202206A.pdf

DATA SHEET
AAT2608
Single 800mA Switching Converter and Eight-Channel 300mA LDO Regulator
General Description
Features
The AAT2608 is a member of Skyworks' Total Power
Management IC (TPMIC™) product family. It contains an
800mA switching regulator and eight fully integrated
300mA low dropout (LDO) regulators in a small, Pb-free
28-pin 4mmx4mm TQFN package, making it ideal for
space-constrained systems.
• 2.7V to 5.5V Operating Input Voltage Range
• Factory Programmable Outputs from 0.6V to 3.7V
• 800mA Monolithic Switching Converter
• 1.5MHz Switching Frequency
• 90% Efficiency
• 70µA Quiescent Current
• Independent Input Power and Ground
• Independent Enable
• ±1% Typical Accuracy
• 8 Channel 300mA LDO Regulators
• 250mV Dropout Voltage at 250mA
• Low 30µA Quiescent Current
• High PSRR (68dB @10KHZ)
• Independent Enable
• ±1% Typical Accuracy
• Over-Current Protection
• Over-Thermal Protection
• 4mmx4mm, 0.4mm Lead Pitch, 28-pin TQFN Package
The step-down converter is a monolithic synchronous
converter with an integrated compensation network and
90% efficiency. It operates at 1.5MHz and uses a tiny
2.2µH inductor with a small 10µF output capacitor. At no
load the switching converter quiescent current is 70µA.
The 8 channel 300mA LDO regulator features low power
consumption, low dropout, and high noise immunity
from the input power supply. Each channel consumes a
mere 30µA of current when enabled, features 250mV of
dropout at 250mA, and 68dB of power supply rejection
at 10kHz. Each channel uses a small 1µF output capacitor and 2.2µF input capacitor. All regulators include a
separate enable, providing a convenient solution to
implement any power-up and power-down sequencing.
All output voltages are factory One Time Programmable
(OTP) between 0.6V and 3.7V with 100mV increment
and typical regulation accuracy is ±1%. The switcher has
a separate input from the linear regulators, permitting
post-regulation configuration of the LDO channels from
the switcher’s output. Its output is externally programmable with external resistors. LDO1 and LDO2 share the
same input voltage, as do LDO3 and LDO4, while LDO5
through LDO8 have their own independent input.
Applications
• Cellular Application
• Handheld Products
• Media Players (MP4 Players)
• Portable Navigation Devices (PNDs)
The AAT2608 is a safe solution which integrates an overcurrent limit for each channel and over-thermal protection. The device is rated over a temperature range of
-40°C to 85°C.
Typical Application
C7
2.2µF
VINBUCK
VIN34
C1
10µF
C2
2.2µF
VIN8
C6
2.2µF
VCC
U1
AAT2608_TQFN44-28
L1 2.2µH
VCC
ENBUCK
LX
R11
VINBUCK
FBBUCK
R12
VIN34
AAT2608
VIN8
LDO1
ENLD1
ENLD0
PGND AGND
LDO1
Efficiency vs. Output Current
(Buck VOUT = 1.2V)
100
C17
1µF
90
80
C16
10µF
Efficiency (%)
VCC
C15
1µF
70
60
50
40
VIN = 2.7V
VIN = 3.6V
VIN = 4.2V
VIN = 5.5V
30
20
LDO8
LDO8
C8
1µF
10
0
0.1
1
10
100
1000
Output Current (mA)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202206A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 25, 2012
1
DATA SHEET
AAT2608
Single 800mA Switching Converter and Eight-Channel 300mA LDO Regulator
Pin Descriptions
Pin #
Symbol
1
2
3
ENLD3
ENLD2
ENLD1
Function
LDO3 enable; active high.
LDO2 enable; active high.
LDO1 enable; active high.
4
AGND
Analog ground.
5
VIN34
Input to LDO3 and LDO4.
6
VCC
7
LDO1
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
LDO2
LDO3
LDO4
LDO5
LDO6
LDO7
LDO8
VIN8
VIN7
VIN6
VIN5
ENLD8
ENLD7
ENLD6
VINBUCK
LX
PGND
ENLD5
ENLD4
ENBUCK
FBBUCK
Input to power control circuitry for step-down converter, bias, and LDO1 and LDO2. This pin is also the power input for
LDO1 and LDO2.
LDO1 output voltage.
LDO2 output voltage.
LDO3 output voltage.
LDO4 output voltage.
LDO5 output voltage.
LDO6 output voltage.
LDO7 output voltage.
LDO8 output voltage.
Input to LDO8.
Input to LDO7.
Input to LDO6.
Input to LDO5.
LDO8 enable; active high.
LDO7 enable; active high.
LDO6 enable; active high.
Power input to the step-down converter.
Switching node for step-down converter.
Power ground for step-down converter.
LDO5 enable; active high.
LDO4 enable; active high.
Enable for step-down converter; active high.
Feedback input for step-down converter.
Pin Configuration
TQFN44-28
(Top View)
VINBUCK
LX
PGND
ENLD5
ENLD4
ENBUCK
FBBUCK
ENLD3
ENLD2
ENLD1
AGND
VIN34
VCC
LDO1
28
27
26
25
24
23
22
1
21
2
20
3
19
4
18
5
17
6
16
7
15
8
9
10
11
12
13
14
ENLD6
ENLD7
ENLD8
VIN5
VIN6
VIN7
VIN8
LDO8
LDO7
LDO6
LDO5
LDO4
LDO3
LDO2
2
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202206A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 25, 2012
DATA SHEET
AAT2608
Single 800mA Switching Converter and Eight-Channel 300mA LDO Regulator
Absolute Maximum Ratings1
Symbol
Description
VINBUCK, VCC, VIN34, VIN5, VIN6, VIN7, VIN8, ENBUCK, ENLD1, ENLD2,
ENLD3, ENLD4, ENLD5, ENLD6, ENLD7, ENLD8, FBBUCK to AGND
LX to PGND
LDO1, LDO2 to GND
LDO3, LDO4 to GND
LDO5 to GND
LDO6 to GND
LDO7 to GND
LDO8 to GND
PGND to AGND
Value
Units
-0.3 to 6.5
V
-0.3 to VVINBUCK + 0.3
-0.3 to VVCC + 0.3
-0.3 to VVIN34 + 0.3
-0.3 to VVIN5 + 0.3
-0.3 to VVIN6 + 0.3
-0.3 to VVIN7 + 0.3
-0.3 to VVIN8 + 0.3
-0.3 to +0.3
V
Value
Units
50
2
-40 to 150
-65 to 150
300
°C/W
W
V
V
Thermal Information2
Symbol
θJA
PD
TJ
TS
TLEAD
Description
Thermal Resistance
Maximum Power Dissipation
Operating Temperature Range
Storage Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
°C
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.
2. Mounted on an FR4 board.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202206A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 25, 2012
3
DATA SHEET
AAT2608
Single 800mA Switching Converter and Eight-Channel 300mA LDO Regulator
Electrical Characteristics1
VCC = VINBUCK = VIN34 = VIN5 = VIN6 = VIN7 = VIN8 = VINLDO = 5.0V, -40°C ≤ TA ≤ +85°C, unless otherwise noted. Typical
values are TA = 25°C.
Symbol
Description
Conditions
Logic Control / Protection
Input High Threshold
VENLDx
VENBUCK
Input Low Threshold
Step-Down Converter
VINBUCK, VCC Input Voltage Range
IQ
Quiescent Current
ISD
Shutdown Current
VO_STEP-DOWN
VREG
Output Voltage Accuracy
0°C ≤ TA ≤ 85°C
ILIM
P-Channel Current Limit
TRAMP
RDS(ON)H
RDS(ON)L
ΔVOUT /
(VOUT ΔVIN)
FOSC
UVLO
IQ
0.3
V
5.5
V
V
70
µA
1
µA
0.6
80%
of VIN
-3
+3
From device enable to 90% of nominal
output voltage
Time to ramp output voltage from 10% to
90%
%
mA
µs
60
µs
High-Side Switch On-Resistance
Low-Side Switch On-Resistance
260
220
mΩ
mΩ
Line Regulation
0.2
%/V
1.5
2
2.2
MHz
Ramp-Up Time
Oscillator Frequency
Under-Voltage Lockout Threshold
Falling
Rising
2.7
LDO Output Voltage
ILDO = 1mA to 300mA, OTP per requirement
0.6
LDO Accuracy
ILDO = 10mA
VINLDO = 5V, added quiescent current when
LDO is enabled
ILDO = 10mA
ILDO = 1mA to 300mA
VINx = 5V, VOUTx = 1.8V, EN = HIGH, F =
10KHz, ILDO = 100mA
ILDO = 250mA
-3
LDO Quiescent Current
PSRR
Dropout Voltage
LDO Current Limit
Over-Temperature Shutdown Threshold
Over-Temperature Shutdown Hysteresis
V
5.5
VINLDO
- VDO
+3
%
55
µA
30
V
%/V
%/mA
68
dB
250
300
Rising
V
0.1
0.003
145
25
1. Specification over the -40°C to +85°C operating temperature range is assured by design, characterization and correlation with statistical process controls.
4
V
100
Line Regulation
Load Regulation
VDO
ILDO(LIM)
Thermal
TSD
THYS
Units
1000
Low-Dropout Regulators (LDO1-LDO8)
VINLDO
Input Voltage Range
VOUTx
Max
2.7
IOUT = 0mA, device switching, all LDOs
disabled
ENBUCK = 0V
Using external feedback resistors
Startup Time
Typ
1.4
Output Voltage Programmable Range
TSTARTUP
Min
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202206A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 25, 2012
500
mV
mA
°C
°C
DATA SHEET
AAT2608
Single 800mA Switching Converter and Eight-Channel 300mA LDO Regulator
Programming Output Voltages
Programmable Output Voltage Range
Step-down
LDO1
LDO2
LDO3
LDO4
LDO5
LDO6
LDO7
LDO8
0.6V
0.6V
0.6V
0.6V
0.6V
0.6V
0.6V
0.6V
0.6V
80% of VIN
3.7V
3.7V
3.7V
3.7V
3.7V
3.7V
3.7V
3.7V
Resolution
Externally Adjustable with 0.6V Internal Reference
100mV
100mV
100mV
100mV
100mV
100mV
100mV
100mV
Block Diagram
AAT2608
VINBUCK
Buck1
ENBUCK
VCC
A
LX
Control
P
2.2µH
10µF
PGND
2.2µF
FBBUCK
Bias, Control, and OTP
A
LDO 1
LDO1
Output
Voltage Trim
ENLD2
LDO 2
2.2µF
A
ENLD3
A
LDO 3
A
LDO 4
2.2µF
A
ENLD5
A
ENLD6
2.2µF
A
ENLD7
A
ENLD8
LDO5
LDO 6
1µF
A
LDO6
Output
Voltage Trim
LDO 7
A
LDO 8
1µF
LDO7
Output
Voltage Trim
VIN8
2.2µF
1µF
A
Output
Voltage Trim
VIN7
1µF
LDO4
LDO 5
VIN6
2.2µF
A
Output
Voltage Trim
VIN5
1µF
LDO3
Output
Voltage Trim
ENLD4
1µF
LDO2
Output
Voltage Trim
VIN34
P
AGND
Output
Voltage Trim
ENLD1
P
1µF
A
LDO8
A
1µF
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202206A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 25, 2012
5
DATA SHEET
AAT2608
Single 800mA Switching Converter and Eight-Channel 300mA LDO Regulator
Typical Characteristics−Step-Down (Buck) Converter
Input Current vs. Input Voltage
Efficiency vs. Output Current
(Buck VOUT = 1.2V; Switching; All LDOs Disabled)
(Buck VOUT = 1.2V)
100
90
90
80
80
Efficiency (%)
Input Current (µA)
100
70
60
50
60
50
40
VIN = 2.7V
VIN = 3.6V
VIN = 4.2V
VIN = 5.5V
30
20
40
30
70
10
2.7
3.1
3.5
3.9
4.3
4.7
5.1
0
0.1
5.5
1
10
Input Voltage (V)
1.5
1.00
1.0
0.50
0.00
-0.50
VIN = 2.7V
VIN = 3.6V
VIN = 4.2V
VIN = 5.5V
-1.00
10
100
1000
Line Regulation (%)
Load Regulation (%)
(Buck VOUT = 1.2V)
1.50
1
IOUT = 1mA
IOUT = 10mA
IOUT = 200mA
IOUT = 400mA
IOUT = 800mA
0.5
0.0
-0.5
-1.0
-1.5
2.7
Output Current (mA)
3.9
4.3
4.7
5.1
5.5
3.5
1.25
3.0
1.20
2.5
1.15
2.0
1.10
1.5
1.05
1.0
1.00
0.5
0.95
0.0
0.90
-0.5
(Buck VOUT = 1.2V; VIN = 3.6V; IOUT = 100mA)
5
0.7
4
0.6
3
0.5
2
0.4
1
0.3
0
0.2
-1
0.1
-2
0.0
-3
-0.1
Time (100µs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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Input Current
(bottom) (100mA/div)
1.30
Output Current
(500mA/div) (bottom)
Output Voltage
(50mV/div) (top)
3.5
Soft Start
Enable Voltage (top) (1V/div)
Output Voltage (middle) (1V/div)
Load Transient
6
3.1
Input Voltage (V)
(Buck VOUT = 1.2V; VIN = 3.6V; IOUT = 80mA to 800mA)
Time (100µs/div)
1000
Line Regulation
Load Regulation
(Buck VOUT = 1.2V; COUT = 22µF)
-1.50
0.1
100
Output Current (mA)
DATA SHEET
AAT2608
Single 800mA Switching Converter and Eight-Channel 300mA LDO Regulator
Typical Characteristics−LDO1-LDO8
Input Current vs. Input Voltage
Load Regulation
(LDO1 VOUT = 1.85V)
40
0.5
38
0.4
Load Regulation (%)
Input Current (µA)
(Contributed By Each LDO)
36
34
32
30
28
26
24
22
20
2.7
3.1
3.5
3.9
4.3
4.7
5.1
0.3
0.2
0.1
0.0
-0.1
-0.2
-0.3
-0.4
-0.5
0.1
5.5
Input Voltage (V)
VIN = 2.7V
VIN = 3.6V
VIN = 4.2V
VIN = 5.5V
1
(VOUT = 3V)
0.5
VIN = 3.3V
VIN = 3.6V
VIN = 4.2V
VIN = 5.5V
0.4
0.3
0.2
0.1
0.0
-0.1
-0.2
-0.3
-0.4
10
100
0.3
0.2
0.1
0.0
-0.1
-0.2
-0.3
-0.4
-0.5
2.7
1000
Output Current (mA)
IOUT = 1mA
IOUT = 100mA
IOUT = 150mA
IOUT = 300mA
0.4
Line Regulation (%)
Load Regulation (%)
1000
(LDO1 VOUT = 1.85V)
0.5
1
100
Line Regulation
Load Regulation
-0.5
0.1
10
Output Current (mA)
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Line Regulation
(VOUT = 3V)
0.5
IOUT = 1mA
IOUT = 100mA
IOUT = 150mA
IOUT = 300mA
Line Regulation (%)
0.4
0.3
0.2
0.1
0.0
-0.1
-0.2
-0.3
-0.4
-0.5
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT2608
Single 800mA Switching Converter and Eight-Channel 300mA LDO Regulator
Typical Characteristics−LDO1-LDO8 (continued)
Output Voltage Error vs. Temperature
Output Voltage Error vs. Temperature
(LDO1 VOUT = 1.85V; VIN = 3.6V)
IOUT = 1mA
IOUT = 250mA
0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
-50
-25
0
25
50
75
1.0
Output Voltage Error (%)
Output Voltage Error (%)
1.0
(LDO VOUT = 3V)
IOUT = 1mA
IOUT = 250mA
0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
-50
100
-25
Temperature (°C)
Load Transient
75
100
(VIN(DC) = 5V; VOUT = 1.85V; IOUT = 100mA)
1.4
80
1.95
1.2
70
1.90
1.0
1.85
0.8
1.80
0.6
1.75
0.4
1.70
0.2
1.65
0.0
1.60
-0.2
60
PSRR (dB)
Output Voltage
(50mV/div) (top)
50
Power Supply Rejection Ratio (PSRR)
2.00
Output Current
(200mA/div) (bottom)
8
25
Temperature (°C)
(LDO VOUT = 1.85V; VIN = 3.6V; IOUT = 30mA to 300mA)
Time (200µs/div)
0
50
40
30
20
10
0
10
100
1000
10000
100000
Frequency (Hz)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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1000000
DATA SHEET
AAT2608
Single 800mA Switching Converter and Eight-Channel 300mA LDO Regulator
Functional Block Diagram
ENBUCK
VCC
VCC
VCC
Bias
ENLD1
Bias
UVLO
VCC
LDO1
VINBUCK
+
A
P
OTP
LX
N
PGND
A
Control Logic
P
VCC
Compensation
ENLD8
1.5 MHz
Oscillator
Bias
FBBUCK
Feedback
VIN8
Error
Amp
Sawtooth
Generator
+
A
Soft Start
Thermal
Shutdown
LDO8
PWM
Comparator
+
A
OTP
A
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202206A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 25, 2012
9
DATA SHEET
AAT2608
Single 800mA Switching Converter and Eight-Channel 300mA LDO Regulator
Functional Description
The AAT2608 is a highly integrated voltage regulating
power management unit for mobile handsets or other
portable devices. It includes an 800mA switch-mode
step-down converter and eight low-noise, high-PSRR
low-dropout (LDO) regulators. It operates from an input
voltage between 2.7V and 5.5V making it ideal for lithium-ion or 5V regulated power sources. All nine converters have separate enable pins for ease of use.
Synchronous StepDown (Buck) Converter
The AAT2608 switch-mode step-down converter is a
constant frequency peak current mode PWM converter
with internal compensation. The input voltage range is
2.7V to 5.5V. The output voltage range is 0.6V to 80%
of VINBUCK. The high 1.5MHz switching frequency allows
the use of small external inductor and capacitor.
The step-down converter offers soft-start to limit the
current surge seen at the input and eliminate output
voltage overshoot. The current across the internal
P-channel power switch is sensed and turns off when the
current exceeds the current limit. Also, thermal protection completely disables switching if internal dissipation
becomes excessive, thus protecting the device from
damage. The junction over-temperature threshold is
145°C with 25°C of hysteresis.
The Buck converter is designed for a peak continuous
output current of 800mA. It was designed to maintain
over 80% efficiency at its maximum rated output current load of 800mA with a 1.2V output. Peak efficiency
is above 90%. It also has excellent transient response,
load regulation, and line regulation.
LDO Regulators
The AAT2608 includes eight LDO regulators. The regulators operate from the 2.7V to 5.5V input voltage to a
regulated output voltage. Each LDO regulator has its
own independent enable pin. All LDOs have a fixed output programmed during manufacturing. Each LDO consumes 30µA of quiescent current and is stable with a
small 1.0μF ceramic output capacitor. These LDOs offer
high power supply rejection and provide over-current
and over-temperature protection.
10
Application Information
Synchronous StepDown (Buck) Converter
The step-down converter uses peak current mode control with slope compensation to maintain stability for
duty cycles greater than 50%. The output inductor value
must be selected so the inductor current down-slope
meets the internal slope compensation requirements.
Table 1 displays suggested inductor values for various
output voltages.
Manufacturer’s specifications list both the inductor DC
current rating, which is a thermal limitation, and the
peak current rating, which is determined by the saturation characteristics. The inductor should not show any
appreciable saturation under normal load conditions.
Some inductors may meet the peak and average current
ratings yet result in excessive losses due to a high DCR.
Always consider the losses associated with the DCR and
its effect on the total converter efficiency when selecting
an inductor.
Input Capacitor
Select a 4.7μF to 10μF X7R or X5R ceramic capacitor for
the input; see Table 3 for suggested capacitor components. To estimate the required input capacitor size,
determine the acceptable input ripple level (VPP) and solve
for CIN. The calculated value varies with input voltage and
is a maximum when VCC is double the output voltage.
CIN =
VO
V
· 1- O
VIN
VIN
VPP
- ESR · FS
IO
VO
V
· 1- O
VIN
VIN
CIN(MIN) =
=
1
for VIN = 2 · VO
4
1
VPP
- ESR · 4 · FS
IO
Always examine the ceramic capacitor DC voltage coefficient characteristics when selecting the proper value.
For example, the capacitance of a 10μF, 6.3V, X5R
ceramic capacitor with 5.0V DC applied is actually about
6μF.
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DATA SHEET
AAT2608
Single 800mA Switching Converter and Eight-Channel 300mA LDO Regulator
The maximum input capacitor RMS current is:
VO
V
· 1- O
VIN
VIN
IRMS = IO ·
The input capacitor RMS ripple current varies with the
input and output voltage and will always be less than or
equal to half of the total DC load current.
VO
V
· 1- O
VIN
VIN
=
D · (1 - D) =
For VIN = 2 * VO
IRMS =
VO
· 1-
0.52 =
1
2
IO
2
VO
VIN
The term VIN
appears in both the input voltage
ripple and input capacitor RMS current equations and is
a maximum when VO is twice VCC. This is why the input
voltage ripple and the input capacitor RMS current ripple
are a maximum at 50% duty cycle.
The input capacitor provides a low impedance loop for
the edges of pulsed current drawn by the AAT2608 stepdown switching converter. Low ESR/ESL X7R and X5R
ceramic capacitors are ideal for this function. To minimize stray inductance, the capacitor should be placed as
closely as possible to the IC. This keeps the high frequency content of the input current localized, minimizing
EMI and input voltage ripple.
A laboratory test set-up typically consists of two long
wires running from the bench power supply to the evaluation board input voltage pins. The inductance of these
wires, along with the low-ESR ceramic input capacitor,
can create a high-Q network that may affect converter
performance. This problem often becomes apparent in
the form of excessive ringing in the output voltage during load transients. Errors in the loop phase and gain
measurements can also result.
Since the inductance of a short PCB trace feeding the
input voltage is significantly lower than the power leads
from the bench power supply, most applications do not
exhibit this problem.
In applications where the input power source lead inductance cannot be reduced to a level that does not affect
the converter performance, a high ESR tantalum or aluminum electrolytic should be placed in parallel with the
low ESR, ESL bypass ceramic. This dampens the high Q
network and stabilizes the system.
Output Capacitor
The output capacitor limits the output ripple and provides holdup during large load transitions. A 10μF to
22μF X5R or X7R ceramic capacitor typically provides
sufficient bulk capacitance to stabilize the output during
large load transitions and has the ESR and ESL characteristics necessary for low output ripple; see Table 2 for
suggested capacitor components
The output voltage droop due to a load transient is
dominated by the capacitance of the ceramic output
capacitor. During a step increase in load current, the
ceramic output capacitor alone supplies the load current
until the loop responds. Within several switching cycles,
the loop responds and the inductor current increases to
match the load current demand. The relationship of the
output voltage droop during the several switching cycles
to the output capacitance can be estimated by:
COUT =
3 · ∆ILOAD
VDROOP · FS
Once the average inductor current increases to the DC
load level, the output voltage recovers. The above equation establishes a limit on the minimum value for the
output capacitor with respect to load transients.
The internal voltage loop compensation also limits the
minimum output capacitor value to 10μF. This is due to
its effect on the loop crossover frequency (bandwidth),
phase margin, and gain margin. Increased output capacitance will reduce the crossover frequency with greater
phase margin.
The maximum output capacitor RMS ripple current is
given by:
IRMS(MAX) =
1
VOUT · (VIN(MAX) - VOUT)
L · FS · VIN(MAX)
2· 3
·
Dissipation due to the RMS current in the ceramic output
capacitor ESR is typically minimal, resulting in less than
a few degrees rise in hot-spot temperature.
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11
DATA SHEET
AAT2608
Single 800mA Switching Converter and Eight-Channel 300mA LDO Regulator
LDO Regulators
Input Capacitor
Typically, a 1.0μF or larger ceramic capacitor is recommended for CVCC, CVINBUCK, CVIN34, CVIN5, CVIN6, CVIN7, and
CVIN8 in most applications. The input capacitor should be
located as close to the inputs of the device as practically
possible. CVCC, CVINBUCK, CVIN34, CVIN5, CVIN6, CVIN7, and CVIN8
values greater than 1.0μF will offer superior input line
transient response and will assist in maximizing power
supply ripple rejection.
Output Capacitor
For proper load voltage regulation and operational stability, a capacitor is required between the LDOx and
AGND pins. The COUTx capacitor connection to the LDO
regulator ground pin should be made as direct as practically possible for maximum device performance.
The AAT2608's LDO regulators have been specifically
designed to function with very low ESR ceramic capacitors. Although the device is intended to operate with
these low ESR capacitors, it is stable over a very wide
range of capacitor ESR, thus it will also work with higher
ESR tantalum or aluminum electrolytic capacitors.
However, for best performance, ceramic capacitors are
recommended.
Typical output capacitor values for maximum output current conditions range from 1μF to 10μF.
Thermal Calculations
There are three types of losses associated with the
AAT2608 total power management solution (one stepdown converter and eight LDO regulators): switching
losses, conduction losses, and quiescent current losses.
Conduction losses are associated with the RDS(ON) characteristics of the internal power switches/FETs of the stepdown converter and the power loss associated with the
voltage difference across the pass switch/FET of the
eight LDO regulators. Switching losses are dominated by
the gate charge of the power output switching devices.
At full load, assuming continuous conduction mode
(CCM), a simplified form of the losses is given by the
following (quiescent and switching losses are ignored,
since conduction losses are so dominant):
12
PB =
IOB2 · (RDS(ON)H · VOB + RDS(ON)L · [VINBUCK - VOB])
VIN
PLDO1 = ILDO1 · (VCC - VOL1)
PLDO2 = ILDO2 · (VCC - VOL2)
PLDO3 = ILDO3 · (VIN34 - VOL3)
PLDO4 = ILDO4 · (VIN34 - VOL4)
PLDO5 = ILDO5 · (VIN5 - VOL5)
PLDO6 = ILDO6 · (VIN6 - VOL6)
PLDO7 = ILDO7 · (VIN7 - VOL7)
PLDO8 = ILDO8 · (VIN8 - VOL8)
PTOTAL = PB + PLDO1 + PLDO2 + PLDO3 + PLDO4 + PLDO5 + PLDO6 + PLDO7 + PLDO8
PB: Power dissipation of the DC-DC regulator
IOB: Output current of the specific DC-DC regulator
RDS(ON)H: Resistance of the internal high-side switch/FET
RDS(ON)L: Resistance of the internal low-side switch/FET
VOB: Output voltage of the DC-DC regulator
VCC: Input voltage of the DC-DC regulator, LDO1, and
LDO2
PLDOx: Power dissipation of the specific LDO regulator
ILDOx: Output current of the specific LDO regulator
VINBUCK: Input voltage of the step-down converter.
VIN34: Input voltage of LDO3 and LDO4
VIN5: Input voltage of LDO5
VIN6: Input voltage of LDO6
VIN7: Input voltage of LDO7
VIN8: Input voltage of LDO8
VOLx: Output voltage of the specific LDO regulator
PTOTAL: Total power dissipation of the AAT2608
Since RDS(ON) and conduction losses all vary with input
voltage, the dominant losses should be investigated over
the complete input voltage range. Given the total conduction losses, the maximum junction temperature
(125°C) can be derived from the θJA for the TQFN44-28
package which is 50°C/W.
TJ(MAX) = PTOTAL · θJA + TA
TJ(MAX) = PTOTAL · θJA + TA
TJ(MAX): Maximum junction temperature
PTOTAL: Total conduction losses
ΘJA: Thermal impedance of the package
TA: Ambient temperature
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DATA SHEET
AAT2608
Single 800mA Switching Converter and Eight-Channel 300mA LDO Regulator
Layout
The suggested PCB layout for the AAT2608 is shown in
Figures 2 and 3. The following guidelines should be used
to help ensure a proper layout.
1. The input capacitors (C1, C2, C3, C4, C5, C6) should
connect as closely as possible to VINBUCK (Pin 22),
VIN34 (Pin 5), VIN5 (Pin 18), VIN6 (Pin 17), VIN7
(Pin 16) VIN8 (Pin 15), VCC (Pin 6), and AGND/
PGND (Pins 4 and 24).
2. C13 (the step-down converter output capacitor) and
L1 should be connected as closely as possible. The
connection of L1 to the LX pin should be as short as
possible.
Manufacturer
TDK
Part Number/
Type
Inductance
(μH)
Rated Current
(A)
DCR (mΩ)
(max)
1.2
1.8
2.2
3.3
1
1.8
2.7
3.3
1.2
1.8
2.2
2.7
3.3
1
1.5
2.2
3.3
4.3
3.6
3.2
2.5
2.6
2.35
2.03
1.8
2.8
2.45
2.35
1.95
1.8
4
3.7
3.2
2.9
25
32
40
60
30
50
60
65
20
25
28
30
35
19 (typ)
22 (typ)
29 (typ)
36 (typ)
LTF5022
WE-TPC Type M
Wurth Electronik
WE-TPC Type MH
Murata
3. The feedback trace or FBBUCK pin (Pin 28) should
be separated from any power trace and connected
as closely as possible to the load point. Sensing
along a high current load trace will degrade DC load
regulation. If external feedback resistors are used,
they should be placed as closely as possible to the
FBBUCK pin (Pin 28) to minimize the length of the
high impedance feedback trace.
4. The resistance of the trace from the load return to
the PGND (Pin 24) should be kept to a minimum.
This will help to minimize any error in DC regulation
due to differences in the potential of the internal
signal ground and the power ground.
5. For good thermal coupling, PCB vias are required
from the pad for the TQFN44-28 exposed paddle to
the ground plane.
LQH55D
Size (mm)
LxWxH
5x5.2x2.2
4.8x4.8x1.8
4.8x4.8x2.8
5x5.7x4.7
Table 1: Suggested Inductor Components.
Manufacturer
AVX
TDK
Murata
Taiyo Yuden
Part Number
Value
Voltage
0603ZD105K
0603ZD225K
C1608X5R1E105K
C1608X5R1C225K
C1608X5R1A475K
C2012X5R1A106K
C3216X5R1A226K
GRM188R61C105K
GRM188R61A225K
GRM219R61A106K
GRM31CR71A226K
LMK107BJ475KA
1μF
2.2μF
1μF
2.2μF
4.7μF
10μF
22μF
1μF
2.2μF
10μF
22μF
4.7μF
10
10
25
16
10
10
10
16
10
10
10
10
Temp. Co.
Case
X5R
0603
0603
X5R
0805
1206
X5R
X7R
X5R
0603
0805
1206
0603
Table 2: Suggested Capacitor Components.
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13
DATA SHEET
AAT2608
Single 800mA Switching Converter and Eight-Channel 300mA LDO Regulator
VCC
TP5
C7
2.2µF
VCC
JP1
VINBUCK
TP1
C1
10µF
VINBUCK
TB1
Enable
L1
2.2µH
VINBUCK
U1
TP2
VIN34
C2
2.2µF
TP3
VIN5
C3
2.2µF
27
TP4
ENBUCK
22
VINBUCK
VIN6
C4
2.2µF
TP7
5
VIN8
TP6
VIN7
18
C5
2.2µF
C6
2.2µF
VCC
1
16
SW1
6
VCC
R2
1M
R3
1M
R4
1M
R5
1M
R6
1M
R7
1M
23
FBBUCK
28
R12
VIN5
LDO1
7
17
VIN6
VIN7
LDO2
8
16
15
VIN8
LDO3
9
AAT 2608
TP15
TP14
3
ENLD1
LDO4
10
2
ENLD2
LDO5
11
ENLD3
26
ENLD4
25
ENLD5
21
ENLD6
20
ENLD7
19
ENLD8
LDO6
LDO7
AGND PGND
24
R1
1M
LX
4
R8
1M
LDO8
C17
1µF
R11
AAT2608_TQFN44-28
VIN34
1
TP16
VOUT_BUCK
C16
10µF
TP12
TP11
TP10
12
LDO6
TP9
13
14
TP8
LDO8
LDO7
LDO5
LDO4
TP13
LDO2
LDO3
C14
1µF
LDO1
C15
1µF
C13
1µF
C12
1µF
C11
1µF
C10
1µF
C9
1µF
C8
1µF
Figure 1: AAT2608 Evaluation Board Schematic.
14
Figure 2: AAT2608 Evaluation Board
Top Side PCB Layout. Figure 3: AAT2608 Evaluation Board Bottom Side PCB Layout.
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DATA SHEET
AAT2608
Single 800mA Switching Converter and Eight-Channel 300mA LDO Regulator
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
TQFN44-28
9QXYY
AAT2608INJ-1-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
TQFN44-28
Pin 1 Dot
by Marking
2.600 ± 0.050
4.000 ± 0.050
Detail "A"
C0.3
4.000 ± 0.050
2.600 ± 0.050
Top View
Bottom View
0.400 ± 0.050
0.430 ± 0.050
0.750 ± 0.050
Side View
0.230 ± 0.050
0.203 REF
0.050 ± 0.050
Pin 1 Indicator
Detail "A"
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.
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15
DATA SHEET
AAT2608
Single 800mA Switching Converter and Eight-Channel 300mA LDO Regulator
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, 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
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16
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