AAT2500
1MHz Step-Down Converter/LDO Regulator
2500.2005.08.1.9
1
SysPwr
TM
Typical Application
AAT2500 Step-Down Converter Efficiency
Load Current (mA)
Efficiency (%)
60
65
70
75
80
85
90
95
100
0.1
1
10
100
1000
V
IN
= 3.3V
1.8V
2.5V
4.7
H
L1
4.7
F
C1
2.2
F
C4
10
F
C3
10nF
C5
PGND
1
LX
2
VP
3
VCC
4
ENLDO
9
EN
10
FB
11
SGND
12
VLDO
5
OUT
6
GND
8
BYP
7
AAT2500
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 400mA
General Description
The AAT2500 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 lithium-ion/polymer batteries.
The LDO has an independent input and is capable
of delivering up to 300mA. 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 fea-
tures include low quiescent current and a low
dropout voltage.
The 400mA step-down converter is designed to
minimize external component size and cost while
maintaining a low 25A 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, the step-down converter
increases to 100% duty cycle and has a typical
180mV dropout voltage at 400mA. The output volt-
age is either fixed or adjustable with an integrated
P- and N-channel MOSFET power stage and
1MHz switching frequency.
The AAT2500 is available in a 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 Current Output
400mV LDO Dropout Voltage at 300mA
High Output Accuracy: 1.5%
Fast LDO Line / Load Transient Response
400mA, 96% Efficiency Step-Down Converter
25A No Load Quiescent Current for Step-
Down Converter
Shutdown Current <1A
Low R
DS(ON)
0.4
Integrated Power Switches
Low Dropout 100% Duty Cycle
1MHz Switching Frequency
Internal Soft Start
Over-Temperature Protection
Current Limit Protection
Available in 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
AAT2500
1MHz Step-Down Converter/LDO Regulator
2
2500.2005.08.1.9
Pin Descriptions
Pin Configuration
TDFN33-12
(TopView)
PGND
LX
VP
1
VCC
VLDO
OUT
SGND
FB
EN
ENLDO
GND
BYP
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 capaci-
tor 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
BYP
Bypass capacitor for the LDO. To improve AC ripple rejection, connect a 10nF capaci-
tor to GND. This will also provide a soft-start function.
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, LDO is disabled and consumes
less than 1A.
11
FB
Step-down converter feedback input pin. For fixed output voltage versions, this pin is
connected to the converter output, forcing the converter to regulate to the specific volt-
age. 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 resis-
tive divider to this ground. For internal fixed version, tie to the point of load return. See
section 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.
AAT2500
1MHz Step-Down Converter/LDO Regulator
2500.2005.08.1.9
3
Absolute Maximum Ratings
1
Thermal Information
Symbol
Description
Value
Units
P
D
Maximum Power Dissipation
2
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
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at
conditions 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.
AAT2500
1MHz Step-Down Converter/LDO Regulator
4
2500.2005.08.1.9
Electrical Characteristics
1
Symbol
Description
Conditions
Min
Typ Max
Units
LDO
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.
T
A
= 25C
-1.5
1.5
V
OUT
Output Voltage Tolerance
I
OUT
= 1mA to 300mA T
A
= -40C
-2.5
2.5
%
to 85C
V
IN
Input Voltage
V
OUT
+V
DO
2
5.5
V
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 to
2.5
mV
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
600
mA
I
QLDO
LDO Quiescent Current
V
IN
= 5V, No Load, ENLDO = V
IN
70
125
A
I
SHDN
Shutdown Current
V
IN
= 5V; ENLDO = GND,
1.0
A
EN = SGND = PGND
1kHz
67
PSRR
Power Supply Rejection Ratio I
OUT
= 10mA, C
BYP
= 10nF 10kHz
47
dB
1MHz
45
T
SD
Over-Temperature Shutdown
145
C
Threshold
T
HYS
Over-Temperature Shutdown
12
C
Hysteresis
e
N
Output Noise
e
NBW
= 300Hz to 50kHz
50
V
RMS
T
C
Output Voltage Temperature
22
ppm/C
Coefficient
1. The AAT2500 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.
AAT2500
1MHz Step-Down Converter/LDO Regulator
2500.2005.08.1.9
5
Electrical Characteristics
1
Symbol
Description
Conditions
Min
Typ Max
Units
Buck Converter Typical values are T
A
= 25C, V
IN
= V
CC
= V
p
= 3.6V.
V
IN
Input Voltage
2.7
5.5
V
V
IN
Rising
2.6
V
V
UVLO
UVLO Threshold
Hysteresis
100
mV
V
IN
Falling
1.8
V
V
OUT
Output Voltage Tolerance
I
OUT
= 0 to 400mA,
-3.0
+3.0
%
V
IN
= 2.7V to 5.5V
V
OUT
Output Voltage Range
Fixed Output Version
0.6
4.0
V
Adjustable Output Version
2
0.6
2.5
I
QBUCK
Step-Down Converter
ENLDO = GND, No Load,
25
50
A
Quiescent Current
0.6V Adjustable Model
I
SHDN
Shutdown Current
EN = SGND = PGND, ENLDO = GND
1.0
A
I
LIM
P-Channel Current Limit
600
mA
R
DS(ON)H
High Side Switch On
0.45
Resistance
R
DS(ON)L
Low Side Switch On
0.4
Resistance
I
LXLK
LX Leakage Current
V
IN
= 5.5V, V
LX
= 0 - V
IN
1.0
A
EN = SGND = PGND
I
LXLK, R
LX Reverse Leakage Current V
IN
= Open, V
LX
= 5.5V,
1.0
A
(fixed)
EN = SGND = PGND
V
Linereg
Line Regulation
V
IN
= 2.7V to 5.5V
0.2
%/V
V
FB
FB Threshold Voltage
0.6V Output, No Load, T
A
= 25C
597
600
615
mV
Accuracy
I
FB
FB Leakage Current
0.6V Output
0.2
A
R
FB
FB Impedance
>0.6V Output
250
k
F
OSC
Oscillator Frequency
T
A
= 25C
0.7
1.0
1.5
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
1.5
V
I
EN(H)
Leakage Current
1.0
1.0
A
1. The AAT2500 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. For adjustable version with higher than 2.5V output, please consult your AnalogicTech representative.
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