Description
Conditions
ENA = ENB = EN = V
IN
; I
LOAD
= 0
ENA = ENB = EN = GND
V
IN
Rising
Hysteresis
V
IN
Falling
Min Typ Max
80
145
1.0
2.2
Units
µA
µA
V
mV
V
V
%
V
mV
%/V
V
V
mA
µA
°C
°C
Bias Power Supply
I
Q
Quiescent Current
I
SHDN
Shutdown Current
UVLO
Under-Voltage Lockout Voltage
250
1.7
1.8
5.5
-1.5
1.5
-2.5
2.5
0.593 0.6 0.607
300
0.09
0.6
1.4
300
1.0
140
15
80
90
1.0
98
0.4
1.0
LDOA, LDOB
V
LDO
Input Voltage
V
OUT
V
FB
V
DO
Output Voltage Tolerance
Feedback Voltage
Dropout Voltage
2, 3
Line Regulation
4
Enable Threshold Low
Enable Threshold High
Output Current
Shutdown Current
Over-Temperature Shutdown
Threshold
Over-Temperature Shutdown
Hysteresis
I
OUT
= 1mA
to 300mA
I
OUT
= 300mA
V
IN
= V
OUT
+ 1 to 5.0V
T
A
= 25°C
T
A
= -40°C to +85°C
ΔV
LINEREG
/
V
IN
V
EN(L)
V
EN(H)
I
OUT
I
SHT
T
SD
T
HYS
LDOA
V
POK
V
POKHYS
V
POK(LO)
I
POK
V
LDO (MIN)
= 2.5
V
IN
= 5V
Power-OK Trip Threshold
V
OUT
Rising, T
A
= 25°C
Power-OK Hysteresis
Power-OK Output Voltage Low
I
SINK
= 1mA
Power-OK Output Leakage Current V
POK
<5.5V, V
OUT
in Regulation
% of V
OUT
% of V
OUT
V
µA
1. The AAT2504 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured
by design, characterization, and correlation with statistical process controls.
2. V
DO
is defined as V
IN
- V
OUT
when V
OUT
is 98% of nominal.
3. For V
OUT
< 1.5V, V
DO
= 1.8 - V
OUT
.
4. C
IN
= 10µF.
4
2504.2007.06.1.0
AAT2504
Adjustable 3-Channel Regulator
Electrical Characteristics (continued)
1
V
IN
= 3.6V; T
A
= -40°C to +85°C, unless otherwise noted. Typical values are T
A
= 25°C.
Symbol
Description
Conditions
Min
2.7
I
OUT
= 0 to 800mA;
V
IN
= 2.7V to 5.5V
-3.0
0.9
0.891
EN = GND
V
IN
= 5.5, V
LX
= 0 - V
IN
V
FB
= 1.0V
280
160
I
LOAD
= 10 to 800mA
0.2
0.2
1.6
2.0
140
15
0.6
V
EN
= 5V, V
IN
= 5V
1.4
-1.0
1.0
2.4
Typ
Max
5.5
3.0
V
IN
0.909
1.0
1.0
0.2
1.2
Units
V
%
V
V
µA
µA
µA
A
mΩ
mΩ
%
%/V
MHz
°C
°C
V
V
µA
Step-Down Converter
V
IN
Input Voltage
V
OUT
V
OUT
V
FB
I
SHDN
I
LX_LEAK
I
FB
I
LIM
R
DS(ON)H
R
DS(ON)L
ΔV
LOADREG
/
V
OUT
ΔV
LINEREG
/
V
IN
F
OSC
T
SD
T
HYS
V
EN(L)
V
EN(H)
I
EN
Output Voltage Tolerance
V
OUT
Programmable Range
Feedback Threshold Voltage
Shutdown Current
LX Leakage Current
Feedback Leakage
Current Limit
High Side Switch On Resistance
Low Side Switch On Resistance
Load Regulation
Line Regulation
Oscillator Frequency
Over-Temperature Shutdown
Threshold
Over-Temperature Shutdown
Hysteresis
Enable Threshold Low
Enable Threshold High
EN Input Leakage
0.9
1. The AAT2504 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured
by design, characterization, and correlation with statistical process controls.
2504.2007.06.1.0
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