AAT2506
1MHz Step-Down Converter/LDO Regulator
General Description
The AAT2506 is a member of AnalogicTech's Total
Power Management IC™ (TPMIC™) 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 AAT2506 is available in either a fixed version
with internal feedback or a programmable version
with external feedback resistors. It can deliver
600mA of load current while maintaining a low
25µA no load quiescent current. The 1MHz switch-
ing frequency minimizes the size of external com-
ponents while keeping switching losses low. The
AAT2506 feedback and control delivers excellent
load regulation and transient response with a small
output inductor and capacitor.
The AAT2506 is designed to maintain high efficien-
cy throughout the operating range, which is critical
for portable applications.
The AAT2506 is available in a 12-pin TDFN33
package, and is rated over a temperature range of
-40°C to +85°C.
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
SysPwr
™
V
IN
Range: 2.7V to 5.5V
V
OUT
Range: 0.6V to V
IN
300mA LDO Current Output
400mV LDO Dropout Voltage at 300mA
High Output Accuracy: ±1.5%
Fast LDO Line / Load Transient Response
600mA, 97% Efficiency Step-Down Converter
Fast Turn-On Time (100µs Typical)
25µA No Load Quiescent Current for Step-
Down Converter
Shutdown Current <1µA
Low R
DS(ON)
0.4Ω Integrated Power Switches
100% Duty Cycle Low Dropout Operation
1MHz Switching Frequency
100µs Typical Soft Start
Over-Temperature Protection
Current Limit Protection
Available in TDFN33-12 Package
-40°C to +85°C Temperature Range
Applications
•
•
•
•
•
•
Cellular Phones
Digital Cameras
Handheld Instruments
Microprocessor/DSP Core/IO Power
PDAs and Handheld Computers
Portable Media Players
Typical Application
V
IN
= 2.7V to 5.5V
AAT2506 Step-Down Converter Efficiency
(V
OUT
= 2.5V; L = 10µH)
µ
VP
VLDO
ENLDO
OUT
BYP
GND
VCC
EN
LX
FB
SGND
PGND
4
10
C3
10µF
3
5
100
L1
4.7µH
6
7
8
11
12
1
Efficiency (%)
3.3V at 300mA
9
2
90
V
IN
= 3.3V
80
C4
2.2µF
C1
22µF
C5
10nF
U1
AAT2506
70
60
0.1
L1 Sumida CDRH3D16-4R7 C1 Murata GRM219R61A475KE19
C3 Murata GRM21BR60J106KE19
1
10
100
1000
Output Current (mA)
2506.2005.12.1.0
1
AAT2506
1MHz Step-Down Converter/LDO Regulator
Pin Descriptions
Pin #
1
2
3
4
5
6
7
8
9
10
11
Symbol
PGND
LX
VP
VCC
VLDO
OUT
BYP
GND
ENLDO
EN
FB
Function
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.
Power switching node. Output switching node that connects to the output inductor.
Step-down converter power stage supply voltage. Must be closely decoupled to PGND.
Step-down converter bias supply. Connect to VP.
LDO input voltage; should be decoupled with 1µF or greater capacitor.
300mA LDO output pin. A 2.2µF or greater output low-ESR ceramic capacitor is
required for stability.
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.
LDO ground connection pin.
Enable pin for LDO. When connected low, LDO is disabled and consumes less than
1µA of current.
Step-down converter enable. When connected low, LDO is disabled and consumes
less than 1µA.
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.
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.
Exposed paddle (bottom). Use properly sized vias for thermal coupling to the ground
plane. See section on PCB layout guidelines.
12
SGND
EP
Pin Configuration
TDFN33-12
(TopView)
PGND
LX
VP
VCC
VLDO
OUT
1
2
3
4
5
6
12
11
10
9
8
7
SGND
FB
EN
ENLDO
GND
BYP
2
2506.2005.12.1.0
AAT2506
1MHz Step-Down Converter/LDO Regulator
Absolute Maximum Ratings
1
Symbol
V
P
, V
LDO
V
LX
V
FB
V
EN
T
J
T
LEAD
Description
Input Voltages to GND
LX to GND
FB to GND
EN 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
Thermal Resistance
2
Value
2
50
Units
W
°C/W
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.
2506.2005.12.1.0
3
AAT2506
1MHz Step-Down Converter/LDO Regulator
Electrical Characteristics
1
Symbol
LDO
Description
Conditions
Min
Typ Max
Units
V
OUT
V
IN
V
DO
∆V
OUT
/
V
OUT
*∆V
IN
∆V
OUT(Line)
∆V
OUT(Load)
I
OUT
I
SC
I
QLDO
I
SHDN
PSRR
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
= 2.2µF, C
IN
= 1µF, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are T
A
= 25°C.
T
A
= 25°C
-1.5
1.5
Output Voltage Tolerance
I
OUT
= 1mA to 300mA T
A
= -40°C
%
-2.5
2.5
to 85°C
Input Voltage
V
OUT
+V
DO
2
5.5
V
Dropout Voltage
3, 4
I
OUT
= 300mA
400 600
mV
Line Regulation
Dynamic Line Regulation
Dynamic Load Regulation
Output Current
Short-Circuit Current
LDO Quiescent Current
Shutdown Current
V
IN
= V
OUT
+ 1V to 5V
I
OUT
= 300mA, V
IN
= V
OUT
+ 1V to
V
OUT
+ 2V, T
R
/T
F
= 2µS
I
OUT
= 1mA to 300mA, T
R
<5µS
V
OUT
> 1.3V
V
OUT
< 0.4V
V
IN
= 5V, No Load, ENLDO = V
IN
V
IN
= 5V; ENLDO = GND,
EN = SGND = PGND
1kHz
I
OUT
= 10mA, C
BYP
= 10nF 10kHz
1MHz
2.5
60
300
600
70
125
1.0
67
47
45
145
12
e
NBW
= 300Hz to 50kHz
50
22
0.09
%/V
mV
mV
mA
mA
µA
µA
Power Supply Rejection Ratio
Over-Temperature Shutdown
Threshold
Over-Temperature Shutdown
Hysteresis
Output Noise
Output Voltage Temperature
Coefficient
dB
T
SD
T
HYS
e
N
T
C
°C
°C
µV
RMS
ppm/°C
1. The AAT2506 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. 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.
4
2506.2005.12.1.0
AAT2506
1MHz Step-Down Converter/LDO Regulator
Electrical Characteristics
1
Symbol
Description
Conditions
Min
2.7
100
1.8
-3.5
0.6
25
+3.5
4.0
50
1.0
600
0.45
0.40
1.0
1.0
0.5
591
600
609
0.2
1.5
Typ
Max
5.5
2.6
Units
V
V
mV
V
%
V
µA
µA
mA
Ω
Ω
µA
µA
%/V
mV
µA
MHz
µs
°C
°C
Buck Converter
Typical values are T
A
= 25°C, V
IN
= V
CC
= V
p
= 3.6V.
V
IN
Input Voltage
V
IN
Rising
V
UVLO
UVLO Threshold
Hysteresis
V
IN
Falling
I
OUT
= 0 to 400mA,
V
OUT
Output Voltage Tolerance
V
IN
= 2.7V to 5.5V
V
OUT
Output Voltage Range
Fixed Output Version
Step-Down Converter
ENLDO = GND, No Load,
I
QBUCK
Quiescent Current
0.6V Adjustable Model
I
SHDN
Shutdown Current
EN = SGND = PGND, ENLDO = GND
I
LIM
P-Channel Current Limit
High Side Switch On
R
DS(ON)H
Resistance
Low Side Switch On
R
DS(ON)L
Resistance
V
IN
= 5.5V, V
LX
= 0 - V
IN
I
LXLK
LX Leakage Current
EN = SGND = PGND
I
LXLK, R
LX Reverse Leakage Current V
IN
= Open, V
LX
= 5.5V,
(fixed)
EN = SGND = PGND
V
Linereg
Line Regulation
V
IN
= 2.7V to 5.5V
FB Threshold Voltage
V
FB
0.6V Output, No Load, T
A
= 25°C
Accuracy
I
FB
FB Leakage Current
0.6V Output
F
OSC
Oscillator Frequency
T
A
= 25°C
T
S
Start-Up Time
From Enable to Output Regulation
Over-Temperature Shutdown
T
SD
Threshold
Over-Temperature Shutdown
T
HYS
Hysteresis
Logic Signals
V
EN(L)
Enable Threshold Low
V
EN(H)
Enable Threshold High
I
EN(H)
Leakage Current
0.7
1.0
100
140
15
0.6
1.5
1.0
1.0
V
V
µA
1. The AAT2506 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.
2506.2005.12.1.0
5
