Advanced Analog Technology, Inc.
Advanced Analog Technology, Inc
.
V 0.1
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
Pin Configuration
TOP VIEW
FB
OSC
GND
OUT
-IN
SCP
Vcc
CE
(SOP-8 PACKAGE)
(TSSOP-8 PACKAGE)
1
2
3
4
8
7
6
5
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.
Advanced Analog Technology, Inc.
Advanced Analog Technology, Inc
.
V 0.1
AAT1109A
Pin Description
Pin
# Name I/O
Description
1
-IN
I Error amplifier inverting input pin
2
SCP
I Soft start and SCP capacitor connection pin
3 Vcc
Power
supply
4 CE I
Chip enable input pininternal pull "H"
5
OUT
O Totem-type output pin
6 GND
Ground
7
OSC
O Capacitor and resistor connection pin for setting the oscillation frequency
8
FB
O Error amplifier output pin
Absolute Maximum Ratings
CHARACTERISTICS SYMBOL
VALUE
UNIT
Supply voltage
DD
V
7 V
Output current
O
I
-120/+120 mA
Operating free-air temperature range
ope
T
-20 to 85
o
C
Storage temperature range
stg
T
-65 to 150
o
C
Power dissipation
Pd
500
mW
Recommended Operating Conditions
Symbol
Min
Max
Unit
Supply voltage,
DD
V
DD
V
2.6 6.5 V
Error amplifier input voltage
V
I
0.5 1.6 V
OSC capacitor
T
C
100 10000 pF
OSC resistor
T
R
1.0 10 k
Oscillator frequency
OSC
f
10 1000 kHz
Output current
O
I
+30/-30 mA
Operating free-air temperature
ope
T
-20 85
o
C
Advanced Analog Technology, Inc.
Advanced Analog Technology, Inc
.
V 0.1
AAT1109A
Electrical Characteristics,
DD
V
= 3.3V (Unless Otherwise Specified) (See Note 1)
Oscillator
Parameter
Test Condition
Min
Typ Max Unit
Oscillation frequency
OSC
f
T
C = 270pF,
T
R = 4.2k
400
500 600 KHz
Frequency variation with
temperature
f
dT
5
%
Frequency input stability
dV
f
DD
V = 2.6V to 6.5V
1 %
Under-voltage Protection
Parameter
Test
Condition
Min
Typ
Max
Unit
Upper threshold voltage
UPH
V
A
T = 25
o
C
2.12 2.47 2.85 V
Lower threshold voltage
UPL
V
A
T = 25
o
C
1.96 2.28 2.63 V
Hysteresis (
UPH
V
UPL
V
)
HYS
V
A
T = 25
o
C
0.3 V
Note1 : Typical values of all parameters are specified at
A
T
=25
o
C.
Short Circuit Protection Control
Parameter
Test
Condition
Min
Typ
Max
Unit
Input threshold voltage
1
r
V
1.16 1.262
1.36
V
Short-circuit detect threshold
voltage
2
r
V
1.16 1.262
1.36
V
Charging current
SCP
I
Vscp=0v -1.0
-1.5
-2.15
A
Soft start
Parameter
Test
Condition
Min
Typ
Max
Unit
Charging current
Ics
Vscp=0v
-1.0
-1.5 -2.15 A
Voltage at soft start
completion
V
ts
1.16 1.262
1.36
V
Shun Down Control
Parameter
Test
Condition
Min
Typ
Max
Unit
Shut down release voltage
V
sdh
0.5
V
Shut down enable voltage
V
sdl
2.0
V
Advanced Analog Technology, Inc.
Advanced Analog Technology, Inc
.
V 0.1
AAT1109A
Electrical Characteristics,
DD
V
= 3.3V (Unless Otherwise Specified) (See Note 1)
Idle period adjustment section
Parameter
Test
Conditions
Min
Typ
Max
Unit
Maximum duty cycle
t
DUTY
T
C = 270pF,
T
R = 4.2k
V
FB
= 1.12v
75 85 93 %
EA (Error Amplifier)
Parameter
Test Condition
Min Typ Max
Unit
Input threshold voltage
V
T
V
FB
= 0.7v
1.249 1.262 1.275 V
V
T
input stability
V
TdV
V
dd
= 2.6 to 6.5v
2 8
mV
V
T
variation with temperature
V
TdT
A
T = -20
o
C to 90
o
C
1
%
Input bias current
I
B
0.1
1
A
+
OM
V
1.4
1.7
Output voltage swing
-
OM
V
0.05
0.2
V
Output sink current
+
OM
I
FB=0.7V 3
20
mA
Output source current
-
OM
I
FB=0.7V -45
-75
A
Open-loop voltage
amplification
VD
A
70
85
dB
Output section
Parameter
Test Condition
Typ Max Unit
High-level output voltage
V
OH
I
O
=-30mA 1.9
2.3
V
Low-level output voltage
V
OL
I
O
=+30mA
0.8
1.2
V
Rise time
T
rise
C
L
=1000pF
100
nS
Fall time
T
fall
C
L
=1000pF
100
nS
Operating Current
Parameter
Test Condition
Min Typ Max
Unit
OFF
DD
I
-
Output "OFF"state
1.3
mA
Supply current
ON
DD
I
-
R
T
=4.2k
1.6
mA
Advanced Analog Technology, Inc.
Advanced Analog Technology, Inc
.
V 0.1
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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