General Description
The AAT2505 is a member of AnalogicTech's Total
Power Management ICTM (TPMICTM) product fam-
ily. It is a low dropout (LDO) linear regulator and a
step-down converter with an input voltage range of
2.7V to 5.5V, making it ideal for applications with
single cell lithium-ion / polymer batteries.
The LDO has an independent input pin and is capa-
ble of delivering up to 300mA of current. The linear
regulator has been designed for high-speed turn-on
and turn-off performance, fast transient response,
and good power supply rejection ratio (PSRR).
Other features include low quiescent current, low
dropout voltage, and a Power-OK (POK) open drain
output signaling when V
OUT
is in regulation.
The 600mA step-down converter is designed to
operate with 1.4MHz of switching frequency, mini-
mizing external component size and cost while
maintaining a low 27A no load quiescent current.
Peak current mode control with internal compen-
sation provides a stable converter with a low equiv-
alent series resistance (ESR) ceramic output
capacitor for extremely low output ripple.
For maximum battery life with high voltage outputs,
the step-down converter duty cycle increases to
100%. The output voltage is either fixed or adjustable
with an integrated P- and N-channel MOSFET power
stage and 1.4MHz switching frequency.
The AAT2505 is available in a Pb-free, 12-pin
TDFN33 package and is rated over a temperature
range of -40C to +85C.
Features
V
IN
Range: 2.7V to 5.5V
300mA LDO
-- 400mV Dropout Voltage at 300mA
-- High Accuracy: 1.5%
-- Fast Line / Load Transient Response
-- Power OK Output
600mA Step-Down Converter
-- Up To 98% Efficiency
-- 27A No Load Quiescent Current
-- Shutdown Current <1A
-- Low R
DS(ON)
Integrated Power Switches
-- Fast Turn-On Time (150s Typical)
-- Low Dropout 100% Duty Cycle
-- 1.4MHz Switching Frequency
-- Internal Soft Start
Over-Temperature and Current Limit
Protection
TDFN33-12 Package
-40C to +85C Temperature Range
Applications
Cellular Phones
Digital Cameras
Handheld Instruments
Microprocessor/DSP Core/IO Power
PDAs and Handheld Computers
Portable Media Players
AAT2505
Dual Channel, Step-Down
Converter/Linear Regulator
Typical Application
Efficiency
(V
OUT
= 2.5V; L = 6.8H)
Output Current (mA)
Efficiency (%)
60
70
80
90
100
0.1
1
10
100
1000
V
IN
= 3.3V
6.8H
L1
C1
4.7F
2.2F
C4
10F
C3
R3 100k
PGND
1
LX
2
VP
3
VCC
4
ENLDO
9
EN
10
FB
11
SGND
12
VLDO
5
OUT
6
GND
8
POK
7
AAT2505
U1
L1 Sumida CDRH3D16-4R7
C1 Murata GRM219R61A475KE19
C3 Murata GRM21BR60J106KE19
V
IN
= 2.7V to 5.5V
3.3V at 300mA
2.5V at 600mA
2505.2006.06.1.1
1
SystemPower
TM
Pin Descriptions
Pin Configuration
TDFN33-12
(Top View)
PGND
LX
VP
1
VCC
VLDO
OUT
SGND
FB
EN
ENLDO
GND
POK
2
3
4
5
6
12
11
10
9
8
7
Pin #
Symbol
Function
1
PGND
Step-down converter power ground return pin. Connect to the output and input capacitor
return. See section on PCB layout guidelines and evaluation board layout diagram.
2
LX
Power switching node. Output switching node that connects to the output inductor.
3
VP
Step-down converter power stage supply voltage. Must be closely decoupled to PGND.
4
VCC
Step-down converter bias supply. Connect to VP.
5
VLDO
LDO input voltage; should be decoupled with 1F or greater capacitor.
6
OUT
300mA LDO output pin. A 2.2F or greater output low-ESR ceramic capacitor is required
for stability.
7
POK
Power-OK output for the LDO. This open drain output is low when the OUT is out of regu-
lation. Connect a pull-up resistor from POK to OUT or VLDO. When LDO is in shutdown
(ENLDO = 0V), POK is pulled low.
8
GND
LDO ground connection pin.
9
ENLDO
Enable pin for LDO. When connected low, LDO is disabled and consumes less than 1A
of current.
10
EN
Step-down converter enable. When connected low, the step-down converter is disabled
and consumes less than 1A.
11
FB
Step-down converter feedback input pin. For fixed output voltage versions, this pin is con-
nected to the converter output, forcing the converter to regulate to the specific voltage.
For adjustable output versions, an external resistive divider ties to this point and programs
the output voltage to the desired value.
12
SGND
Step-down converter signal ground. For external feedback, return the feedback resistive
divider to this ground. For internal fixed version, tie to the point of load return. See sec-
tion on PCB layout guidelines and evaluation board layout diagram.
EP
Exposed paddle (bottom). Use properly sized vias for thermal coupling to the ground
plane. See section on PCB layout guidelines.
AAT2505
Dual Channel, Step-Down
Converter/Linear Regulator
2
2505.2006.06.1.1
Absolute Maximum Ratings
1
Thermal Information
Symbol
Description
Value
Units
P
D
Maximum Power Dissipation
2.0
W
JA
Thermal Resistance
2
50
C/W
Symbol
Description
Value
Units
V
P
, V
LDO
Input Voltages to GND
6.0
V
V
LX
Lx to GND
-0.3 to V
P
+ 0.3
V
V
FB
FB to GND
-0.3 to V
P
+ 0.3
V
V
EN
EN to GND
-0.3 to 6.0
V
T
J
Operating Junction Temperature Range
-40 to 150
C
T
LEAD
Maximum Soldering Temperature (at leads, 10 sec)
300
C
AAT2505
Dual Channel, Step-Down
Converter/Linear Regulator
2505.2006.06.1.1
3
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 with exposed paddle connected to ground plane.
Electrical Characteristics
1
V
IN
= V
LDO
= V
OUT(NOM)
+ 1V for V
OUT
options greater than 1.5V. V
IN
= V
LDO
= 2.5V for V
OUT
1.5V. I
OUT
= 1mA,
C
OUT
= 2.2F, C
IN
= 1F, T
A
= -40C to +85C, unless otherwise noted. Typical values are T
A
= 25C.
Symbol
Description
Conditions
Min
Typ Max
Units
LDO
V
OUT
Output Voltage Tolerance
I
OUT
= 1mA T
A
= 25C
-1.5
1.5
%
to 300mA T
A
= -40C to +85C
-2.5
2.5
V
IN
Input Voltage
V
OUT
+
5.5
V
V
DO
2
V
DO
Dropout Voltage
3, 4
I
OUT
= 300mA
400
600
mV
V
OUT
/
Line Regulation
V
IN
= V
OUT
+ 1V to 5V
0.09
%/V
V
OUT
* V
IN
V
OUT(Line)
Dynamic Line Regulation
I
OUT
= 300mA, V
IN
= V
OUT
+ 1V
2.5
mV
to V
OUT
+ 2V, T
R
/T
F
= 2s
V
OUT(Load)
Dynamic Load Regulation
I
OUT
= 1mA to 300mA, T
R
<5s
60
mV
I
OUT
Output Current
V
OUT
> 1.3V
300
mA
I
SC
Short-Circuit Current
V
OUT
< 0.4V
1
A
I
QLDO
LDO Quiescent Current
V
IN
= 5V, No Load, ENLDO = V
IN
70
125
A
V
POK
POK Trip Threshold
V
OUT
Rising, T
A
= 25C
90
94
98
% of V
OUT
V
POKHYS
POK Hysteresis
1.0
% of V
OUT
V
POK(OL)
POK Output Voltage Low
I
SINK
= 1mA
0.4
V
I
POK
POK Output Leakage Current
V
POK
< 5.5V, V
OUT
in Regulation
1.0
A
I
SHDN
Shutdown Current
V
IN
= 5V; ENLDO = GND,
1.0
A
EN = SGND = PGND
I
OUT
= 10mA
1kHz
65
PSRR
Power Supply Rejection Ratio
10kHz
45
dB
1MHz
42
T
SD
Over-Temperature Shutdown
145
C
Threshold
T
HYS
Over-Temperature Shutdown
15
C
Hysteresis
e
N
Output Noise
250
V
RMS
T
C
Output Voltage Temperature
22
ppm/C
Coefficient
AAT2505
Dual Channel, Step-Down
Converter/Linear Regulator
4
2505.2006.06.1.1
1. The AAT2505 is guaranteed to meet performance specifications over the -40C to +85C operating temperature range and is assured
by design, characterization, and correlation with statistical process controls.
2. To calculate the minimum LDO input voltage, use the following equation: V
IN(MIN)
= V
OUT(MAX)
+ V
DO(MAX)
, as long as V
IN
2.5V.
3. For V
OUT
< 2.1V, V
DO
= 2.5 - V
OUT
.
4. V
DO
is defined as V
IN
- V
OUT
when V
OUT
is 98% of nominal.
Electrical Characteristics
1
I
OUT
= 600mA; typical values are T
A
= 25C, V
IN
= V
CC
= V
P
= 3.6V.
Symbol
Description
Conditions
Min
Typ
Max Units
Buck Converter
V
IN
Input Voltage
2.7
5.5
V
V
IN
Rising
2.7
V
V
UVLO
UVLO Threshold
Hysteresis
100
mV
V
IN
Falling
1.8
V
V
OUT
Output Voltage Tolerance
I
OUT
= 0 to 600mA,
-3.0
3.0
%
V
IN
= 2.7V to 5.5V
V
OUT
Output Voltage Range
0.6
V
IN
V
I
QBUCK
Step-Down Converter
ENLDO = GND, No Load,
27
70
A
Quiescent Current
0.6V Adjustable Version
I
SHDN
Shutdown Current
EN = SGND = PGND,
1.0
A
ENLDO = GND
I
LIM
P-Channel Current Limit
800
mA
R
DS(ON)H
High Side Switch On Resistance
0.45
R
DS(ON)L
Low Side Switch On Resistance
0.40
I
LXLK
LX Leakage Current
V
IN
= 5.5V, V
LX
= 0 to V
IN
,
1.0
A
EN = SGND = PGND
V
Linereg
Line Regulation
V
IN
= 2.7V to 5.5V
0.1
%/V
V
FB
FB Threshold Voltage Accuracy
0.6V Output, No Load,
591
600
609
mV
T
A
= 25C
I
FB
FB Leakage Current
0.6V Output
0.2
A
R
FB
FB Impedance
> 0.6V Output
250
k
T
S
Start-Up Time
From Enable to Output
150
s
Regulation
F
OSC
Oscillator Frequency
T
A
= 25C
1.0
1.4
2.0
MHz
T
SD
Over-Temperature Shutdown
140
C
Threshold
T
HYS
Over-Temperature Shutdown
15
C
Hysteresis
Logic Signals
V
EN(L)
Enable Threshold Low
0.6
V
V
EN(H)
Enable Threshold High
1.4
V
I
EN(H)
Leakage Current
-1.0
1.0
A
AAT2505
Dual Channel, Step-Down
Converter/Linear Regulator
2505.2006.06.1.1
5
1. The AAT2505 is guaranteed to meet performance specifications over the -40C to +85C operating temperature range and is assured
by design, characterization, and correlation with statistical process controls.
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