AMS3108 - Advanced Monolithic Systems

AMS3108
Micropower 700mA Low Noise Fast Transient Response LDO
General Description
Features
The AMS3108 is a high performance linear regulator
with very low dropout voltage and excellent transient
response. It is designed to operate with wide input
voltage range of 1.5 – 12Volts making it ideal for two
step conversion while maintaining high efficiency for
many power sensitive applications. The device is
capable of supplying 700mA of output current with a
typical dropout voltage of 550mV. The product is
available in either fixed or adjustable output voltage.
The linear regulator has been optimized for noise
sensitive applications.
The device includes an
Enable pin for electrical on/off of the regulator.
Forcing the Enable pin to logic low shuts down the
LDO and reduces the supply current below 1µA. In
addition, the AMS3108 provides an open collector
Power Good (PG) signal to allow supply monitoring
and sequencing of other supplies.
The product includes complete short-circuit and
thermal protection. The combination of these two
internal protection circuits gives the device a
comprehensive safety system to safe guard against
extreme adverse operating conditions.
The AMS3108 is available in a thermally enhanced
SOIC-8 EDP package, and it is rated for -40°C to
+125°C temperature range.
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VIN range: 1.5 – 12V
Fixed and Adjustable output voltage as low
as 0.6V
700mA maximum output current
550mV of typical dropout voltage at 700mA
Low self noise
Enable (EN) pin for LDO on/off
Power Good (PG) output
120µA typical supply current
ByPass pin (CBYP) for low PSRR and output
noise
PSRR > 40dB at 10KHz
Stable with Electrolytic, Tantalum or
Ceramic capacitors
Current Limit protection
Over-Temperature Shutdown
-40 to +125°C temperature range
Thermally enhanced SOIC-8 exposed
paddle package
RoHS & WEEE compliant
Applications
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ASIC Power Supplies In:
¾ Set-top Boxes, Desktops, Notebooks
¾ Graphic Cards, Printers and Copiers
DVD, Blue-Ray DVD writers
LCD TVs and LCD monitors
Infotainment
Wireless & RF: applications
DSP and FPGA Power Supplies
Medical Instrumentation
SMPS Post-Regulator
Typical Application
02/11/2010
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AMS3108
Micropower 700mA Low Noise Fast Transient Response LDO
Pin Description (SOIC-8 EDP package)
Pin #
Symbol
1
BYP
Reference Bypass pin. Connect an external capacitor from CBYP to ground to
bypass the noise generated by the internal bandgap. This improves power supply
rejection ratio and output noise.
2
GND
Ground
3
GND
Ground
4
VIN
5
VOUT
Output Voltage
ADJ
Provides feedback to error amplifier from the resistive divider that sets the output
voltage.
NC
No Connection
7
PG
Power Good pin. It is an open collector, active high output that indicates the status
of the output voltage. When output voltage (VOUT) exceeds the PG trip threshold,
the PG pin goes in to a high impedance state. When the device is out of regulation
or shutdown, the PG pin is pulled low. A 10KΩ to 1MΩ resistor should be
connected from PG to VOUT.
8
EN
Enable pin. It controls the electrical on/off of the device. When connected to logic
low, the device shuts off and consumes less than 1µA of current. Logic high will
resume normal operation.
9
GND
6
Description
Input supply Voltage. It powers the internal control circuitry and the internal power
switch. Bypass VIN with at ceramic capacitor from this pin to ground.
Expose pad. Connected to PCB ground plane for good thermal dissipation.
Pin Configuration
SOIC-8 EDP (Top View)
BYP 1
GND 2
GND 3
VIN
02/11/2010
4
8 EN
9
GND
7 PG
6 ADJ / NC
5 VOUT
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AMS3108
Micropower 700mA Low Noise Fast Transient Response LDO
Absolute Maximum Ratings (1)
Recommended Operating Conditions (2)
Maximum Input Supply Voltage (VIN)………....……..… -0.3V to 15V
Enable Voltage (EN)……………..…..………….……… -0.3V to 15V
Power Good (PG).……………..…..………………….… -0.3V to 15V
Adjustable Voltage (ADJ)……………………………….… -0.3V to 3V
ByPass Voltage (BYP)…………..…..…………………… -0.3V to 3V
Storage Temperature Range……………................. -65⁰C to 150⁰C
Lead Temperature…………………..………….…………..…… 260⁰C
Junction Temperature………...………………..……..………… 125⁰C
Input Voltage………………………………….……..…….. 1.5V to 12V
Ambient Operating Temperature…………….……… -40⁰C to 125⁰C
Thermal Information
8L SOIC EP θJA
(3)
………………………………………..…...45⁰C/W
Electrical Characteristics
Unless otherwise noted: VIN=3.3V, VOUT=1.8V; CIN=10 µF, COUT=22µF, -40⁰C≤TA=TJ≤85⁰C, TJ(Max.)=125°C; Typical values are TA=25°C
Parameter
Symbol
Conditions
Output Voltage Accuracy
VOUT
Adjustable Voltage
VADJ
Adjustable VOUT only
IADJ_Bias
IOUT_Max
Adjustable VOUT only
Adjustable bias current
Maximum Output Current
Load Regulation
Line Regulation
Supply Current
Shutdown Current
Current Limit
Dropout Voltage
ISUP
ISHDN
ILIM
Output Noise Voltage
Typ.
Max.
Units
3
%
0.6
0.606
V
10
100
nA
mA
-3
0.594
700
IOUT= 0 – 700mA
0.6
VIN=3.0 – 12V; IOUT=100mA
0.15
VIN=3.3V, Io=0A
VIN=3.3V, VEN=0V
120
<1
800
IOUT=100mA; VOUT=95% of VOUT(NOM)
220
IOUT=250mA; VOUT=95% of VOUT(NOM)
300
IOUT=500mA; VOUT=95% of VOUT(NOM)
425
IOUT=750mA; VOUT=95% of VOUT(NOM)
600
F=10KHz Io=20mA
33
%
%
150
VDO
ΔVOUT/ΔVIN
PSRR
Min.
en
µA
µA
mA
mV
BW: 100Hz–100 KHz
COUT = 22µF
ILOAD = 150mA
No CBYP
118
CBYP = 10nF
33
dB
µV(rms)
Enable Threshold Low
Enable Threshold High
Input Enable Low Current
Input Enable High Current
Power Good Low Threshold
Power Good High Threshold
VEN(L)
VEN(H)
IEN(L)
IEN(H)
VPG
VPG
VEN = 0V
VEN = 1.5V
% of VOUT PG ON
% of VOUT PG OFF
Power Good Output Low Voltage
VPGL
IPG_SINK = 500μA,Fault Condition
200
PG off, VPG = 12V
0.01
μA
145
15
°C
°C
Power Good Leakage Current
IPG
Thermal Shutdown
Thermal Shutdown Hysteresis
TSD
TSD_HYS
Notes:
1.
2.
3.
1
1.1
0
150
97
V
V
nA
nA
%
%
300
mV
10
300
89
Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device.
Measured on approximately 1” square of 1 oz. copper.
The total power dissipation for SO-8 EDP package is recommended to 2.5W rated at 25⁰C ambient temperature. The thermal resistance Junction to Case
is 45⁰C/W. Total power dissipation for the switching regulator and the LDO should be taken in consideration when calculating the output current capability
of each regulator.
02/11/2010
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A
AMS3
3108
Micrropower 70
00mA Low
w Noise Fas
st Transien
nt Respons
se LDO
Outputt Voltage Tem
mperature Va
ariation
(Fixe
ed Voltage Option)
O
VO = 1.8V
1.825
Adjustable (ADJ
J) Voltage Te
emperature
Variation (Adju
ustable Voltage Option)
0.606
Output Voltage (V)
Adjust Voltage (V)
Ty
ypical Perfo
ormance Characteris
C
stics (TA = 25°C
2
unless otherwise
o
sp
pecified)
0.604
0.602
1.815
1.805
1.795
0.600
-25
-50
0
25
50
7
75
-50
100 12
25
-25
Ambient Temperature
e (ºC)
‐
‐50°C
20
25°C
15
10
5
100°C
0
100
0
200
30
00
400
50
00
600
30
20
25°C
10
0
0
70
00
1
Output Voltage Change (%)
Output Voltage Error (%)
0.1
0.0
-0.1
-0.2
3
4
5
6
7
8
9 10 11 12
12
2
Load Re
egulation
0.2
0
-0.2
-0.4
-0.6
0.0
Input Voltage (V)
02/11/2010
0
2
oltage (V)
Input Vo
0.2
9
100 125
125°C
40
Line Regulation VO = 1.8V, IO = 100mA
6
75
50
Outpu
ut Current (A
A)
3
50
Shutd
down Current vs. Input Voltage
IGND vs
s. Output Currrent VO=1.8V
V, Vin=2.5V
25
25
5
Ambient Te
emperature (ºC)
(
Shutdown Current (µA)
Ground Current (mA)
30
0
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dvanced-mono
olithic.com
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0.1
0
Output Current
C
(A)
1.0
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A
AMS3
3108
Micrropower 70
00mA Low
w Noise Fas
st Transien
nt Respons
se LDO
Ty
ypical Perfo
ormance Characteris
C
stics (TA = 25°C
2
unless otherwise
o
sp
pecified)
Dropout
p
Voltage
g (mV)
(
)
600
500
400
100°C
25°C
300
‐50°C
200
100
VOUT = 1.8V
Dropout Voltage (mV)
VDO vs. Ou
utput Curren
nt
700
VDO vs. Tempera
ature (IO = 70
00mA)
7
700
6
600
5
500
4
400
3
300
2
200
0
0
10
00
200 30
00 400 50
00 600
Outpu
ut Current (m
mA)
700
0
25
50
75
-25
Ambient Tem
mperature (°C)
100
Enable Starrt-Up
Load Transient
50mA to 550mA
A, VOUT=1.8V, VIN=3.3V CIN= COUT=4.7µF
02/11/2010
0
-50
IOUT = 0 to 350mA, VOUT = 1.8V, VIN = 3.0V, CIN=C
= OUT=10µF
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olithic.com
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AMS3108
Micropower 700mA Low Noise Fast Transient Response LDO
Functional Block Diagram
VOUT
VIN
Over Current
Protection
R1
*Note*
-
ADJ
Error
Amp
EN
+
R2
Power Good
Comparator
Over Temperature
Protection
PG
-
BYP
+
VREF= 0.6V
*Note*: Resistors R1 and R2
are integrated into the part
for the Fixed-Voltage option.
GND
Figure 1: Block Diagram of AMS 3108
02/11/2010
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AMS3108
Micropower 700mA Low Noise Fast Transient Response LDO
Device Summary
The AMS3108 is a high voltage low drop out linear
regulator with a current capability of up to 700mA. The
LDO has an input voltage range of 1.5V to 12V with
an output voltage as low as 0.6V and is stable with a
wide range of ceramic, tantalum, and electrolytic
output capacitors.
Shutdown/Enable
The Enable (on/off) input threshold voltage is 1.1V.
When disabled the LDO quiescent current decreases
to a typical value of <1µA.
Fault Protection
Short circuit and over-temperature shutdown disable
the converter and LDO in the event of an overload
condition. Overtemp shutdown disables the device
when the junction temperature exceeds 145 ºC. The
output current is internally limited to 800mA.
Input Capacitor
An input bypass capacitor ranging from 1µF to 10µF
is required. The capacitor should be placed as close
as possible to the device and not be placed more than
1 inch from the LDO.
Output Capacitor
The output capacitor requirements range from the
minimum value required to guarantee stability to
larger values required to meet the extreme transient
response requirements. Values range from 10 to
22µF X5R ceramic capacitors. Due to the extreme
voltage coefficient of X5R ceramic capacitors, the
voltage rating should be at least double the maximum
applied voltage.
Bypass Capacitor
If the ByPass (BYP) is available, connecting a
capacitor between the BYP pin and ground can
significantly reduce output noise. Values can range
from 0pF to 10nF, depending on the sensitivity to
output noise in the application. The start-up speed of
the AMS3108 is inversely proportional to the size of
the bypass capacitor. Applications requiring a slow
ramp-up of output voltage should consider larger
values of bypass capacitance. Likewise, if rapid turnon is necessary, consider omitting CBYP.
02/11/2010
Because the ByPass (BYP) pin is high-impedance,
careful considering must be taken in the PCB layout
to minimize noise pickup, and capacitors must be
selected to minimize current leakage.
Current
leakage into the BYP pin will directly affect the
regulator’s accuracy and should be kept low as
possible. Using high quality ceramic and film type’s
capacitors are recommended for their low leakage
characteristics.
Adjustable Version: Feedback Resistor Selection
Choosing AMS 3108 with adjustable output voltage
option allows the user to select an output voltage by
using an external resistor divider. AMS 3108 uses a
0.6V reference voltage at the positive terminal of the
error amplifier. To set the output voltage a
programming resistor from the adjust pin (ADJ) to
ground must be selected (See Pg.1). A 10kΩ resistor
is a good selection for a programming resistor R2. A
higher value may result in an excessively sensitive
feedback node while a lower value will draw more
current and degrade the light load efficiency. The
equation for selecting the voltage specific resistor is:
R1 =
Vout
Vref
-1 ·R2 =
1.8V
0.6V
-1 ·10kΩ = 20kΩ
Table 1: Adjustable Feedback Resistor values
R1 (kΩ)
VOUT (V)
(R2=10kΩ)
1.8
20.0
2.5
31.6
3.3
45.3
5.0
73.2
Power Good
During operation, fault conditions can occur
unexpectedly. Such conditions include input voltage
dropout (low VIN), overheating, or overloading
(excessive output current). If any of these conditions
occurs, the PG pin will set an “error flag”. The PG pin,
which is an open-collector output, will go LOW when
VOUT is less than 95% or the specified output voltage.
When the voltage at VOUT is greater than 95% of the
specified output voltage, the PG pin is HIGH. A logic
pull-up resistor of 10KΩ is recommended at this
output. The pin can be left disconnected if unused.
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AMS3108
Micropower 700mA Low Noise Fast Transient Response LDO
PCB Layout
The following guidelines should be followed to insure
proper layout.
1. VIN Capacitor. A low ESR ceramic bypass
capacitor must be placed as close to the IC as
possible.
2. Adjustable (ADJ) Feedback Resistors. The
adjustable feedback resistors should be placed as
close as possible the IC. Minimize the length of
the trace from the feedback pin to the resistors.
This is a high impedance node susceptible to
interference from external RF noise sources.
3. Ground.
4. For good thermal performance vias are required
to couple the exposed tab of the SO-8 package to
the PCB ground plane. The via diameter should
be 0.3mm to 0.33mm positioned on a 1.2mm grid.
02/11/2010
Output Power and Thermal Limits
The AMS3108 junction temperature and current
capability depends on the internal dissipation and the
junction to case thermal resistance of the SO-8
exposed paddle package.
Additionally, the paddle and PCB temperature will be
elevated due to the total losses of the LDO and of
other circuits mounted to the PCB.
Tjmax = Pd·θjc + Tpcb + Tamb
The internal losses contribute to the junction
temperature rise above the paddle and PCB
temperature.
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AMS3108
Micropower 700mA Low Noise Fast Transient Response LDO
Figure 2: AMS3108 Evaluation Board
Top Side
Figure 3: AMS3108 Evaluation Board
Bottom Side
2
1
U1
1
C4
10nF
2
3
4
Vin
Enable
BYP
8
EN
PG
7
GND
PG
GND
ADJ/NC
VIN
VOUT
R3
100k
6
R1
5
AMS3108
Vout
C1
10uF
C2
22uF
C3
n/a
R2
10.0k
gnd
gnd
Figure 4: AMS3108 Evaluation Board Schematic
Component
C1
C2
C3
C4
1.2V
1.8V
2.5V
3.3V
5.0V
R1
R2
R3
U1
02/11/2010
Table 2: AMS3108 Evaluation Board Bill of Materials
Value
Manufacturer Manufacturer Part Number
10µF, 50V, X5R, 1210, Ceramic
22µF, 10V, X5R, 0805, Ceramic
Optional Feedforward
10nF, 50V,20%,X7R,0603
10.0kΩ, 0.1W, 0603 1%
20.0kΩ, 0.1W, 0603 1%
31.6kΩ, 0.1W, 0603 1%
45.3kΩ, 0.1W, 0603 1%
73.2kΩ, 0.1W, 0603 1%
10.0kΩ, 0.1W, 0603 1%
100kΩ, 0.1W, 0603 1%
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Taiyo Yuden
Taiyo Yuden
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Murata
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Various
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GRM188R71H103MA01
CRCW0603xxKxFKEA
CRCW0603xxKxFKEA
CRCW0603xxKxFKEA
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CRCW060310K0FKEA
CRCW0603100KFKEA
AMS3108 SOIC-8 EDP
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AMS3108
Micropower 700mA Low Noise Fast Transient Response LDO
Ordering Information
Device
AMS3108S(1)(2)
Package
SOIC-8 EDP
AMS3108S-XX(1)(2)(3)
SOIC-8 EDP
Notes:
1. Available in tape and reel only. A reel contains 2,500 devices.
2. Available in lead-free package only. Device is fully WEEE and RoHS compliant
3. Need to specify output voltage option ( )
Outline Drawing and Landing Pattern
SOIC-8 package dimensions are inches (millimeters) unless otherwise noted.
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