Advanced Analog Technology, Inc.
AAT1109A
Preliminary and Provisional
ONE-CHANNEL BOOST SWITCHING REGULATOR
Features
Under-voltage lockout protection
Totem pole output
Output short circuit protection
Incorporates soft start function
Wide operating frequency：
10kHz to 1MHz
Shut down control
Low dissipation current :
Typical 1.6mA in operation
Sop-8 & Tssop-8 package available
General Description
The AAT1109A is a one-channel switching
regulator control IC incorporating a soft start
function and a short circuit protection function.
Each device consists of an on-chip voltage reference,
error amplifier, pulse width modulation controller,
under-voltage protection, soft start and short circuit
protection circuits. Switching frequencies up to
1MHz are set by an external resistor and capacitor.
Soft-start time can be implemented by the SCP
capacitor.
Additionally, a chip enable feature is provided to
power down reducing the supply current to 10uA.
With a minimum number of external components,
the AAT1109A offers a simple and cost effective
solution.
Pin Configuration
TOP VIEW
-IN
SCP
Vcc
CE
1
2
3
4
8
7
6
5
FB
OSC
GND
OUT
(SOP-8 PACKAGE)
(TSSOP-8 PACKAGE)
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AAT1109A
Pin Description
Pin #
1
2
3
4
5
6
7
8
Name
-IN
SCP
Vcc
CE
OUT
GND
OSC
FB
I/O
Description
I Error amplifier inverting input pin
I Soft start and SCP capacitor connection pin
Power supply
I Chip enable input pin（internal pull "H"）
O Totem-type output pin
Ground
O Capacitor and resistor connection pin for setting the oscillation frequency
O Error amplifier output pin
Absolute Maximum Ratings
CHARACTERISTICS
Supply voltage
SYMBOL
V
DD
VALUE
7
UNIT
V
Output current
Operating free-air temperature range
Storage temperature range
Power dissipation
I
O
T
ope
T
stg
-120/+120
-20 to 85
-65 to 150
500
mA
o
o
C
C
Pd
mW
Recommended Operating Conditions
Supply voltage, V
DD
Error amplifier input voltage
OSC capacitor
OSC resistor
Oscillator frequency
Output current
Operating free-air temperature
Symbol
V
DD
V
I
C
T
R
T
f
OSC
Min
2.6
0.5
100
1.0
Max
6.5
1.6
10000
10
Unit
V
V
pF
k
Ω
10
-20
1000
+30/-30
85
kHz
mA
o
I
O
T
ope
C
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AAT1109A
Electrical Characteristics,
V
DD
= 3.3V (Unless Otherwise Specified) (See Note 1)
Oscillator
Parameter
Test Condition
Min
Typ
Oscillation frequency
Frequency variation with
temperature
Frequency input stability
f
OSC
C
T
= 270pF, R
T
= 4.2k
Ω
400
500
5
Max Unit
600 KHz
f
dT
f
dV
V
DD
= 2.6V to 6.5V
%
%
1
Under-voltage Protection
Parameter
Test Condition
Min
Typ
Max
Unit
Upper threshold voltage
Lower threshold voltage
Hysteresis ( V
UPH
– V
UPL
)
V
UPH
V
UPL
V
HYS
T
A
= 25
o
C
T
A
= 25
o
C
T
A
= 25
o
C
T
A
=25
o
C.
2.12 2.47
1.96 2.28
0.3
2.85
2.63
V
V
V
Note1 : Typical values of all parameters are specified at
Short Circuit Protection Control
Parameter
Test Condition
Min
Typ
Max
Unit
Input threshold voltage
Short-circuit detect threshold
voltage
Charging current
V
r1
1.16 1.262
1.16 1.262
Vscp=0v
-1.0
-1.5
1.36
1.36
-2.15
V
V
µA
V
r 2
I
SCP
Soft start
Parameter
Test Condition
Min
Typ
Max
Unit
Charging current
Voltage at soft start
completion
Ics
V
ts
Vscp=0v
-1.0
-1.5
-2.15
1.36
µA
V
1.16 1.262
Shun Down Control
Parameter
Test Condition
Min
Typ
Max
Unit
Shut down release voltage
Shut down enable voltage
V
sdh
V
sdl
2.0
0.5
V
V
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AAT1109A
Electrical Characteristics,
V
DD
= 3.3V (Unless Otherwise Specified) (See Note 1)
Idle period adjustment section
Parameter
Test Conditions
Min
Typ
Max
Unit
Maximum duty cycle
t
DUTY
C
T
= 270pF, R
T
= 4.2k
Ω
V
FB
= 1.12v
75
85
93
%
EA (Error Amplifier)
Parameter
Test Condition
Input threshold voltage
V
T
input stability
V
T
variation with temperature
Input bias current
Output voltage swing
Output sink current
Output source current
Open-loop voltage
amplification
V
T
V
TdV
V
TdT
V
FB
=
0.7v
V
dd
= 2.6 to 6.5v
T
A
= -20
o
C to 90
o
C
Min
Typ Max Unit
1.249 1.262 1.275 V
2
8
mV
1
%
I
B
V
OM
+
V
OM
−
I
OM
+
I
OM
−
A
VD
FB=0.7V
FB=0.7V
3
-45
70
1.4
0.1
1.7
0.05
20
-75
85
1
0.2
µA
V
mA
µA
dB
Output section
Parameter
Test Condition
Typ
Max Unit
High-level output voltage
Low-level output voltage
Rise time
Fall time
V
OH
V
OL
T
rise
T
fall
I
O
=-30mA
I
O
=+30mA
C
L
=1000pF
C
L
=1000pF
1.9
2.3
0.8
100
100
1.2
V
V
nS
nS
Operating Current
Parameter
Test Condition
Min
Supply current
I
DD
−
OFF
I
DD
−
ON
Output ”OFF”state
R
T
=4.2k
Typ
1.3
Max Unit
mA
1.6
mA
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AAT1109A
How to set the time constant for soft start and short circuit protection
1.Soft start
At power on, the AAT1109A operates in soft start mode. The capacitor Cscp connected to SCP pin starts
charging at a constant current. In the soft start mode, the voltage at SCP pin (VSCP) is input to the PWM
comparator, so that the ON duty of the OUT pin is controlled by the VSCP. On completion of soft start
operation, the voltage at the SCP pin stays low, the input from soft start circuit to the PWM comparator
stay high, and enter the short circuit protection waiting state.
Soft start time
T
s
(sec)
~ 0.84 × C
SCP
(uF)
2.Short circuit protection
If the switching regulator output suddenly drops due to loading effect , the error amplifier output is fixed at
VOM
+
and capacitor C
SCP
starts charging. When the voltage at the SCP pin reaches approximately 1.26V
,the output pin set low and SCP pin stays low.
Once the protection circuit operates, the circuit can be recovered by setting the power supply.
Short circuit detection time
T
scp
(sec)
~ 0.84 × C
SCP
(uF)
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