Analogic AAT1232 24v 100ma step-up converter Datasheet

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, AnalogicTech’s
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, thermallyenhanced 16-pin 3x4mm TDFN low-profile package or a Pb-free 12-pin TSOPJW package.
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SwitchReg™
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
VP
C1
2.2μF
D1
Schottky
24V @ 100mA
LIN
VIN
AAT1232
SW
PGND
R1
576kΩ
C2
2.2μF, 25V
FB1
R2
10.0kΩ
EN/SET
FB2
SEL
1232.2007.06.1.5
GND
R3
20.0kΩ
1
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
6, 7
12
11
9, 10
VIN
N/C
SW
8
6, 7, 8
PGND
9
10
5
4
GND
FB2
11
3
FB1
12
N/A
1, 2
EP
LIN
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
1232.2007.06.1.5
AAT1232
24V 100mA Step-Up Converter
Absolute Maximum Ratings1
TA = 25°C, unless otherwise noted.
Symbol
VIN, VP
SW
LIN, EN/SET,
SEL, FB1, FB2
TJ
TS
TLEAD
Description
Value
Units
Input Voltage
Switching Node
-0.3 to 6.0
28
V
V
Maximum Rating
VIN + 0.3
V
-40 to 150
-65 to 150
300
°C
°C
°C
Value
Units
Operating Temperature Range
Storage Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
Recommended Operating Conditions
Symbol
Description
θJA
Thermal Resistance
PD
Maximum Power Dissipation (TA = 25ºC)
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.
1232.2007.06.1.5
3
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
Power Supply
VIN
VOUT(MAX)
VUVLO
IQ
Description
Input Voltage Range
Maximum Output Voltage
UVLO Threshold
Quiescent Current
ISHDN
IOUT
VIN Pin Shutdown Current
Output Current
FB1
FB1 Reference Voltage
FB2
FB2 Reference Voltage
ΔVLOADREG
ΔVLINEREG/ΔVIN
RDS(ON)L
RDS(ON)IN
TSS
TSD
THYS
ILIM
SEL, EN/SET
VSEL(L)
VSEL(H)
VEN/SET(L)
VEN/SET(H)
TEN/SET LO
TEN/SET HI MIN
TEN/SET HI MAX
TOFF
TLAT
IEN/SET
Conditions
Load Regulation
Line Regulation
Low Side Switch On Resistance
Input Disconnect Switch
On Resistance
Soft-Start Time
Over-Temperature Shutdown
Threshold
Shutdown Hysteresis
N-Channel Current Limit
SEL Threshold Low
SEL Threshold High
Enable Threshold Low
Enable Threshold High
EN/SET Low Time
Minimum EN/SET High Time
Maximum EN/SET High Time
EN/SET Off Timeout
EN/SET Latch Timeout
EN/SET Input Leakage
Min
Typ
2.7
VIN Rising
Hysteresis
VIN Falling
SEL = GND, VOUT = 18V,
IOUT = 0, R3 = 20kΩ2, 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 = 20kΩ3
VIN = 2.7V to 5.5V, R3 = 20kΩ3
2.7V
5.5V
2.7V
5.5V
5.5
24
2.7
V
V
V
mV
V
150
0.3
40
mA
70
µA
1.0
100
µA
mA
1.164
1.2
1.236
V
0.582
0.6
0.618
V
VIN = 3.6V
=
=
=
=
Units
1.8
From Enable to Output
Regulation; VOUT = 15V
VIN
VIN
VIN
VIN
Max
0.02
0.6
0.08
%/mA
%/V
Ω
0.18
Ω
0.35
ms
140
°C
15
3.0
°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.
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1232.2007.06.1.5
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)
Output Error (%)
Efficiency (%)
(VOUT = 20V; R3 = 20kΩ
Ω)
1.5
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 = 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
VIN = 3.6V
50
40
30
VIN = 4.2V
VIN = 5V
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)
1232.2007.06.1.5
100
0.1
1
10
100
Output Current (mA)
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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
0.36
1.1
Supply Current (mA)
Supply Current (mA)
1.2
0.32
0.28
0.24
0.2
0.16
0.12
4.5
5
0.9
0.8
0.6
0.5
0.3
0.2
0.0
-40
0.08
4
5.5
10
35
60
Output Ripple
Output Ripple
(VIN = 4.2V; VOUT = 18V; IOUT = 100mA)
(VIN = 4.2V; VOUT = 18V; No Load)
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
17.0
-1.0
17.0
-0.2
Time (500ns/div)
Output Voltage
(top) (V)
5.0
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)
0.4
3.5
60
No Load Input Current vs. Temperature
(VOUT = 18V; EN_High)
3
35
Temperature (°°C)
Input Voltage (V)
2.5
10
Time (100µs/div)
1232.2007.06.1.5
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
4
4.5
5
5.5
6
Input Voltage (V)
100°C
100
80
25°C
60
85°C
3.5
120°C
120
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)
1232.2007.06.1.5
7
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.
1232.2007.06.1.5
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.
1232.2007.06.1.5
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 high-speed 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 builtin 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 10kΩ 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.
9
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
Selecting DC/DC Boost 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.
10
Minimum 6.3V rated ceramic capacitors are required
at the input. Ceramic capacitors sized as small as
0603 are available which meet these requirements.
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). Aluminum-electrolytic 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.
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 (θJA) 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
1232.2007.06.1.5
AAT1232
24V 100mA Step-Up Converter
diodes are recommended for outputs less than 15V,
while 30V rated Schottky diodes are recommended
for outputs greater than 15V.
The average diode current is equal to the output
current.
IAVG = IOUT
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.
The average output current multiplied by the forward diode voltage determines the loss of the output diode.
PLOSS_DIODE = IAVG · VF
= IOUT · VF
D=
TON
TON + TOFF
= TON ⋅ FS
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)).
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 θJA 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.
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.
1232.2007.06.1.5
DMAX =
(VOUT + VF - VIN(MIN))
(VOUT + VF)
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.
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 worst-case RMS conditions, the current
waveform is critically continuous. The resulting
11
AAT1232
24V 100mA Step-Up Converter
RMS calculation yields worst-case 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
To ensure high reliability, the inductor temperature
should not exceed 100ºC. 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
12
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 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.
1232.2007.06.1.5
AAT1232
24V 100mA Step-Up Converter
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
R3 = 4.99kΩ
R3 = 20.0kΩ
Table 1: SEL Pin Voltage Control Resistor Values (1% resistor tolerance).
S2Cwire Serial Interface
2
AnalogicTech's S Cwire serial interface is a proprietary high-speed single-wire interface available
only from AnalogicTech. 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
1232.2007.06.1.5
register is reset to the default value, which sets the
FB2 pin to 0.6V if EN is subsequently pulled high.
EN/SET
Rising
Edges
FB2
Reference
Voltage (V)
EN/SET
Rising
Edges
FB2
Reference
Voltage (V)
1
2
3
4
5
6
7
8
0.60 (Default)
0.64
0.68
0.72
0.76
0.80
0.84
0.88
9
10
11
12
13
14
15
16
0.92
0.96
1.00
1.04
1.08
1.12
1.16
1.20
Table 2: S2Cwire Voltage Control Settings
(SEL = Low).
13
AAT1232
24V 100mA Step-Up Converter
THI
TLO
TOFF
T LAT
EN/SET
1
Data Reg
2
n-1
n ≤ 16
0
n-1
0
Figure 3: S2Cwire Timing Diagram to Program the Output Voltage.
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 setpoint. Upon power up with the SEL pin low and
prior to S2Cwire programming, the default feedback reference voltage is set to 0.6V.
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.
A suggested PCB layout for the AAT1232 boost
converter is shown in Figures 4 and 5. The following PCB layout guidelines should be considered:
14
1. 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.
2. Place the feedback resistors close to the output
terminals. Route the output pin directly to resistor R1 to maintain good output regulation. R3
should be routed close to the output GND pin.
3. Minimize the distance between L1 to D1 and
switching pin SW; minimize the size of the PCB
area connected to the SW pin.
4. Maintain a ground plane and connect to the IC
RTN pin(s) as well as the GND terminals of C1
and C2.
5. Consider additional PCB area on D1 cathode
to maximize heatsinking capability. This may
be necessary when using a diode with a high
thermal resistance.
6. When using the TDFN34-16 package, connect
paddle to SW pin or leave floating. Do not connect to RTN/GND conductors.
7. To avoid problems at startup, add a 10kΩ 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.
1232.2007.06.1.5
AAT1232
24V 100mA Step-Up Converter
Figure 4: AAT1232 Evaluation Board
Top Side.
1232.2007.06.1.5
Figure 5: AAT1232 Evaluation Board
Bottom Side.
15
AAT1232
24V 100mA Step-Up Converter
Manufacturer
Part Number
Rated IF(AV)
Current (A)1
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
Rated
Voltage (V)
Thermal
Resistance
(θJA, °C/W)1
Case
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
Sumida
Sumida
Sumida
Murata
Murata
Taiyo Yuden
Taiyo Yuden
Coiltronics
Coiltronics
Coiltronics
Part Number
Inductance
(µH)
Max DC ISAT
Current (A)
DCR
(Ω)
Size (mm)
LxWxH
Type
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
Murata
Murata
Murata
Murata
Murata
GRM188R60J475KE19D
GRM188R61A225KE34D
GRM188R61C225KA88
GRM21BR61E225KA12L
GRM188R61E105KA12D
Type
Value
(µF)
Voltage
(V)
Temp. Co.
Footprint
LxWxH (mm)
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.
16
1232.2007.06.1.5
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
All AnalogicTech products are offered in Pb-free packaging. The term “Pb-free” means
semiconductor products that are in compliance with current RoHS standards, including
the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more
information, please visit our website at http://www.analogictech.com/pbfree.
Package Information3
TSOPJW-12
2.85 ± 0.20
2.40 ± 0.10
0.10
0.20 +- 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.
1232.2007.06.1.5
17
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.
© Advanced Analogic Technologies, Inc.
AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work
rights, or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice. Except as provided in AnalogicTech’s terms and conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied warranty relating to the sale and/or use of AnalogicTech products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent,
copyright or other intellectual property right. In order to minimize risks associated with the customer’s applications, adequate design and operating safeguards must be provided by the
customer to minimize inherent or procedural hazards. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty.
Specific testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated.
All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085
Phone (408) 737-4600
Fax (408) 737-4611
18
1232.2007.06.1.5