202062A.pdf

DATA SHEET
AAT2215
High Current Synchronous Step-Up Regulator
with Programmable Current Limit
General Description
Features
The AAT2215 SwitchReg™ is a high current, synchronous
step-up converter with a programmable peak NMOS current limit. It is ideal to prevent the input current from
overloading the system power in PC Card GSM/GPRS/3G
and WiMax modem card applications. The AAT2215's
internal compensation is optimized for the large bulk
tantalum output capacitors needed to support the output
voltage during large load pulses.
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•
•
•
•
•
The output voltage may be programmed from 3.0V to
5.5V by external resistor divider. Light load switching
frequency modulation and low quiescent current maintain high efficiency performance for light load mode
conditions.
•
•
•
•
•
•
•
•
Two current limits are designed into the AAT2215. One is
the low-side power MOSFET programmable peak current
limit, which works when the device is in step-up regulation state. An external resistor is used to program the
current limit from 600mA to 4.0A. The other is the highside current limit, which operates in a linear mode to
limit inrush current to 750mA when the output charges
up to the input voltage. The AAT2215 includes internal
over-voltage protection and a system ready signal.
2.4V to VOUT + 0.25V Input Voltage Range
Adjustable 3.0V to 5.5V Output Voltage
Internal Compensation
600kHz Switching Frequency
Programmable Peak NMOS Current Limit
(0.6A to 4.0A)
Synchronous P-Channel MOSFET
▪ True Load Disconnect in Shutdown
▪ Reverse Current Block When Enabled
▪ Start-Up Inrush Current Limit (0.75A) and Overload
Current Limit (3A)
Up to 95% Efficiency
Active-Low Power Ready Indicator (RDY)
Very Low 55μA No-Load Operating Current
Less than 1μA Shutdown Current
6V Output Over-Voltage Protection (OVP)
Thermal Shutdown Protection (TSHDN)
Short Circuit Protection
Low-Profile TDFN33-12 Package
Applications
•
•
•
•
•
The AAT2215 is available in a Pb-free, 3mm x 3mm,
12-pin TDFN package (TDFN33-12) rated from -40°C to
+85°C.
Media Tablets
PCI-Express Cards
PCMCIA Cards
Modems
Wireless Data Cards
Typical Application Figure
L1 2.2μH
VIN
2.4V to VOUT + 0.25V
IN
RRDY
100kΩ
CIN
10μF
VOUT
3.8V
LX
OUT
AAT2215
RDY
RFB1
536kΩ
COUT
22μF
FB
ON
OFF
RFB2
100kΩ
EN
RSET
100kΩ
AGND
RSET
PGND
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
1
DATA SHEET
AAT2215
High Current Synchronous Step-Up Regulator
with Programmable Current Limit
Pin Descriptions
Pin
Name
1, 2
LX
3
EN
4
IN
5
RDY
6
AGND
7
FB
8
RSET
9, 10
11, 12
OUT
PGND
EP
Exposed Pad
Function
Inductor switching node. LX is internally connected to the source of the internal low-side N-channel
MOSFET (NMOS), and synchronous high-side P-channel MOSFET (PMOS). Externally connected to the
switching side of the power inductor as shown in the Typical Application drawing.
Enable input. A logic high enables the AAT2215 regulator. A logic low forces the AAT2215 into shutdown mode, placing the output into a high-impedance state (true load disconnect) and reducing the
quiescent current to less than 1μA.
Input supply. IN powers the analog control circuitry during start-up. Bypass IN to GND with a 10μF or
greater ceramic capacitor.
Power ready signal (active low). RDY is an open-drain, active-low output. RDY is pulled low when the
feedback voltage exceeds 95% of the target voltage.
Analog ground. AGND is internally connected to the analog ground of the control circuitry.
Feedback input. FB senses the output voltage for regulation control. For adjustable output versions,
connect a resistive divider network from the output to FB to GND to set the output voltage accordingly.
The FB regulation threshold is 0.6V.
Programmable current-limit control. Connect an external resistor between RSET and AGND to set the
peak NMOS current-limit threshold. The current-limit threshold may be adjusted from 0.6A to 4.0A.9
Output of step-up regulator. OUT internally connects to the synchronous high-side P-channel MOSFET.
Power ground. PGND is internally connected to the source of the low-side N-channel MOSFET.
Substrate/thermal ground. The exposed pad is internally connected to the substrate of the controller,
and provides the lowest thermal impedance between the regulator and the PCB. Connect the exposed
pad directly to the ground plane to reduce thermal stress.
Pin Configuration
TDFN33-12
(Top View)
LX
LX
EN
IN
RDY
AGND
2
1
12
2
11
3
10
4
9
5
8
6
7
PGND
PGND
OUT
OUT
RSET
FB
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
DATA SHEET
AAT2215
High Current Synchronous Step-Up Regulator
with Programmable Current Limit
Absolute Maximum Ratings1
Symbol
VIN
VOUT, VLX
VEN
VFB
VRDY
VGND
TJ
TS
TLEAD
Description
IN to PGND
OUT, LX to PGND2
EN to AGND
FB to AGND
RDY to AGND
AGND to PGND
Junction Temperature Range
Storage Temperature Range
Maximum Soldering Temperature (at leads, 10 sec.)
Value
-0.3 to 6
-0.3 to 6
-0.3 to 6
-0.3 to 6
-0.3 to 6
-0.3 to 0.3
-40 to 150
-65 to 150
300
Units
V
°C
Thermal Characteristics3
Symbol
Description
TDFN33-12 Thermal Impedance
θJA
Maximum Junction-to-Ambient Thermal Resistance
PD
Maximum Power Dissipation4
Value
Units
50
2
°C/W
W
Value
Units
-40 to 85
2.4 to VOUT + 0.25
3.0 to 5.5
°C
Operating Characteristics
Symbol
TA
VIN
VOUT
Description
Operating Ambient Temperature Range
Input Voltage Range
Output Voltage Range
V
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.
2. The P-channel between LX and OUT that changes the substrate connection to control the body diode. This allows the high-side diode when the regulator is active, but allows
the output to be isolated from the input during shutdown (true load disconnect).
3. Mounted on 1.6mm thick FR4 board.
4. Derate 25mW/°C above 25°C.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
3
DATA SHEET
AAT2215
High Current Synchronous Step-Up Regulator
with Programmable Current Limit
Electrical Characteristics
VIN = 3.3V, VOUT = 3.8V, AGND = PGND. TA = +25°C, unless otherwise noted.
Symbol
VIN
VIN(MIN)
VOUT
VUVLO
IQ
ISHDN
Description
Input Voltage Range
Minimum Start-Up Voltage
Output Voltage Range
Input Under-Voltage Lockout
Supply Current with No Load
Shutdown Current
VFB
FB Accuracy
IFB
FB Leakage Current
ΔVOUT/IOUT
Load Regulation
ΔVOUT/VIN
VOVP
fOSC
DMAX
tON(MIN)
RON(PMOS)
RON(NMOS)
ISTRT
ILIM(PMOS)
Line Regulation
OUT Over-Voltage Protection Threshold
Oscillator Frequency
Maximum Duty Cycle
Minimum On-Time
High-Side P-Channel On-Resistance
Low-Side N-Channel On-Resistance
Input Start-Up PMOS Inrush Current Limit
PMOS Linear Overload Current Limit
ILIMPK
Low-Side Peak Current Limit Threshold
Enable, Power Ready and Start-Up Features
VEN(H)
Logic Input Threshold High for EN
Logic Input Threshold Low for EN
VEN(L)
IEN
EN Input Current
VRDY
Power Ready Threshold
RRDY
RDY On-Resistance
Thermal
TSD
Over-Temperature Shutdown Threshold
Over-Temperature Shutdown Hysteresis
TSD(HYS)
4
Conditions
Min
Typ
2.4
2.3
VIN Rising, Hysteresis = 0.1V
No Load Current; Not Switching
EN = GND, VIN = 5.5V
TA = 25°C, IOUT = 10mA
TA = -40°C to 85°C, IOUT = 10mA
VFB = 0 to 1.0V
VIN = 3.3V, VOUT = 3.8V, 0 to 2.5A
Load
VIN = 2.4V to VOUT, IOUT = 10mA
Hysteresis = 200mV
VOUT + 0.5V < VIN, RLOAD = 1Ω
VOUT = 0V
RSET = 75kΩ, TA = 25°C
RSET = 63.4kΩ, TA = 25°C
RSET = 1000kΩ, TA = 25°C
3.0
1.9
0.588
0.582
-0.2
2.1
55
0.60
0.60
Max
VOUT +
0.25
2.4
5.5
2.3
80
1
0.612
0618
+0.2
1
5.6
480
0.5
2.625
0.3
6.0
600
90
80
70
90
0.75
3.0
3.5
4.0
0.6
6.4
720
Temperature Rising
4.375
95
2700
150
15
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
μA
V
μA
%/V
V
kHz
%
ns
mΩ
0.4
+1.0
-1.0
V
%/A
1.4
VEN = GND or 5.5V
FB Rising, Hysteresis = 10%
VFB = 0.62V, ISINK = 10μA
Units
A
V
μA
%
Ω
°C
DATA SHEET
AAT2215
High Current Synchronous Step-Up Regulator
with Programmable Current Limit
No Load Quiescent Current vs Input Voltage
No Load Quiescent Current vs Temperture
(Close Loop,VOUT = 3.8V)
(Close Loop,VIN = 3.3V, VOUT = 3.8V)
180
330
Quiescent Current (μA)
Quiescent Current (μA)
360
300
270
240
210
180
25°C
150
85°C
120
-40°C
90
165
150
135
120
105
90
2.4
2.5
2.6
2.7
2.8
2.9
3
3.1
3.2
3.3
-40
-15
Input Voltage (V)
No Load Quiescent Current vs Input Voltage
35
60
85
No Load Quiescent Current vs Temperature
(Open Loop)
(Open Loop, VIN = 3.3V)
50
50
48
46
44
42
25°C
40
85°C
38
-40°C
Quiescent Current (μA)
Quiescent Current (μA)
10
Temperature (°C)
36
48
46
44
42
40
38
36
2.4
2.5
2.6
2.7
2.8
2.9
3
3.1
3.2
3.3
-40
-15
Input Voltage (V)
10
35
60
85
Temperature (°C)
Frequency vs Temperature
Enable Threshold vs Input Voltage
1.2
1.1
620
1.0
600
VEN (V)
Frequency (Khz)
640
580
560
0.9
0.8
540
VENH
0.7
520
VENL
500
0.6
-40
-15
10
35
Temperature (°C)
60
85
2.4
2.7
3
3.3
3.6
3.9
4.2
4.5
4.8
5.1
Input voltage (V)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
5
DATA SHEET
AAT2215
High Current Synchronous Step-Up Regulator
with Programmable Current Limit
Enable Threshold vs Temperature
Feedback Voltage vs Input Voltage
1.2
0.609
VENH
1.1
0.606
VENL
0.603
VFB (V)
VEN (V)
1.0
0.9
0.8
0.600
0.597
0.7
0.594
0.6
-40
-15
10
35
60
0.591
85
2.4
2.7
3
3.3
Temperature (°C)
3.6
3.9
4.2
4.5
4.8
5.1
Input Voltage (V)
Feedback Voltage vs Temperature
Efficiency
(L = 2.2μH, VOUT = 3.8V)
100
0.609
90
0.606
Efficiency (%)
80
VFB (V)
0.603
0.600
0.597
0.594
0.591
70
60
50
VIN = 2.4V
40
VIN = 2.7V
30
20
VIN = 3.0V
10
VIN = 3.3V
0
-40
-15
10
35
60
85
0.1
1.0
Temperature (°C)
10.0
100.0
Efficiency
Load Regulation
(L = 2.2μH, VOUT = 5.0V)
(L = 2.2μH, VOUT = 5.0V)
0.9
VIN = 2.4V
90
0.7
Output Error (%)
80
Efficiency (%)
10000.0
Output Current (mA)
100
70
60
VIN = 2.4V
50
VIN = 2.7V
40
VIN = 3.0V
30
20
VIN = 3.3V
10
VIN = 4.2V
VIN = 2.7V
VIN = 3.0V
0.5
VIN = 3.3V
0.3
VIN = 4.2V
0.1
-0.1
0
0.1
1.0
10.0
100.0
Output Current (mA)
6
1000.0
1000.0
10000.0
-0.3
0.0
0.1
1.0
10.0
100.0
1000.0
Output Current (mA)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
10000.0
DATA SHEET
AAT2215
High Current Synchronous Step-Up Regulator
with Programmable Current Limit
Load Regulation
Line Regulation
(L = 2.2μH, VOUT = 3.8V)
(L = 2.2μH, VOUT = 3.8V)
0.6
0.5
VIN = 2.4V
VIN = 3.0V
0.2
IOUT = 1mA
0.4
VIN = 2.7V
Output Error (%)
Output Error (%)
0.4
VIN = 3.3V
0.0
-0.2
-0.4
IOUT = 100mA
0.3
IOUT = 500mA
0.2
IOUT = 1000mA
0.1
IOUT = 1500mA
0.0
-0.1
-0.2
-0.3
-0.4
-0.6
0.0
0.1
1.0
10.0
100.0
1000.0
10000.0
-0.5
2.4
2.5
Output Current (mA)
2.6
2.7
2.8
2.9
3.0
3.1
3.2
3.3
Input Voltage (V)
Soft Start
Output Voltage Ripple
(VOUT = 3.8V; VIN = 3.3V; IOUT = 0A)
(VIN = 3.3V; VOUT = 3.8V; l = 2.2μH; IOUT = 0mA)
VOUT (AC)
(20mV/div)
0V
VEN
(1V/div) 0V
VOUT
(1V/div)
0V
IL
(0.5A/div)
IIN
0A
(0.5A/div)
0A
Time (100μs/div)
Time (400μs/div)
Output Voltage Ripple
Output Voltage Ripple
(VIN = 3.3V; VOUT = 3.8V; L = 2.2μH; IOUT = 1A)
(VIN = 3.3V; VOUT = 3.8V; L = 2.2μH; IOUT = 2.5A)
VOUT (AC)
(100mV/div)
0V
0V
VOUT (AC)
(20mV/div)
IL
(1.0A/div)
IL
(0.5A/div)
0A
0A
Time (800ns/div)
Time (800ns/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
7
DATA SHEET
AAT2215
High Current Synchronous Step-Up Regulator
with Programmable Current Limit
Load Transient
Load Transient
(VOUT = 3.8V; VIN = 3.3V; IOUT = 100mA to 1.2A;
L = 2.2μH; COUT = 22μF + 220μF)
(VOUT = 3.8V; VIN = 3.3V; L = 2.2μH;
IOUT = 100mA to 2.5A; COUT = 22μF + 220μF)
VOUT (AC) 0V
(500mV/div)
VOUT (AC) 0V
(200mV/div)
2.5A
IOUT
0A
(0.5A/div)
IOUT
0A
(1A/div)
100mA
Time (400μs/div)
100mA
Time (400μs/div)
Line Transient Response
(VIN = 2.7V to 3.3V; VOUT = 3.8V; L = 2.2μH;
IOUT = 100mA; COUT= 22μF)
VOUT (AC)
0V
(100mV/div)
3.3V
VIN
(0.6V/div)
2.7V
Time (400μs/div)
8
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
DATA SHEET
AAT2215
High Current Synchronous Step-Up Regulator
with Programmable Current Limit
Functional Block Diagram
OUT
IN
UVLO
Over-Temperature
Protection
Internal Power
Select
Control Logic
DH
Reverse
Current Block
When Enabled
True Load
Disconnect
PMOS
Current
Control
Mode
Control
OVP
EN
NMOS
Current
Control
RSET
PMOS
Comp
OUT
LX
6.0V
RDY
0.6V
NMOS
DL
PGND
0.575V
Slope
Compensation
Error
Amp.
FB
AGND
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
9
DATA SHEET
AAT2215
High Current Synchronous Step-Up Regulator
with Programmable Current Limit
Functional Description
The AAT2215 synchronous step-up converter is targeted
for PC Card GSM/GPRS/3G and WiMax modem card
applications. It includes a 0.75A start-up PMOS current
limit to ensure fast, controlled power-up, a 3A overload
PMOS current limit after startup, and a programmable
peak NMOS step-up current limit up to 4A for continuous
step-up operation within the PCMCIA specifications.
The 600kHz switching frequency of the AAT2215 facilitates output filter component size reduction for improved
power density and reduced overall footprint. It also provides greater bandwidth and improved transient response
over other lower frequency step-up converters. The
compensation and feedback is integrated with only three
external components (CIN, COUT, L). Low RDS(ON) synchronous power switches provide high efficiency for heavy
load conditions. Switching frequency modulation and low
quiescent current maintains this high efficiency for light
load mode condition. In addition to the improved efficiency, the synchronous step-up has the added performance advantage of true load disconnect during shutdown (<1μA shutdown current), reverse current blocking when enabled, inrush current limit, and short-circuit
protection.
PWM Control Scheme
with Low-Noise Light-Load
The AAT2215 is a fixed-frequency PWM peak current
mode control step-up converter. For light load condition
(70mA to 80mA and below), the converter stays in a
variable frequency (Light Load) mode to reduce the
dominant switching losses. In addition to Light Load
operation, a zero current comparator blocks reverse current in the P-channel synchronous MOSFET, forcing DCM
operation at light load. These controls, along with very
low quiescent current, help to maintain high efficiency
over the complete load range without increased output
voltage ripple during light load conditions.
Shutdown and True Load Disconnect
A typical synchronous step-up (step-up) converter has a
conduction path from the input to the output via the
parasitic body diode of the P-channel MOSFET when the
converter shuts down. The AAT2215 design a special
power selection for the substrate to keep the parasitic
body diode in off-state during shutdown and startup. This
enables the AAT2215 to provide true load disconnect during shutdown and PMOS inrush current limit at startup.
10
During the initial PMOS linear mode start-up period, the
start-up control circuitry is powered by the input supply
pin. When the output voltage of the AAT2215 enters
step-up mode (VIN ≈ VOUT), the step-up control circuitry
draws power directly from the output supply to ensure
sufficient voltage head-room.
When EN is set to logic low, the step-up converter is
forced into shutdown state with less than 1μA input current.
Soft-start and PMOS
Current Limit Protection
Start-Up Inrush Current Protection
When initially powering up, the load disconnect feature
allows the output voltage to be less than the input voltage. In order to avoid large surge current when the
regulator is enabled, the AAT2215 operates the synchronous P-channel MOSFET in a current-limited linear mode
to softly charge the large output capacitor. This linear
start-up feature effectively limits the input current to
0.75A until the output voltage exceeds the input voltage.
After VOUT exceeds VIN, the regulator switches the body
diode connection and begins step-up operation.
Overload Current-Limit Protection
Once start-up is completed, (RDY is pulled low), the
AAT2215 increases the PMOS overload current-limit
threshold to 3A. If the output is overloaded, causing VOUT
to drop below VIN by 210mV, the regulator will switch
back to a linear operating mode. This activates the 3A
PMOS overload current protection and the AAT2215 will
reverse the body-diode connection. This effectively limits
the output current under such fault conditions.
Combined with the thermal shutdown protection, the
PMOS current-limit protects the regulator against overload and short-circuit fault conditions.
The overload current limit is fixed at 3A, and short-circuit
protection also adopts this 3A current limit; the 3A current limit is not changed with RSET value.
Programmable Peak NMOS Current-Limit
When the output voltage of the AAT2215 enters step-up
mode (VIN < VOUT), the NMOS starts switching and the
NMOS peak current-limit becomes active. During the
inductor charge cycle, the low-side NMOS turns on and
the AAT2215 monitors the current through the NMOS. If
the current exceeds the current-limit threshold set by
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
DATA SHEET
AAT2215
High Current Synchronous Step-Up Regulator
with Programmable Current Limit
the RSET resistor, the regulator immediately turns off the
low-side NMOS. The regulator limits the instantaneous
peak inductor/NMOS current, so the current-limit threshold must be set high enough to support the desired output current.
Power Ready
To indicate the output voltage is in regulation, an activelow open-drain output pin (RDY) pulls down when the
feedback voltage is above 95% of the nominal regulation
voltage level. RDY becomes a high-impedance output if
the feedback voltage drops below 85% of the nominal
regulation voltage level.
Application Information
RSET Selection for
Programmable Current Limit
The current limit of the internal low-side NMOS power
switch is programmable from 0.6A to 4.0A by an external resistor connected from RSET to ground.
When the inductor’s peak current reaches the current
limit, the RDY indicator is pulled high. Table 1 gives standard 1% standard metal film resistor example values for
the peak NMOS current-limit programming.
Over-Voltage Protection
The AAT2215’s over-voltage protection function prevents
the output voltage from exceeding the fixed 6V (typ)
over-voltage point, which would exceed the absolute
maximum rating of the regulator. If OUT exceeds 6V, the
regulator will stop switching until the output voltage
drops below 5.8V (200mV hysteresis) and FB is below its
regulation threshold.
When the junction temperature exceeds the over-temperature threshold, the AAT2215 thermal protection circuitry shuts down the regulator. Thermal shutdown disables switching and PMOS current limit is functional to
control the current flowing through to avoid any damage
of the step-up converter. When the over-temperature
fault condition is removed, the step-up recovers regulation automatically.
ILIMIT (A)
63.4
75.0
82.0
100.0
118.0
150.0
180.0
300.0
432.0
1000.0
4
3.48
3.1
2.6
2.15
1.75
1.52
1.02
0.82
0.6
Table 1: Examples of 1% Standard Resistor
Value of RSET
4.5
4
3.5
3
ILIMIT (A)
Thermal Shutdown
RSET (kΩ)
2.5
2
1.5
1
0.5
0
0
100
200
300
400
500
600
700
800
900
1000
Resistance (kΩ)
Figure 1: ILIMIT vs RSET
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11
DATA SHEET
AAT2215
High Current Synchronous Step-Up Regulator
with Programmable Current Limit
Output Voltage Programming
Input Capacitor
The output voltage of the AAT2215 may be programmed
from 3.0V to 5.5V with an external resistive voltage
divider. Resistors R1 and R2 in Figure 1 program the
output voltage as shown by the following equation:
Select a low ESR ceramic capacitor with a value of at
least 10μF as the input capacitor. Place the input capacitor as close to the IN and PGND pins as possible in order
to minimize the stray resistance from the converter to
the input power source.
R1 =
VOUT
VREF - 1 · R2
where 0.6V is the feedback reference voltage (VREF). To
limit the bias current required for the external feedback
resistor string while maintaining good noise immunity,
the suggested value for R2 is 100kΩ. Table 2 summarizes the resistor values with R2 set to 100kΩ for good
noise immunity and 6μA increased load current and
gives some 1% standard metal film resistor values for
R1 at different output voltage settings.
VOUT(V)
R2 = 100kΩ
R1 = (kΩ)
3
3.3
3.6
3.8
4.2
4.5
5
5.5
400
450
500
536
600
650
733
816
Table 2: Resistor Selection for Output Voltage
Inductor Selection
The AAT2215 is designed to operate with a 2.2μH inductor for all input/output voltage combinations. For high
efficiency, choose a ferrite inductor with a high frequency core material to reduce core losses. The inductor
should have low ESR (equivalent series resistance) to
reduce the I2R losses, and must be able to handle the
peak inductor current without saturating. To minimize
radiated noise, use a shielded inductor.
12
Output Capacitor
The output capacitor provides energy to the load when
the high-side MOSFET is switched off. The output capacitance together with the boost switching frequency, duty
cycle, and load current value determine the capacitive
output voltage ripple when the boost operation is in the
continuous PWM state.
IOUT · D
∆VOUT = C
OUT · fSW
where D is the duty ratio of low-side MOSFET turn-on
time divided by the switching period. It is calculated
using the equation:
D=1-
VIN
VOUT
The output capacitor’s ESR increases the output ripple by
IOUT · ESR. The total output ripple is:
IOUT · D
∆VOUT = (IOUT · ESR) + C
OUT · fSW
So the minimum recommended output capacitor value
may be determined by:
1
IOUT · D
COUT ≥ ∆V
· f
OUT - (IOUT · ESR)
SW
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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DATA SHEET
AAT2215
High Current Synchronous Step-Up Regulator
with Programmable Current Limit
High Load Pulse Application
Together with a large value output capacitor or supercap,
the AAT2215 can support a higher load pulse in lower
input current limited applications such as GSM burst
mode in WCDMA, Edge, GPRS and TD-SCDMA applications. The large capacitance is determined by NMOS
peak current limit, inductor current ripple, VIN, VOUT, load
pulse high current level and elapsed time. The capacitor
value can be calculated using the following three steps
as follows:
TON is 577μs for a 217Hz 12.5% duty cycle load pulse.
Considering 20% capacitance tolerance, the minimum
capacitance should be 220μF. Figure 2 shows the
AAT2215 operating waveform under a 2.0A 577μs load
pulse with 220μF tantalum capacitor as COUT, as well as
a 22μF ceramic capacitor to closely filter the output voltage.
Load Pulse Response
5.00
4.50
Output Voltage
(0.5V/div) (top)
V · I ·η
IOUT_BOOST = IN LIM
VOUT
4.00
3.50
2.50
Finally, derive the COUT at a certain load-on period TON:
COUT =
I COUT ∙ TON
∆VOUT
To consider the real tantalum capacitor having 20% tolerance, the selected capacitance should be 20% higher
than the calculated value. Example: A 2.0A, 217Hz
12.5% duty cycle load pulse is applied on 3.8V VOUT at
3.3V VIN. An input peak current limit of 2.4A and a VOUT
drop of less than 450mV are required. Under these conditions, with 89% efficiency, the AAT2215's output current is
I OUT _ BOOST =
3.3·2.4·89%
= 1.86A
3.8
The maximum current necessary for the large capacitor
value is:
2
ILOAD
1
0
Second, calculate the maximum current the large capacitor COUT should provide:
I COUT = I LOAD _ PEAK - I OUT _ BOOST
VOUT
3.00
Output Current
(0.5A/div) (bottom)
First calculate the AAT2215's load-on current from the
expected ILIM. Assume the input current equals ILIM
because the inductor current ripple is low enough when
compared to the input current:
Time (800μs/div)
Figure 2: AAT2215 Operation Waveform When
2.0A 217Hz 577μs Load Pulse is Applied.
Layout Guidance
For best performance of the AAT2215, the following
guidelines should be followed when designing the PCB
layout:
1.
Make the power trace as short and wide as possible,
including the input/output power lines and switching
node, etc.
2. Connect the analog and power grounds together with
a single short line and connect all low current loop
grounds to analog ground to decrease the power
ground noise on the analog ground and achieve better load regulation.
3. For good power dissipation, connect the exposed pad
under the package to the top and bottom ground
planes by PCB pads.
I COUT = 2.0 - 1.86 = 0.14A
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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13
DATA SHEET
AAT2215
High Current Synchronous Step-Up Regulator
with Programmable Current Limit
Schematic and Layout
R4 (opt)
C4 (opt)
LX
U1 AAT2215
C1
10μF
OUT
OUT
FB
RSET
AGND
EP
6
PGND
0
VIN
GND
12
11
10
R3
100k
JP1
PGND
VOUT
3.8V
9
C21
22μF
7
8
RDY
VIN
VIN
PGND
R1
536k
RSET
100k
5
L1 2.2μH
1 LX
2
LX
4
VIN
3
EN
VIN
C22
220μF
C3
(open)
R2
100k
AGND
RDY
Figure 3: AAT2215 Evaluation Board Schematic.
Figure 4: AAT2215 Evaluation Board
Top Side Layout.
14
Figure 5: AAT2215 Evaluation Board
Bottom Side Layout.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
DATA SHEET
AAT2215
High Current Synchronous Step-Up Regulator
with Programmable Current Limit
Part Number
Inductance
(μH)
Max DC Current
(A)
DCR (mΩ)
Size LxWxH
(mm)
Type
CHRH103RNP-2R2NC
CDRH103RNP-3R3NC
7440650033
LQH6PPN3R3N43
2.2
3.3
3.3
3.3
6.7
5.5
4.7
4.5
20
21
20
16
10x10x2.8
10x10x2.8
10x10x2.8
6x6x4.3
Shielded
Shielded
Shielded
Shielded
Table 3: Surface Mount Inductors.
Part Number
AAT2215IWP-0.6
RC0603FR-07536KL
RC0603FR-07100KL
RC0603FR-07100KL
RC0603FR-07100KL
GRM21BR61C106K
GRM21BR60J226M
TPSY227M006R0150
CDRH103RNP-2R2NC
Description
High Current Step-Up Converter with
Adjustable Current Limit
Res 536kΩ 1/10W 1% 0603 SMD
Res 100kΩ 1/10W 1% 0603 SMD
Res 100kΩ 1/10W 1% 0603 SMD
Res 100kΩ 1/10W 1% 0603 SMD
Cap Ceramic 10μF 0805 X5R 16V 10%
Cap Ceramic 22μF 0805 X5R 6.3V 20%
Cap Tan 220μF case 6.3V 20%
Inductor 2.2μH 6.7A SMD
Manufacturer
Skyworks
Yageo
Murata
AVX
Sumida
Table 4: AAT2215 Evaluation Board Bill of Materials.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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15
DATA SHEET
AAT2215
High Current Synchronous Step-Up Regulator
with Programmable Current Limit
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
TDFN33-12
P5XYY
AAT2215IWP -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
TDFN33-12
Index Area
0.40 ± 0.05
Detail "A"
C0.3
0.45 ± 0.05
2.40 ± 0.05
3.00 ± 0.05
0.1 REF
3.00 ± 0.05
1.70 ± 0.05
Top View
Bottom View
0.23 ± 0.05
Pin 1 Indicator
(optional)
0.05 ± 0.05
0.23 ± 0.05
0.75 ± 0.05
Detail "A"
Side View
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
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202062A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 14, 2012
DATA SHEET
AAT2215
High Current Synchronous Step-Up Regulator
with Programmable Current Limit
Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.
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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
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Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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