202058A.pdf

DATA SHEET
AAT1232
24V, 100mA Step-Up Converter
General Description
Features
The AAT1232 is a high frequency, high efficiency boost
converter capable of 24V maximum output voltage. The
internal power switch can deliver 100mA load current. It
is the ideal power solution to power OLED, LCD, and
CCD applications operating from a single cell lithium-ion
battery.
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The high switching frequency (up to 2MHz) provides fast
response to load transients with small external components. The fully integrated control IC simplifies the design
while reducing the total PCB footprint. The AAT1232
offers a true load disconnect feature which isolates the
load from the power source when EN/SET is pulled low.
This eliminates leakage current and maintains zero voltage at the output while disabled.
The output voltage can be dynamically set by activating
one of two reference levels (FB1 or FB2) through the SEL
logic pin. Optionally, Skyworks' Simple Serial Control™
(S2Cwire™) interface provides dynamic programmability
across a wide output voltage range through the EN/SET
pin.
The AAT1232 is available in a Pb-free, thermally-enhanced
16-pin 3x4mm TDFN low-profile package or a Pb-free
12-pin TSOPJW package.
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VIN Range: 2.7V to 5.5V
Maximum Output: 24V @ 100mA
True Load Disconnect
Dynamic Voltage Control Options
Hysteretic Control
▪ No External Compensation Components
▪ Excellent Load Transient Response
▪ High Efficiency at Light Load
Up to 2MHz Switching Frequency
Ultra-Small Inductor and Capacitors
Integrated Low RDS(ON) MOSFET Switches
Up to 85% Efficiency
<1μA Shutdown Current
Integrated Soft Start
Cycle-by-Cycle Current Limit
Short-Circuit, Over-Temperature Protection
Available in TSOPJW-12 or TDFN34-16 Package
-40°C to +85°C Temperature Range
Applications
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CCD Bias Circuit
Digital Still Cameras
LCD Bias Circuit
Mobile Handsets
MP3 Players
OLED Displays
PDAs and Notebook PCs
Typical Application
L1
2.2μH
Input:
2.7V~5.5V
C1
2.2μF
VP
VIN
D1
Schottky
24V @ 100mA
LIN
AAT1232
R1
576kΩ
C2
2.2μF, 25V
SW
FB1
PGND
R2
10.0kΩ
EN/SET
FB2
SEL
GND
R3
20.0kΩ
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
1
DATA SHEET
AAT1232
24V, 100mA Step-Up Converter
Pin Descriptions
Pin #
TSOPJW-12
TDFN34-16
Symbol
1
15, 16
VP
2
14
EN/SET
3
13
SEL
4
5
12
11
VIN
N/C
6, 7
9, 10
SW
8
6, 7, 8
PGND
9
5
GND
10
4
FB2
11
3
FB1
12
1, 2
LIN
N/A
EP
Function
Input power pin; connected to the source of the P-channel MOSFET. Connect a 2.2μF or
larger capacitor from these pins to PGND.
IC active high enable pin. Alternative input pin for S2Cwire control utilizing FB2 reference.
Logic high selects FB1 high output reference; logic low selects FB2 low output reference.
Pull low for S2Cwire control. See Tables 1 and 2.
Input voltage for the converter. Connect this pin directly to the VP pin.
No connection. Do not make any connection to this pin.
Boost converter switching node. Connect the power inductor between the SW pin and
the LIN pin.
Power ground for the boost converter; connected to the source of the internal N-channel
MOSFET. Connect input and output capacitor returns to PGND.
Ground pin.
Feedback pin for low output voltage set point. Pin set to 0.6V when SEL is low and disabled when SEL is high. Voltage is set from 0.6V to 1.2V using S2Cwire control.
Feedback pin for high output voltage set point. Pin set to 1.2V when SEL is high and
disabled when SEL is low. Disabled with S2Cwire control.
Switched power input. Connected to the power inductor.
Exposed paddle (bottom). Internally connected to SW. May be externally connected to
SW pins or left floating. Do not connect to GND or PGND.
Pin Configuration
TSOPJW-12
(Top View)
VP
EN/SET
SEL
VIN
N/C
SW
2
1
12
2
11
3
10
4
9
5
8
6
7
TDFN34-16
(Top View)
LIN
FB1
FB2
GND
PGND
SW
LIN
LIN
FB1
FB2
GND
PGND
PGND
PGND
1
16
2
15
3
14
4
13
5
12
6
11
7
10
8
9
VP
VP
EN/SET
SEL
VIN
N/C
SW
SW
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
DATA SHEET
AAT1232
24V, 100mA Step-Up Converter
Absolute Maximum Ratings1
TA = 25°C, unless otherwise noted.
Symbol
Description
Value
Units
VIN, VP
SW
LIN, EN/SET, SEL,
FB1, FB2
TJ
TS
TLEAD
Input Voltage
Switching Node
-0.3 to 6.0
28
V
V
VIN + 0.3
V
-40 to 150
-65 to 150
300
°C
°C
°C
Value
Units
Maximum Rating
Operating Temperature Range
Storage Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
Recommended Operating Conditions
Symbol
Description
JA
Thermal Resistance
PD
Maximum Power Dissipation (TA = 25°C)
TDFN34-16
TSOPJW-12
TDFN34-16
TSOPJW-12
44
160
2270
625
°C/W
mW
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.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
3
DATA SHEET
AAT1232
24V, 100mA Step-Up Converter
Electrical Characteristics1
TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C, VIN = 3.6V.
Symbol
Description
Conditions
Min
Power Supply
VIN
Input Voltage Range
VOUT(MAX)
Maximum Output Voltage
2.7
VLOADREG
VLINEREG/
VIN
RDS(ON)L
RDS(ON)IN
Load Regulation
VIN Rising
Hysteresis
VIN Falling
SEL = GND, VOUT = 18V, IOUT = 0,
R3 = 20k2, Switching
SEL = GND, FB2 = 1.5V, Not Switching
EN/SET = GND
2.7V < VIN < 5.5V, VOUT = 24V
IOUT = 0 to 100mA, VIN = 2.7V to 5.0V,
SEL = High
IOUT = 0 to 100mA, VIN = 2.7V to 5.0V,
SEL = Low
IOUT = 0 to 100mA, R3 = 20k3
Line Regulation
VIN = 2.7V to 5.5V, R3 = 20k
TSS
Soft-Start Time
VUVLO
IQ
UVLO Threshold
Quiescent Current
ISHDN
IOUT
VIN Pin Shutdown Current
Output Current
FB1
FB1 Reference Voltage
FB2
FB2 Reference Voltage
2.7V
5.5V
2.7V
5.5V
5.5
24
2.7
V
V
V
mV
V
0.3
40
mA
70
1.0
100
μA
mA
μA
1.164
1.2
1.236
V
0.582
0.6
0.618
V
3
VIN = 3.6V
=
=
=
=
Units
150
From Enable to Output Regulation;
VOUT = 15V
VIN
VIN
VIN
VIN
Max
1.8
Low Side Switch On Resistance
Input Disconnect Switch On Resistance
TSD
Over-Temperature Shutdown Threshold
THYS
Shutdown Hysteresis
ILIM
N-Channel Current Limit
SEL, EN/SET
SEL Threshold Low
VSEL(L)
VSEL(H)
SEL Threshold High
VEN/SET(L)
Enable Threshold Low
VEN/SET(H)
Enable Threshold High
TEN/SET LO
EN/SET Low Time
TEN/SET HI MIN Minimum EN/SET High Time
TEN/SET HI MAX Maximum EN/SET High Time
TOFF
EN/SET Off Timeout
TLAT
EN/SET Latch Timeout
IEN/SET
EN/SET Input Leakage
Typ
0.02
%/mA
0.6
%/V
0.08
0.18

0.35
ms
140
15
3.0
°C
°C
A

0.4
1.4
0.4
1.4
0.3
75
50
-1
75
500
500
1
V
V
V
V
μs
ns
μs
μs
μs
μA
1. The AAT1232 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. Switching input current will vary with R1, R2, R3 resistor values.
3. Some improvement in line and load regulation is possible with smaller resistor values.
4
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
DATA SHEET
AAT1232
24V, 100mA Step-Up Converter
Typical Characteristics
Efficiency vs. Output Current
Output Error vs. Output Current
(VOUT = 18V; R3 = 20kΩ
Ω)
90
70
VIN = 3.6V
VIN = 4.2V
60
Output Error (%)
VIN = 5V
80
Efficiency (%)
(VOUT = 18V; R3 = 20kΩ
Ω)
1.5
50
40
30
VIN = 5V
1.0
0.5
VIN = 4.2V
0.0
VIN = 3.6V
-0.5
VIN = 2.7V
-1.0
-1.5
20
0.1
1
10
0.1
100
Output Current (mA)
1.5
Output Error (%)
Efficiency (%)
(VOUT = 20V; R3 = 20kΩ
Ω)
VIN = 5V
70
VIN = 3.6V
VIN = 4.2V
60
50
40
30
1
10
VIN = 5V
1.0
0.5
VIN = 4.2V
0.0
VIN = 3.6V
-0.5
VIN = 2.7V
-1.0
-1.5
20
0.1
100
0.1
Output Current (mA)
Output Error (%)
Efficiency (%)
1.5
70
VIN = 3.6V
VIN = 4.2V
100
(VOUT = 24V; R3 = 20kΩ
Ω)
VIN = 5V
60
10
Output Error vs. Output Current
(VOUT = 24V; R3 = 20kΩ)
80
1
Output Current (mA)
Efficiency vs. Output Current
90
100
Output Error vs. Output Current
(VOUT = 20V; R3 = 20kΩ
Ω)
80
10
Output Current (mA)
Efficiency vs. Output Current
90
1
50
40
30
VIN = 5V
VIN = 4.2V
1.0
0.5
0.0
VIN = 3.6V
-0.5
VIN = 2.7V
-1.0
-1.5
20
0.1
1
10
Output Current (mA)
100
0.1
1
10
100
Output Current (mA)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
5
DATA SHEET
AAT1232
24V, 100mA Step-Up Converter
Typical Characteristics
Line Regulation
Output Voltage Error vs. Temperature
(VOUT = 18V; R3 = 20kΩ
Ω)
(VIN = 5V; VOUT = 18V; IOUT = 100mA)
0.2
2.5
2.0
0.1
Output Error (%)
Accuracy (%)
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
0.0
-0.1
-0.2
-0.3
-0.4
-2.0
-2.5
2.5
3
3.5
4
4.5
5
5.5
-0.5
-40
6
-15
No Load Quiescent Current vs. Input Voltage
1.1
Supply Current (mA)
Supply Current (mA)
0.4
0.36
0.32
0.28
0.24
0.2
0.16
0.12
0.08
4
4.5
5
5.5
0.9
0.8
0.6
0.5
0.3
0.2
0.0
-40
10
35
Output Ripple
Output Ripple
(VIN = 4.2V; VOUT = 18V; IOUT = 100mA)
(VIN = 4.2V; VOUT = 18V; No Load)
60
85
18.2
1.0
18.0
4.0
18.0
0.8
17.8
3.0
17.8
0.6
17.6
2.0
17.6
0.4
17.4
1.0
17.4
0.2
17.2
0.0
17.2
0.0
-1.0
17.0
Time (500ns/div)
Output Voltage
(top) (V)
5.0
-0.2
17.0
Time (100µs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
Inductor Current
(bottom) (A)
18.2
Inductor Current
(bottom) (A)
Output Voltage
(top) (V)
-15
Temperature (°°C)
Input Voltage (V)
6
85
(VIN = 3.6V; VOUT = 18V)
1.2
3.5
60
No Load Input Current vs. Temperature
(VOUT = 18V; EN_High)
3
35
Temperature (°°C)
Input Voltage (V)
2.5
10
DATA SHEET
AAT1232
24V, 100mA Step-Up Converter
Load Transient Response
Load Transient Response
(VIN = 4.2V; IOUT = 20mA–60mA; VOUT = 18V)
(VIN = 3.6V; IOUT = 20mA–60mA; VOUT = 12V)
18.05
1.2
18.00
0.9
17.95
0.6
17.90
0.3
17.85
0.0
17.80
-0.3
Output Voltage (V) (top)
1.5
12.10
1.50
12.05
1.20
12.00
0.90
11.95
0.60
11.90
0.30
11.85
0.00
-0.30
11.80
Time (200µs/div)
Time (200µs/div)
P-Channel RDS(ON) vs. Input Voltage
N-Channel RDS(ON) vs. Input Voltage
160
300
280
140
120°C
260
100°C
240
RDS(ON) (mΩ)
RDS(ON) (mΩ
Ω)
Inductor Current (A) (bottom)
18.10
Inductor Current (A) (bottom)
Output Voltage (V) (top)
Typical Characteristics
220
200
180
25°C
160
140
2.5
3
120°C
120
80
25°C
60
85°C
3.5
4
4.5
5
5.5
6
Input Voltage (V)
100°C
100
85°C
40
2.5
3
3.5
4
4.5
5
5.5
6
Input Voltage (V)
Soft Start
16
2.8
12
2.4
8
2.0
4
1.6
0
1.2
-4
0.8
-8
0.4
-12
0.0
-16
-0.4
Input Current
(bottom) (A)
Enable Voltage (middle) (V)
Output Voltage (top) (V)
(VIN = 3.6V; CIN = 2.2µF; IOUT = 100mA; VOUT = 12V)
Time (200µs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
7
DATA SHEET
AAT1232
24V, 100mA Step-Up Converter
Functional Block Diagram
VIN
LIN
VP
Output
Timer
EN/SET
SW
Control
FB1
1.2V
VREF
Output
Select
FB2
SEL
GND
Functional Description
The AAT1232 consists of a DC/DC boost controller, an
integrated slew rate controlled input disconnect MOSFET
switch, and a MOSFET power switch. A high voltage rectifier, power inductor, output capacitor, and resistor
divider network are required to implement a DC/DC
boost converter.
Control Loop
The AAT1232 provides the benefits of current mode control with a simple hysteretic feedback loop. The device
maintains exceptional DC regulation, transient response,
and cycle-by-cycle current limit without additional compensation components.
8
PGND
The AAT1232 modulates the power MOSFET switching
current in response to changes in output voltage. This
allows the voltage loop to directly program the required
inductor current in response to changes in the output
load.
The switching cycle initiates when the N-channel MOSFET
is turned ON and current ramps up in the inductor. The
ON interval is terminated when the inductor current
reaches the programmed peak current level. During the
OFF interval, the input current decays until the lower
threshold, or zero inductor current, is reached. The lower
current is equal to the peak current minus a preset hysteresis threshold which determines the inductor ripple
current. The peak current is adjusted by the controller
until the output current requirement is met.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
DATA SHEET
AAT1232
24V, 100mA Step-Up Converter
The magnitude of the feedback error signal determines
the average input current. Therefore, the AAT1232 controller implements a programmed current source connected to the output capacitor and load resistor. There is
no right-half plane zero, and loop stability is easily
achieved with no additional compensation components.
Increased load current results in a drop in the output
feedback voltage (FB1 or FB2) sensed through the feedback resistors (R1, R2, R3). The controller responds by
increasing the peak inductor current, resulting in higher
average current in the inductor. Alternatively, decreased
output load results in an increase in the output feedback
voltage (FB1 or FB2 pin). The controller responds by
decreasing the peak inductor current, resulting in lower
average current in the inductor.
At light load, the inductor OFF interval current goes
below zero and the boost converter enters discontinuous
mode operation. Further reduction in the load results in
a corresponding reduction in the switching frequency.
AAT1232 pulsed frequency operation reduces switching
losses and maintains high efficiency at light loads.
Operating frequency varies with changes in the input
voltage, output voltage, and inductor size. Once the
boost converter has reached continuous mode, further
increases in the output load will not significantly increase
the operating frequency. A small 2.2μH (±20%) inductor
is selected to maintain high frequency switching (up to
2MHz) and high efficiency operation for outputs from
10V to 24V.
Output Voltage Programming
The output voltage may be programmed through a resistor divider network located from output capacitor to FB1/
FB2 pins to ground. Pulling the SEL pin high activates the
FB1 pin which maintains a 1.2V reference voltage, while
the FB2 reference is disabled. Pulling the SEL pin low
activates the FB2 pin which maintains a 0.6V reference,
while the FB1 reference is disabled. This function allows
dynamic selection between two distinct output voltages
across a 2X range (maximum). An additional resistor
between FB1 and FB2 allows the designer to program the
outputs across a reduced <2X range.
Alternatively, the output voltage may be programmed to
any of 16 voltage levels using the S2Cwire serial digital
input. The single wire S2Cwire interface provides highspeed output voltage programmability across a 2X output voltage range. S2Cwire functionality is enabled by
pulling the SEL pin low and providing S2Cwire input to
the EN/SET pin. Table 2 details the FB2 reference voltage
versus S2Cwire rising edges.
Soft Start / Enable
The input disconnect switch is activated when a valid
input voltage is present and the EN/SET pin is pulled
high. The slew rate control on the P-channel MOSFET
ensures minimal inrush current as the output voltage is
charged to the input voltage, prior to switching of the
N-channel power MOSFET. Monotonic turn-on is guaranteed by the built-in soft-start circuitry. Soft-start eliminates output voltage overshoot across the full input
voltage range and all loading conditions.
Some applications may require the output to be active
when a valid input voltage is present. In these cases,
add a 10k resistor between the VIN, VP, and EN/SET
pins to avoid startup issues.
Current Limit and Over-Temperature
Protection
The switching of the N-channel MOSFET terminates when
current limit of 3.0A (typical) is exceeded. This minimizes
power dissipation and component stresses under overload and short-circuit conditions. Switching resumes
when the current decays below the current limit.
Thermal protection disables the AAT1232 when internal
dissipation becomes excessive. Thermal protection disables both MOSFETs. The junction over-temperature
threshold is 140°C with 15°C of temperature hysteresis.
Once an over-temperature or over-current fault condition
is removed, the output voltage automatically recovers.
Under-Voltage Lockout
Internal bias of all circuits is controlled via the VIN input.
Under-voltage lockout (UVLO) guarantees sufficient VIN
bias and proper operation of all internal circuitry prior to
activation.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202058A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
9
DATA SHEET
AAT1232
24V, 100mA Step-Up Converter
R4
10k
JP1
VIN
3
2
1
Enable
JP2
3
2
1
C1
2.2μF
1
2
3
4
5
6
VP
LIN
EN/SET
FB1
SEL
FB2
VIN
GND
N/C
PGND
SW
SW
D1
Schottky
L1
2.2μH
U1
12
11
10
9
8
7
VOUT
R1
576k
C2
2.2μF
R2
10k
R3
20k
Select
U1 AAT1232 TSOPJW12
C1 10V 0805 2.2μF
C2 25V 0805 2.2μF
D1 30V 0.5A MBR0530T SOD-123
L1 2.2μH NR4018T2R2
R1 576k 0603
R2, R4 10k 0603
R3 20k 0603
R4 10k 0603
Figure 1: AAT1232 Demo Board Schematic.
Application Information
capacitors sized as small as 0603 are available which
meet these requirements.
Selecting DC/DC Boost Capacitors
Large capacitance tantalum or solid-electrolytic capacitors
may be necessary to meet stringent output ripple and
transient load requirements. These can replace (or be
used in parallel with) ceramic capacitors. Both tantalum
and OSCON-type capacitors are suitable due to their low
ESR and excellent temperature stability (although they
exhibit much higher ESR than MLC capacitors). Aluminumelectrolytic types are less suitable due to their high ESR
characteristics and temperature drift. Unlike MLC capacitors, these types are polarized and proper orientation on
input and output pins is required. 30% to 70% voltage
derating is recommended for tantalum capacitors.
The high output ripple inherent in the boost converter
necessitates low impedance output filtering. Multi-layer
ceramic (MLC) capacitors provide small size and adequate capacitance, low parasitic equivalent series resistance (ESR) and equivalent series inductance (ESL), and
are well suited for use with the AAT1232 boost regulator.
MLC capacitors of type X7R or X5R are recommended to
ensure good capacitance stability over the full operating
temperature range.
The output capacitor is sized to maintain the output load
without significant voltage droop during the power switch
ON interval, when the output diode is not conducting. A
ceramic output capacitor from 2.2μF to 4.7μF is recommended. Typically, 25V rated ceramic capacitors are
required for the 24V boost output. Ceramic capacitors
sized as small as 0805 are available which meet these
requirements.
MLC capacitors exhibit significant capacitance reduction
with applied voltage. Output ripple measurements should
confirm that output voltage droop is acceptable.
The boost converter input current flows during both ON
and OFF switching intervals. The input ripple current is
less than the output ripple and, as a result, less input
capacitance is required. A ceramic output capacitor from
1μF to 3.3μF is recommended. Minimum 6.3V rated
ceramic capacitors are required at the input. Ceramic
10
Selecting the Output Diode
To ensure minimum forward voltage drop and no recovery, high voltage Schottky diodes are considered the
best choice for the AAT1232 boost converter. The
AAT1232 output diode is sized to maintain acceptable
efficiency and reasonable operating junction temperature under full load operating conditions. Forward voltage (VF) and package thermal resistance (JA) are the
dominant factors to consider in selecting a diode. The
diode’s published current rating may not reflect actual
operating conditions and should be used only as a comparative measure between similarly rated devices. 20V
rated Schottky diodes are recommended for outputs less
than 15V, while 30V rated Schottky diodes are recommended for outputs greater than 15V.
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DATA SHEET
AAT1232
24V, 100mA Step-Up Converter
The average diode current is equal to the output current.
IAVG = IOUT
The average output current multiplied by the forward
diode voltage determines the loss of the output diode.
PLOSS_DIODE = IAVG · VF
= IOUT · VF
Diode junction temperature can be estimated.
TJ = TAMB + ΘJA · PLOSS_DIODE
The junction temperature should be maintained below
110ºC, but may vary depending on application and/or
system guidelines. The diode JA can be minimized with
additional PCB area on the cathode. PCB heatsinking the
anode may degrade EMI performance.
The reverse leakage current of the rectifier must be considered to maintain low quiescent (input) current and
high efficiency under light load. The rectifier reverse current increases dramatically at high temperatures.
The maximum duty cycle can be estimated from the
relationship for a continuous mode boost converter.
Maximum duty cycle (DMAX) is the duty cycle at minimum
input voltage (VIN(MIN)):
DMAX =
Where VF is the Schottky diode forward voltage and can
be estimated at 0.5V. Manufacturer’s specifications list
both the inductor DC current rating, which is a thermal
limitation, and peak inductor current rating, which is
determined
by
the
saturation
characteristics.
Measurements at full load and high ambient temperature
should be completed to ensure that the inductor does
not saturate or exhibit excessive temperature rise.
The output inductor (L) is selected to avoid saturation at
minimum input voltage, maximum output load conditions. Peak current may be calculated from the following
equation, again assuming continuous conduction mode.
Worst-case peak current occurs at minimum input voltage (maximum duty cycle) and maximum load. Switching
frequency can be estimated at 500kHz with a 2.2μH
inductor.
Selecting the Boost Inductor
The AAT1232 controller utilizes hysteretic control and
the switching frequency varies with output load and
input voltage. The value of the inductor determines the
maximum switching frequency of the AAT1232 boost
converter. Increased output inductance decreases the
switching frequency, resulting in higher peak currents
and increased output voltage ripple. To maintain 2MHz
maximum switching frequency, an output inductor sized
from 1.5μH to 2.7μH is recommended.
The switching period is divided between ON and OFF
time intervals.
1
= TON + TOFF
FS
The ON time is the period which the N-channel power
MOSFET is conducting and storing energy in the boost
inductor. Duty cycle is defined as the ON time divided by
the total switching interval.
D=
TON
TON + TOFF
(VOUT + VF - VIN(MIN))
(VOUT + VF)
IPEAK =
IOUT
D
· VIN(MIN)
+ MAX
(1 - DMAX)
(2 · FS · L)
The RMS current flowing through the boost inductor is
equal to the DC plus AC ripple components. Under worstcase RMS conditions, the current waveform is critically
continuous. The resulting RMS calculation yields worstcase inductor loss. The RMS value should be compared
against the manufacturer’s temperature rise, or thermal
derating, guidelines.
IRMS =
IPEAK
3
For a given inductor type, smaller inductor size leads to
an increase in DCR winding resistance and, in most
cases, increased thermal impedance. Winding resistance
degrades boost converter efficiency and increases the
inductor operating temperature.
PLOSS_INDUCTOR = IRMS2 · DCR
= TON ⋅ FS
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11
DATA SHEET
AAT1232
24V, 100mA Step-Up Converter
To ensure high reliability, the inductor temperature
should not exceed 100°C. Manufacturer’s recommendations should be consulted. In some cases, PCB heatsinking applied to the AAT1232 LIN node (non-switching) can
improve the inductor’s thermal capability. PCB heatsinking may degrade EMI performance when applied to the
SW node (switching) of the AAT1232.
Shielded inductors provide decreased EMI and may be
required in noise sensitive applications. Unshielded chip
inductors provide significant space savings at a reduced
cost compared to shielded (wound and gapped) inductors. Chip-type inductors have increased winding resistance when compared to shielded, wound varieties.
Setting the Output Voltage
The output voltage may be programmed through a resistor divider network located from the output to FB1 and
FB2 pins to ground. Pulling the SEL pin high activates the
FB1 pin which maintains a 1.2V reference voltage, while
the FB2 reference is disabled. Pulling the SEL pin low
activates the FB2 pin which maintains a 0.6V reference,
while the FB1 reference is disabled.
The AAT1232 output voltage can be programmed by one
of three methods. First, the output voltage can be static
by pulling the SEL logic pin either high or low. Second,
the output voltage can be dynamically adjusted between
two pre-set levels within a 2X operating range by toggling the SEL logic pin. Third, the output can be dynamically adjusted to any of 16 preset levels within a 2X
operating range using the integrated S2Cwire single wire
interface via the EN/SET pin.
Option 1: Static Output Voltage
A static output voltage can be configured by pulling the
SEL either high or low. SEL pin high activates the FB1
reference pin to 1.2V (nominal). Alternatively, the SEL
pin is pulled low to activate the FB2 reference at 0.6V
(nominal). Table 1 provides details of resistor values for
common output voltages from 10V to 24V for SEL = High
and SEL = Low options.
In the static configuration, the FB1 pin should be directly connected to FB2. The resistor between FB1 and FB2
pins is not required.
Option 2: Dynamic Voltage
Control Using SEL Pin
The output may be dynamically adjusted between two
output voltages by toggling the SEL logic pin. Output
voltages VOUT(1) and VOUT(2) correspond to the two output
12
references, FB1 and FB2. Pulling the SEL logic pin high
activates VOUT(1), while pulling the SEL logic pin low activates VOUT(2).
The minimum output voltage must be greater than the
specified maximum input voltage plus margin to maintain proper operation of the AAT1232 boost converter. In
addition, the ratio of output voltages VOUT(2)/VOUT(1) is
always less than 2.0, corresponding to a 2X (maximum)
programmable range.
Table 1 is provided to allow programming of common
output voltages using Option 1 or 2. The feedback references FB1 and FB2 are enabled or disabled using the SEL
logic pin, corresponding to VOUT(1) and VOUT(2).
Option 3: Dynamic Voltage
Control Using S2Cwire Interface
The output can be dynamically adjusted by the host controller to any of 16 pre-set output voltage levels using
the integrated S2Cwire interface. The EN/SET pin serves
as the S2Cwire interface input. The SEL pin must be
pulled low when using the S2Cwire interface.
S2Cwire Serial Interface
Skyworks' S2Cwire serial interface is a proprietary highspeed single-wire interface available only from Skyworks.
The S2Cwire interface records rising edges of the EN/SET
input and decodes into 16 different states. Each state
corresponds to a voltage setting on the FB2 pin.
S2Cwire Serial Interface Timing
The S2Cwire serial interface has flexible timing. Data can
be clocked-in at speeds up to 1MHz. After data has been
submitted, EN/SET is held high to latch the data for a
period TLAT. The output is subsequently changed to the
predetermined voltage. When EN/SET is set low for a time
greater than TOFF, the AAT1232 is disabled. When disabled, the register is reset to the default value, which sets
the FB2 pin to 0.6V if EN is subsequently pulled high.
S2Cwire Output Voltage Programming
The AAT1232 is programmed through the S2Cwire interface according to Table 2. The rising clock edges received
through the EN/SET pin determine the feedback reference and output voltage set-point. Upon power up with
the SEL pin low and prior to S2Cwire programming, the
default feedback reference voltage is set to 0.6V.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT1232
24V, 100mA Step-Up Converter
R3 = 4.99kΩ
R3 = 20.0kΩ
VOUT
(SEL = High)
VOUT
(SEL = Low)
R1 (kΩ)
R2 (kΩ)
R1 (kΩ)
R2 (kΩ)
10.0
12.0
15.0
16.0
18.0
20.0
24.0
12.0
15.0
16.0
18.0
15.0
16.0
18.0
18.0
20.0
24.0
24.0
10.0
12.0
15.0
16.0
18.0
20.0
24.0
10.0
10.0
10.0
10.0
12.0
12.0
12.0
15.0
15.0
15.0
18.0
36.5
44.2
57.6
61.9
69.8
78.7
95.3
78.7
95.3
121
127
143
162
196
75.0
76.8
76.8
78.7
90.9
93.1
93.1
115
118
118
143
0
0
0
0
0
0
0
0
0
0
0
0
0
0
3.32
1.65
1.24
0.562
3.01
2.49
1.65
3.32
2.49
1.24
2.49
147
182
232
249
280
316
383
316
383
487
511
590
649
787
301
309
309
316
374
374
374
464
475
475
576
0
0
0
0
0
0
0
0
0
0
0
0
0
0
13.0
6.65
4.99
2.21
12.1
10.0
6.65
13.3
10.0
4.99
10.0
Table 1: SEL Pin Voltage Control Resistor Values (1% resistor tolerance).
EN/SET Rising Edges
FB2 Reference Voltage (V)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
0.60 (Default)
0.64
0.68
0.72
0.76
0.80
0.84
0.88
0.92
0.96
1.00
1.04
1.08
1.12
1.16
1.20
Table 2: S2Cwire Voltage Control Settings (SEL = Low).
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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13
DATA SHEET
AAT1232
24V, 100mA Step-Up Converter
THI
TLO
TOFF
T LAT
EN/SET
1
2
Data Reg
n-1
n ≤ 16
0
n
0
Figure 3: S2Cwire Timing Diagram to Program the Output Voltage.
PCB Layout Guidelines
Boost converter performance can be adversely affected
by poor layout. Possible impact includes high input and
output voltage ripple, poor EMI performance, and reduced
operating efficiency. Every attempt should be made to
optimize the layout in order to minimize parasitic PCB
effects (stray resistance, capacitance, inductance) and
EMI coupling from the high frequency SW node.
3.
4.
5.
A suggested PCB layout for the AAT1232 boost converter
is shown in Figures 4 and 5. The following PCB layout
guidelines should be considered:
6.
1.
7.
2.
Minimize the distance from capacitor C1 and C2
negative terminal to the PGND pins. This is especially true with output capacitor C2, which conducts
high ripple current from the output diode back to the
PGND pins.
Place the feedback resistors close to the output terminals. Route the output pin directly to resistor R1
Figure 4: AAT1232 Evaluation Board
Top Side Layout.
14
to maintain good output regulation. R3 should be
routed close to the output GND pin.
Minimize the distance between L1 to D1 and switching pin SW; minimize the size of the PCB area connected to the SW pin.
Maintain a ground plane and connect to the IC RTN
pin(s) as well as the GND terminals of C1 and C2.
Consider additional PCB area on D1 cathode to maximize heatsinking capability. This may be necessary
when using a diode with a high thermal resistance.
When using the TDFN34-16 package, connect paddle
to SW pin or leave floating. Do not connect to RTN/
GND conductors.
To avoid problems at startup, add a 10k resistor
between the VIN, VP and EN/SET pins (R4). This is
critical in applications requiring immunity from input
noise during “hot plug” events, e.g. when plugged
into an active USB port.
Figure 5: AAT1232 Evaluation Board
Bottom Side Layout.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT1232
24V, 100mA Step-Up Converter
Manufacturer
Part Number
Rated IF(AV)
Current (A)1
Rated
Voltage (V)
Thermal Resistance
(ΘJA, °C/W)1
Case
Diodes, Inc.
Diodes, Inc.
Diodes, Inc.
Diodes, Inc.
ON Semi
ON Semi
Zetex
Zetex
B340LA
SD103AWS
BAT42WS
B0520WS
MBR130LSFT
MBR0530T
ZHCS350
BAT54
3.00
0.35
0.20
0.50
1.00
0.50
0.35
0.20
40
30
30
20
30
30
40
30
25
625
625
426
325
206
330
330
SMA
SOD-323
SOD-323
SOD-323
SOD-123
SOD-123
SOD-523
SOT-23
Table 3: Typical Surface Mount Schottky Rectifiers for Various Output Loads
(select TJ < 110°C in application circuit).
Manufacturer
Part Number
Inductance
(μH)
Max DC ISAT
Current (A)
DCR
(Ω)
Size (mm)
LxWxH
Type
Sumida
Sumida
Sumida
Murata
Murata
Taiyo Yuden
Taiyo Yuden
Coiltronics
Coiltronics
Coiltronics
CDRH4D22/HP-2R2
CDR4D11/HP-2R4
CDRH4D18-2R2
LQH662N2R2M03
LQH55DN2R2M03
NR4018T2R2
NR3015T2R2
SD3814-2R2
SD3114-2R2
SD3112-2R2
2.2
2.4
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.50
1.70
1.32
3.30
3.20
2.70
1.48
1.90
1.48
1.12
35
105
75
19
29
60
60
77
86
140
5.0x5.0x2.4
4.8x4.8x1.2
5.0x5.0x2.0
6.3x6.3x4.7
5.0x5.7x4.7
4.0x4.0x1.8
3.0x3.0x1.5
3.8x3.8x1.4
3.1x3.1x1.4
3.1x3.1x1.2
Shielded
Shielded
Shielded
Shielded
Non-Shielded
Shielded
Shielded
Shielded
Shielded
Shielded
Table 4: Typical Surface Mount Inductors for Various Output Loads
(select IPEAK < ISAT).
Manufacturer
Part Number
Type
Value (μF)
Voltage (V)
Temp. Co.
Footprint
LxWxH (mm)
Murata
Murata
Murata
Murata
Murata
GRM188R60J475KE19D
GRM188R61A225KE34D
GRM188R61C225KA88
GRM21BR61E225KA12L
GRM188R61E105KA12D
Ceramic
Ceramic
Ceramic
Ceramic
Ceramic
2.2
2.2
2.2
2.2
1.0
6.3
10
16
25
25
X5R
X5R
X5R
X5R
X5R
0603
0603
0805
0805
0603
Table 5: Typical Surface Mount Capacitors for Various Output Loads.
1. Results may vary depending on test method used and specific manufacturer.
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15
DATA SHEET
AAT1232
24V, 100mA Step-Up Converter
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
TSOPJW-12
TDFN34-16
SXXYY
SXXYY
AAT1232ITP-T1
AAT1232IRN-T1
Skyworks Green™ products are compliant with
all applicable legislation and are halogen-free.
For additional information, refer to Skyworks
Definition of Green™, document number
SQ04-0074.
Package Information3
TSOPJW-12
2.85 ± 0.20
2.40 ± 0.10
0.20 + 0.10
- 0.05
0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC
7° NOM
0.04 REF
0.055 ± 0.045
0.15 ± 0.05
+ 0.10
1.00 - 0.065
0.9625 ± 0.0375
3.00 ± 0.10
4° ± 4°
0.45 ± 0.15
0.010
2.75 ± 0.25
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
3. The leadless package family, which includes QFN, TQFN, DFN, TDFN and STDFN, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing
process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection.
16
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DATA SHEET
AAT1232
24V, 100mA Step-Up Converter
TDFN34-16
3.000 ± 0.050
1.600 ± 0.050
Detail "A"
3.300 ± 0.050
4.000 ± 0.050
Index Area
0.350 ± 0.100
Top View
0.230 ± 0.050
Bottom View
C0.3
(4x)
0.050 ± 0.050
0.450 ± 0.050
0.850 MAX
Pin 1 Indicator
(optional)
0.229 ± 0.051
Side View
Detail "A"
All dimensions in millimeters.
Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.
Information in this document is provided in connection with Skyworks Solutions, Inc. (“Skyworks”) products or services. These materials, including the information contained herein, are provided by Skyworks as a
service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility for errors or omissions in these materials or the information contained herein. Skyworks may change its documentation, products, services, specifications or product descriptions at any time, without notice. Skyworks makes no commitment to update the materials or information and shall have no
responsibility whatsoever for conflicts, incompatibilities, or other difficulties arising from any future changes.
No license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document. Skyworks assumes no liability for any materials, products or information provided hereunder, including the sale, distribution, reproduction or use of Skyworks products, information or materials, except as may be provided in Skyworks Terms and Conditions of Sale.
THE MATERIALS, PRODUCTS AND INFORMATION ARE PROVIDED “AS IS” WITHOUT WARRANTY OF ANY KIND, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHERWISE, INCLUDING FITNESS FOR A PARTICULAR
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NOT WARRANT THE ACCURACY OR COMPLETENESS OF THE INFORMATION, TEXT, GRAPHICS OR OTHER ITEMS CONTAINED WITHIN THESE MATERIALS. SKYWORKS SHALL NOT BE LIABLE FOR ANY DAMAGES, INCLUDING BUT NOT LIMITED TO ANY SPECIAL, INDIRECT, INCIDENTAL, STATUTORY, OR CONSEQUENTIAL DAMAGES, INCLUDING WITHOUT LIMITATION, LOST REVENUES OR LOST PROFITS THAT MAY RESULT FROM
THE USE OF THE MATERIALS OR INFORMATION, WHETHER OR NOT THE RECIPIENT OF MATERIALS HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Skyworks products are not intended for use in medical, lifesaving or life-sustaining applications, or other equipment in which the failure of the Skyworks products could lead to personal injury, death, physical or environmental damage. Skyworks customers using or selling Skyworks products for use in such applications do so at their own risk and agree to fully indemnify Skyworks for any damages resulting from such improper
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Customers are responsible for their products and applications using Skyworks products, which may deviate from published specifications as a result of design defects, errors, or operation of products outside of published parameters or design specifications. Customers should include design and operating safeguards to minimize these and other risks. Skyworks assumes no liability for applications assistance, customer product
design, or damage to any equipment resulting from the use of Skyworks products outside of stated published specifications or parameters.
Skyworks, the Skyworks symbol, and “Breakthrough Simplicity” are trademarks or registered trademarks of Skyworks Solutions, Inc., in the United States and other countries. Third-party brands and names are for
identification purposes only, and are the property of their respective owners. Additional information, including relevant terms and conditions, posted at www.skyworksinc.com, are incorporated by reference.
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17