LTC3499EMS8#TR [Linear]
LTC3499 - 750mA Synchronous Step-Up DC/DC Converters with Reverse-Battery Protection; Package: MSOP; Pins: 8; Temperature Range: -40°C to 85°C;
| 型号： | LTC3499EMS8#TR |
| 厂家： | 
Linear |
| 描述： | LTC3499 - 750mA Synchronous Step-Up DC/DC Converters with Reverse-Battery Protection; Package: MSOP; Pins: 8; Temperature Range: -40°C to 85°C 电池 开关 光电二极管 |
| 文件： | 总16页 (文件大小：216K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC3499/LTC3499B
750mA Synchronous
Step-Up DC/DC Converters
with Reverse-Battery Protection
FEATURES
DESCRIPTION
TheLTC®3499/LTC3499Baresynchronous,fixedfrequency
step-up DC/DC power converters with integrated reverse
battery protection that protect and disconnect the devices
and load when the battery polarity is reversed while
delivering high efficiency in a small (3mm × 3mm) DFN
package. Trueoutputdisconnecteliminatesinrushcurrent
and allows zero load current in shutdown.
n
Reverse-Battery Protection for DC/DC Converter
and Load
n
High Efficiency: Up to 94%
n
Generates 5V at 175mA from a 1.8V Input
n
Operates from 1.8V to 5.5V Input Supply
n
2V to 6V Adjustable Output Voltage
n
Inrush Current Controlled During Start-Up
n
Output Disconnnect in Shutdown
The devices feature an input voltage range of 1.8V to 5.5V
enablingoperationfromtwoalkalineorNiMHbatteries.The
switching frequency is internally set at 1.2MHz allowing
the use of tiny surface mount inductors and capacitors.
A minimal number of external components are required
to generate output voltages ranging from 2V to 6V. The
LTC3499 features automatic Burst Mode operation to
increase efficiency at light loads, while the LTC3499B
features continuous switching at light loads.
n
Low Noise 1.2MHz PWM Operation
n
Tiny External Components
Automatic Burst Mode® Operation (LTC3499)
n
n
Continuous Switching at Light Loads (LTC3499B)
n
Overvoltage Protection
n
8-Lead (3mm × 3mm × 0.75mm) DFN
and MSOP Packages
APPLICATIONS
The soft-start time is externally programmable through a
small capacitor. Anti-ring circuitry reduces EMI emissions
by damping the inductor in discontinuous mode. The
devices feature <1μA shutdown supply current, integrated
overvoltage protection and are available in both 8-pin
(3mm × 3mm) DFN and 8-pin MSOP packages.
n
Medical Equipment
n
Digital Cameras
n
MP3 Players
Handheld Instruments
n
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Two AA Cells to 5V Synchronous Boost Converter
Battery Current vs VIN
4.7μH
1.0
V
IN
1.8V TO 3.2V
SHDN = 0V
OUT
V
= 0V
+
V
SW
OUT
FB
2.2μF
IN
0.5
0
LTC3499
V
OUT
V
5V
ON OFF
SHDN
VC
175mA
1M
10μF
100k
330pF
SS
GND
324k
–0.5
–1.0
0.01μF
3499 TA01
–6
–4
–2
0
2
4
6
V
AND SW VOLTAGE (V)
IN
3499 TA01b
3499fb
1
LTC3499/LTC3499B
(Note 1)
ABSOLUTE MAXIMUM RATINGS
V to GND..................................................... – 7V to 7V
FB, SS to GND............................................. – 0.3V to 7V
Operating Temperature Range
IN
V
to GND .............................................. – 0.3V to 7V
OUT
SW to V
SW to GND
................................................... – 7V to 1V
(Notes 3, 4)......................................... –40°C to 85°C
Storage Temperature Range.................. –65°C to 125°C
Lead Temperature (Soldering, 10 sec)
OUT
DC............................................................... –7V to 7V
Pulsed < 100ns........................................... –7V to 8V
SHDN to GND................................................. – 7V to 7V
MSOP .............................................................. 300°C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
SHDN
1
2
3
4
8
7
6
5
VC
FB
SHDN
1
2
3
4
8
7
6 V
VC
FB
OUT
V
IN
9
V
SW
IN
SW
V
OUT
GND
5
SS
GND
SS
MS8 PACKAGE
8-LEAD PLASTIC MSOP
DD PACKAGE
8-LEAD PLASTIC DFN
T
= 125°C, θ = 160°C/W
JA
JMAX
T
= 125°C, θ = 45°C
JA
JMAX
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3499EDD#PBF
LTC3499BEDD#PBF
LTC3499EMS8#PBF
LTC3499BEMS8#PBF
TAPE AND REEL
PART MARKING
LBRB
PACKAGE DESCRIPTION
8-Lead Plastic DFN
TEMPERATURE RANGE
–40°C to 85°C
LTC3499EDD#TRPBF
LTC3499BEDD#TRPBF
LTC3499EMS8#TRPBF
LTC3499BEMS8#TRPBF
LCDZ
8-Lead Plastic DFN
–40°C to 85°C
LTBRC
8-Lead Plastic MSOP
8-Lead Plastic MSOP
–40°C to 85°C
LTCFB
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS The l denotes specifications that apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. VIN = 2.4V, VOUT = 5V, SHDN = 2.4V, TA = TJ unless otherwise noted.
SYMBOL
Supply
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
l
l
V
V
V
Minimum Start-Up Voltage
Output Voltage Adjust Range
FB Voltage
1.6
1.8
6
V
V
IN
2
OUT
FB
1.195
1.220
1.245
V
3499fb
2
LTC3499/LTC3499B
ELECTRICAL CHARACTERISTICS The l denotes specifications that apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. VIN = 2.4V, VOUT = 5V, SHDN = 2.4V, TA = TJ unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
= 1.22V
MIN
TYP
3
MAX
50
UNITS
nA
I
I
I
I
FB Input Current
V
FB
FB
l
V
V
Quiescent Current
No Output Load
SHDN = 0V, V
300
0.1
600
1
μA
VIN
IN
IN
Quiescent Current in Shutdown
= 0V
OUT
μA
SD
Quiescent Current – Burst Mode Operation
V
V
Current at 2.4V (LTC3499 Only)
OUT
20
1.5
μA
μA
BURST
IN
Current at 5V (LTC3499 Only)
I
I
NMOS Switch Leakage
PMOS Switch Leakage
NMOS Switch On Resistance
V
V
= 6V
0.1
0.1
5
5
μA
μA
NMOS
SW
= 6V, V = 0V
PMOS
OUT
SW
R
V
OUT
V
OUT
= 3.3V
= 5V
0.45
0.4
Ω
Ω
NMOS
PMOS
R
PMOS Switch On Resistance
V
OUT
V
OUT
= 3.3V
= 5V
0.58
0.45
Ω
Ω
l
I
t
NMOS Current Limit
0.75
80
1
1
A
ns
LIM
DLY, ILIM
Current Limit Delay to Output
Maximum Duty Cycle
Note 2
60
85
l
l
l
D
D
%
MAX
MIN
Minimum Duty Cycle
0
%
f
Frequency Accuracy
1.2
40
–5
5
1.4
MHz
μmhos
μA
OSC
G
Error Amplifier Transconductance
Error Amplifier Source Current
Error Amplifier Sink Current
SS Current Source
mEA
SOURCE
SINK
I
I
I
μA
V
SS
= 1V
–3
6.8
400
μA
SS
V
V
V
V
Overvoltage Threshold
Overvoltage Hysteresis
V
OV
OUT
OUT
mV
OV(HYST)
Shutdown
l
l
V
SHDN Input Low
SHDN Input High
SHDN Input Current
0.2
1
V
V
SHDN(LOW)
SHDN(HIGH)
V
Measured at SW
1.2
I
SD
μA
Reverse Battery
l
l
l
I
I
I
V
V
Reverse-Battery Current
V
OUT
V
OUT
V
OUT
= 0V, V = V
= V = –6V
5
μA
μA
μA
VOUT,REVBATT
VIN,REVBATT
SHDN,REVBATT
OUT
IN
SHDN
SHDN
SHDN
SW
and V Reverse-Battery Current
= 0V, V = V
= V = –6V
–5
–5
IN
SW
IN
SW
SHDN Reverse-Battery Current
= 0V, V = V
= V = –6V
SW
IN
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 4: These ICs include overtemperature protection that is intended
to protect the devices during momentary overload conditions. Junction
temperatures will exceed 125°C when overtemperature protection is
active. Continuous operation above the specified maximum operating
temperature range may impair device reliability.
Note 2: Specification is guaranteed by design and not 100% tested in
production.
Note 3:The LTC3499E/LTC3499BE are guaranteed to meet device
specifications from 0°C to 85°C. Specifications over the –40°C to 85°C
operating temperature are assured by design, characterization and
correlation with statistical process controls.
3499fb
3
LTC3499/LTC3499B
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
2-Cell to 5V Efficiency
vs Load Current (LTC3499 Only)
Li-Ion to 5V Efficiency
vs Load Current (LTC3499 Only)
2-Cell to 5V Efficiency
vs Load Current (LTC3499B Only)
100
90
80
70
60
50
40
30
20
10
0
100
90
100000
10000
100
90
100000
10000
1000
100
EFFICIENCY
EFFICIENCY
80
80
70
1000
100
70
60
50
40
30
POWER LOSS
POWER LOSS
60
50
40
10
1
10
V
V
V
= 3.2V
= 2.4V
= 1.8V
V
V
V
= 4.2V
= 3.6V
= 3V
V
V
V
= 3.2V
= 2.4V
= 1.8V
IN
IN
IN
IN
IN
IN
1
IN
IN
IN
0.1
0.1
0.1
1
10
100
1000
0.1
1
10
100
1000
1
10
LOAD CURRENT (mA)
1000
0.1
100
LOAD CURRENT (mA)
LOAD CURRENT (mA)
3499 G17
3499 G01
3499 G03
Burst Mode Output Current
Threshold vs Input Voltage
(LTC3499 Only)
Current Limit Accuracy
vs Temperature
2-Cell to 3.3V Efficiency
vs Load Current (LTC3499 Only)
1.04
1.03
1.02
60
50
40
30
20
10
0
100
90
100000
V
= 5V
OUT
10000
EFFICIENCY
80
70
1000
100
1.01
1.00
0.99
0.98
0.97
0.96
60
50
40
10
1
POWER LOSS
V
V
V
= 3V
= 2.4V
= 1.8V
IN
IN
IN
0.1
–25
0
50
1.8
2.8
3.3
3.8
4.3
4.8
–50
75
100
25
2.3
0.1
1
10
100
1000
INPUT VOLTAGE (V)
TEMPERATURE (°C)
LOAD CURRENT (mA)
3499 G04
3499 G05
3499 G02
Maximum Output Current
Capability vs VIN
No Load Input Current vs VIN
(LTC3499 Only)
Burst Mode Quiescent Current
vs Temperature (LTC3499 Only)
200
180
160
140
120
100
80
30
25
20
15
10
5
800
700
600
500
400
300
200
100
0
V
> V
OUT
IN
V
> V
OUT
IN
V
= 3.3V
OUT
V
= 3.3V
OUT
V
= 5V
OUT
V
= 5V
OUT
60
40
20
0
0
1.5
2.5
3.5
(V)
4.5
5.5
–50
0
25
50
75
100
3.5
(V)
–25
1.5
2.5
4.5
5.5
V
TEMPERATURE (°C)
V
IN
IN
3499 G07
3499 G08
3499 G06
3499fb
4
LTC3499/LTC3499B
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
Oscillator Frequency
vs Temperature
VIN and SW Reverse-Battery
FB Voltage vs Temperature
Current vs VIN and SW Voltage
1.0
0.5
30
25
20
15
10
5
1.2225
1.2220
1.2215
1.2210
1.2205
1.2200
1.2195
1.2190
1.2185
SHDN = 0V
V
= 0V
OUT
0
–0.5
–1.0
0
–25
0
50
–50
75
100
25
–50
0
25
50
75
100
–25
–6
–4
–2
0
2
4
6
TEMPERATURE (°C)
V
AND SW VOLTAGE (V)
TEMPERATURE (°C)
IN
3499 G09
3499 G08
3499 G11
Burst Mode Operation
(LTC3499 Only)
Fixed Frequency Discontinous
Mode Operation
Load Transient 50mA to 200mA
SW
2V/DIV
V
OUT
V
OUT
200mV/DIV
50mV/DIV
200mA
50mA
I
I
LOAD
L
I
100mA/DIV
100mA/DIV
L
50mA/DIV
3499 G12
3499 G13
3499 G14
V
V
= 2.4V
= 5V
20μs/DIV
V
V
= 2.4V
= 5V
200μs/DIV
V
V
= 2.4V
= 5V
OUT
200ns/DIV
IN
OUT
L = 4.7μH
IN
OUT
IN
I
= 50mA to 200mA
L = 4.7μH
LOAD
R
C
C
V
= 10μF
= 100k
OUT
Z
= 10pF (FEEDFORWARD CAPACITOR FROM
TO FB)
C = 680pF
FF
OUT
F
OUT
L = 4.7μH
C
= 10μF
Soft-Start into 25Ω Load
Fixed Frequency Operation
V
IN
2V/DIV
SS
2V/DIV
SW
2V/DIV
V
OUT
I
L
2V/DIV
100mA/DIV
I
L
200mA/DIV
3499 G16
3499G15
V
V
= 2.4V
= 5V
200ns/DIV
V
V
= 2.4V
= 5V
1ms/DIV
IN
OUT
L = 4.7μH
IN
OUT
L = 4.7μH
C
C
= 0.01μF
SS
= 10μF
OUT
3499fb
5
LTC3499/LTC3499B
PIN FUNCTIONS
SHDN(Pin1):ShutdownInputforIC. Connecttoavoltage
greater than 1.2V to enable and a voltage less than 0.2V
to disable the LTC3499/LTC3499B.
V
(Pin 6): Power Supply Output. Connect a low ESR
OUT
output filter capacitor from this pin to the ground plane.
FB (Pin 7): FB Input to Error Amplifier. Connect a resistor
divider tap from V
The output voltage can be adjusted between 2V and 6V.
Referring to the Functional Block Diagram, the output
voltage is given by:
V
(Pin 2): Input Supply Voltage. The valid operating
to this pin to set the output voltage.
IN
OUT
voltage is between 1.8V to 5.5V. V has reverse battery
IN
protection. Since the LTC3499/LTC3499B use V as the
IN
main bias source, bypass with a low ESR ceramic capaci-
tor of at least 2.2μF.
⎡
⎤
⎥
⎦
⎛
⎞
R1
R2
VOUT =1.22• 1+
SW (Pin 3): Switch Pin. Connect an inductor from V to
⎢
⎜
⎝
⎟
⎠
IN
⎣
this pin with a value between 2.2μH and 10μH. Keep PCB
trace lengths as short and wide as possible to minimize
EMI and voltage overshoot. If the inductor current falls to
zero or SHDN is low an internal 250Ω antiringing switch
VC (Pin 8): Error Amplifier Output. A frequency com-
pensation network is connected from this pin to GND to
compensate the boost converter loop. See Closing the
Feedthrough Loop section for guidelines.
is connected from V to SW to minimize EMI.
IN
GND (Pin 4): Signal and Power Ground for the IC.
ExposedPad—DDOnly(Pin9):Ground.Mustbesoldered
to the PCB power ground plane for electrical connection
and rated thermal performance.
SS (Pin 5): Soft-Start Input. Connect a capacitor from
SS to ground to control the inrush current at start-up. An
internal 3μA current source charges this pin. SS will be
dischargedifSHDNispulledlow,thermalshutdownoccurs
or V is below the minimum operating voltage.
IN
3499fb
6
LTC3499/LTC3499B
FUNCTIONAL BLOCK DIAGRAM
C
IN
+
V
IN
1.8V TO 5.5V
L
2
3
V
IN
SW
REVERSE-BATTERY COMPARATOR
ANTI-RING
2507
+
1 = CLOSED
1 = CLOSED
0.7V
–
–
–
+
+
V
SELECT
OV COMPARATOR
V
OUT
6
7
V
OUT
+
–
1 = OFF
ERROR AMPLIFIER
C
FF
(OPTIONAL)
1.22V
+
–
R1
R2
6.8V
ENABLE
FB
PWM
C
OUT
THERMAL SD
SLEEP
LOGIC
AND
DRIVERS
VC
I
ZERO
8
5
C
C1
C
C2
RZ
1.2MHz
OSCILLATOR
SLOPE
COMPENSATION
3
3MA
SS
5k
+
–
C
SS
PWM COMPARATOR
ENABLE
TSD
Burst Mode
CONTROL
(LTC3499 ONLY)
+
–
SLEEP
CURRENT LIMIT COMPARATOR
REFERENCE
1A
TYP
–
SHDN
1
BIAS
ENABLE
UVLO
+
0.8V
SD
GND
4
3499 F01
Figure 1: Functional Block Diagram
3499fb
7
LTC3499/LTC3499B
OPERATION
TheLTC3499/LTC3499Bprovidehighefficiency, lownoise
powerforboostapplicationswithoutputvoltagesupto6V.
OperationcanbebestunderstoodbyreferringtotheFunc-
tional Block Diagram in Figure 1. The synchronous boost
converters are housed in either an 8-lead (3mm × 3mm)
DFN or MSOP package and operates at a fixed 1.2MHz.
In the event of a commanded shutdown or thermal shut-
down (TSD), C is discharged through a nominal 5kΩ
SS
impedance to GND. Once the condition is removed and SS
is discharged near ground, a soft-start will automatically
be re-initiated.
Error Amplifier
With a 1.6V typical minimum V voltage these devices
IN
are well suited for applications using two or three alkaline
or nickel-metal hydride (NiMH) cells or one Lithium-Ion
(Li+)cell.TheLTC3499/LTC3499Bhaveintegratedcircuitry
whichprotectsthebattery,IC,andcircuitrypoweredbythe
device in the event that the input batteries are connected
backwards (reverse battery protection). The true output
disconnect feature eliminates inrush current and allows
A transconductance amplifier generates an error voltage
from the difference between the positive input internally
connected to the 1.22V reference and the negative input
connectedtoFB.Asimplecompensationnetworkisplaced
fromVCtoground. Internalclampslimittheminimumand
maximumerroramplifieroutputvoltageforimprovedlarge
signal transient response. A voltage divider from V
to
OUT
V
to be zero volts during shutdown. The current mode
OUT
GND programs the output voltage via FB from 2V to 6V
and is defined by the following equation:
architecture simplifies loop compensation with excellent
load transient response. The low R , low gate charge
DS(ON)
⎡
⎤
⎥
⎦
⎛
⎞
R1
R2
synchronous switches eliminate the need for an external
Schottkydioderectifier,andprovideefficienthighfrequency
pulse width modulation (PWM). Burst Mode quiescent
VOUT =1.22• 1+
⎢
⎜
⎝
⎟
⎠
⎣
current to the LTC3499 is only 20μA from V , maximiz-
IN
Current Sensing
ing battery life. The LTC3499B does not have Burst Mode
operation and the device continues switching at constant
frequency. This results in the absence of low frequency
output ripple at the expense of light load efficiency.
Lossless current sensing converts the peak current signal
into a voltage which is summed with the internal slope
compensation. This summed signal is compared to the
error amplifier output to provide a peak current control
command for the PWM. Peak switch current is limited
to 750mA minimum.
LOW NOISE FIXED FREQUENCY OPERATION
Shutdown
Antiringing Control
The LTC3499/LTC3499B are shut down by pulling SHDN
below 0.2V, and activated by pulling the pin above 1.2V.
The antiringing control connects a resistor across the
inductor to damp the ringing on SW in discontinuous
conduction mode. The LC resonant ringing (L = inductor,
SHDN can be driven above V or V
as long as it is
IN
OUT
limited to less than the absolute maximum rating.
C
= capacitance on SW) is low energy, but can cause
SW
EMI radiation if antiringing control is not present.
Soft-Start
Thesoft-starttimeisprogrammedwithanexternalcapaci-
tor to ground on SS. An internal current source charges
Zero Current Comparator
Thezerocurrentcomparatormonitorstheinductorcurrent
to the output and shuts off the synchronous rectifier once
this current reduces to approximately 40mA, preventing
negative inductor current.
the capacitor, C , with a nominal 3μA. The voltage on SS
SS
is used to clamp the voltage on VC. The soft-start time
is given by
t
= C (μF) • 200
SS
(msec)
3499fb
8
LTC3499/LTC3499B
OPERATION
Reverse-Battery Protection
re-enter sleep if the output load remains less than the
sleep threshold. The frequency of this intermittent PWM
(or burst) operation is proportional to load current.
Therefore, as the load current drops further below the
burst threshold, the LTC3499 operates in PWM mode
less frequently. When the load current increases above
the burst threshold, the LC3499 will resume continuous
PWM operation seamlessly.
Pluggingthebatteryinbackwardsposesasevereproblem
to most power converters. At a minimum the battery
will be quickly discharged. Almost all ICs have an inher-
ent diode from V (cathode) to ground (anode) which
IN
conducts appreciable current when V drops more than
IN
0.7V below ground. Under this condition the integrated
circuit will most likely be damaged due to the excessive
currentdraw.Thereexiststhepossibilityforthebatteryand
circuitry powered by the device to also be damaged. The
LTC3499/LTC3499Bhaveintegratedcircuitrywhichallows
negligible current flow under a reverse-battery condition,
protecting the battery, device and circuitry attached to the
output. A graph of the reverse-battery current drawn is
shown in the Typical Performance Characteristics.
Referring to the Functional Block Diagram, an optional
capacitor,C ,betweenV andFBinsomecircumstances
FF
OUT
can reduce peak-to-peak V
ripple and input quiescent
OUT
current during Burst Mode operation. Typical values for
C range from 10pF to 220pF.
FF
Output Disconnect and Inrush Current Limiting
The LTC3499/LTC3499B are designed to allow true output
disconnect by eliminating body diode conduction of the
Discrete methods of reverse battery protection put ad-
ditional dissipative elements in the high current path
reducing efficiency while increasing component count
to implement protection. The LTC3499/LTC3499B do not
suffer from either of these drawbacks.
internal P-channel MOSFET transistor. This allows V
OUT
to go to zero volts during shutdown without drawing any
current from the input source. It also provides for inrush
current limiting at turn-on, minimizing surge current seen
by the input supply.
Burst Mode Operation (LTC3499 only)
Portable devices frequently spend extended time in low
power or stand-by mode, only drawing high power when
specificfunctionsareenabled. Inordertoimprovebattery
life in these types of products, high power converter ef-
ficiency needs to be maintained over a wide output power
range. In addition to its high efficiency at moderate and
heavy loads, the LTC3499 includes automatic Burst Mode
operation that improves efficiency of the power converter
at light loads. Burst Mode operation is initiated if the
output load current falls below an internally programmed
threshold (see Typical Performance graph, Output Load
V > V
Operation
IN
OUT
The LTC3499/LTC3499B will maintain voltage regulation
when the input voltage is above the output voltage. This is
achievedbyterminatingtheswitchingonthesynchronous
P-channelMOSFETandapplyingV staticallyonthegate.
IN
This will ensure the volts • seconds of the inductor will
reverse during the time current is flowing to the output.
Since this mode will dissipate more power in the IC, the
maximum output current is limited in order to maintain
an acceptable junction temperature:
Burst Mode Threshold vs V ). Once initiated the Burst
IN
125– TA
Mode operation circuitry shuts down most of the circuitry
in the LTC3499, only keeping alive the circuitry required
to monitor the output voltage.
IOUT(MAX)
≅
θJA • V +1.5 – V
(
)
(
)
IN
OUT
where T = ambient temperature and θ is the package
A
JA
This state is referred to as sleep. In sleep, the LTC3499
only draws 20μA from the input supply, greatly enhancing
efficiency. When the output has drooped approximately
1% from its nominal regulation point, the LTC3499
wakes up and commences normal PWM operation. The
output capacitor will recharge causing the LTC3499 to
thermal resistance (45°C/W for the DD8 and 160°C/W
for the MS8).
For example at V = 4.5V, V
DD8 package, the maximum output current is 330mA.
= 3.3V and T = 85°C in the
A
IN
OUT
3499fb
9
LTC3499/LTC3499B
APPLICATIONS INFORMATION
PCB LAYOUT GUIDELINES
The inductor current ripple is typically set to 20% to 40%
of the maximum inductor current. For high efficiency,
choose an inductor with high frequency core material,
such as ferrite, to reduce core losses. The inductor should
have low ESR (equivalent series resistance) to reduce the
The high speed operation of the LTC3499/LTC3499B
demand careful attention to board layout. Advertised per-
formancewillnotbeachievedwithcarelesslayout.Figure 2
shows the recommended component placement. A large
copper area will help to lower the chip temperature. Traces
2
I R power losses, and must be able to handle the peak
inductor current without saturating. To minimize radiated
noise, use a toroidal or shielded inductor. See Table 1 for
some suggested inductor suppliers.
carrying high current (SW, V , GND) are kept short.
OUT
The lead length to the battery should be kept as short as
possible. The V and V
ceramic capacitors should be
IN
OUT
placed as close to the IC pins as possible.
Table 1. Inductor Vendor Information
PART NUMBER
SUPPLIER
WEB SITE
C
C2
EXPOSED PAD FOR DD8
MSS5131 and
Coilcraft
www.coilcraft.com
MOS6020 Series
C
C1
RZ
R2
VC
SLF7028 and
SLF7045 Series
TDK
www.component.tdk.com
1
2
3
4
8
7
6
5
SHDN
LQH55D Series
Murata
Sumida
Toko
www.murata.com
www.sumida.com
www.tokoam.com
V
IN
FB
V
CDRH4D28 Series
9
R1
C
C
IN
L
+
D53LC and
D62CB Series
V
BATT
OUT
SW
DT0703 Series
CoEV
FDK
www.coev.net
www.fdk.com
SS
MJPF2520 Series
OUT
GND
C
SS
Output Capacitor Selection
3499 F02
The output voltage ripple has three components to it. The
bulk value of the capacitor is set to reduce the ripple due
to charge into the capacitor each cycle. The maximum
ripple voltage due to charge is given by:
Figure 2: Recommended Component Placement
COMPONENT SELECTION
Inductor Selection
VIN
VRBULK =IP •
C
OUT • VOUT • f
(
)
The LTC3499/LTC3499B allow the use of small surface
mountinductorsandchipinductorsduetothefast1.2MHz
switching frequency. A minimum inductance value of
2.2μH is required. Larger values of inductance will allow
greater output current capability by reducing the inductor
ripple current. Increasing the inductance above 10μH
will increase total solution area while providing minimal
improvement in output current capability.
where I = peak inductor current and f = switching
P
frequency.
The ESR (equivalent series resistance) is usually the most
dominant factor for ripple in most power converters. The
ripple due to capacitor ESR is simply given by:
V
= I • C
P ESR
RCESR
where C
= capacitor equivalent series resistance.
ESR
3499fb
10
LTC3499/LTC3499B
APPLICATIONS INFORMATION
TheESL(equivalentseriesinductance)isalsoanimportant
factor for high frequency converters. Using small surface
mount ceramic capacitors, placed as close as possible to
into a copper plane with as much area as possible. If the
junction temperature continues to rise, the part will go
into thermal shutdown where switching will stop until the
temperature drops.
V
, will minimize ESL.
OUT
Low ESR capacitors should be used to minimize output
voltageripple.A4.7μFto10μFoutputcapacitorissufficient
for most applications and should be placed as close to
Closing the Feedback Loop
The LTC3499/LTC3499B utilize current mode control,
with internal slope compensation. Current mode control
eliminates the 2nd order filter due to the inductor and
outputcapacitorexhibitedinvoltagemodecontrollers,thus
simplifying it to a single pole filter response. The product
of the modulator control to output DC gain and the error
amp open loop gain gives the DC gain of the system:
V
as possible. Larger values may be used to obtain
OUT
even lower output ripple and improve transient response.
X5R and X7R dielectric materials are preferred for their
ability to maintain capacitance over wide voltage and
temperature ranges.
Input Capacitor Selection
VREF
GDC =GCONTROL •GEA
•
The input filter capacitor reduces peak currents drawn
from the input source and reduces input switching noise.
Ceramiccapacitorsareagoodchoiceforinputdecoupling
duetotheirlowESRandabilitytowithstandreversevoltage
(i.e. non-polar nature). The capacitor should be located
as close as possible to the device. In most applications a
2.2μF input capacitor is sufficient. Larger values may be
used without limitations. Table 2 shows a list of several
ceramic capacitor manufacturers.
VOUT •GCURRENT _SENSE
VIN
IOUT
GCONTROL = 2•
,
1
GEA ~1000, GCURRENT _SENSE
=
RDS ON
(
)
The output filter pole is given by:
IOUT
π • VOUT •COUT
Table 2. Capacitor Vendor Information
fFILTER_POLE
=
SUPPLIER
AVX
WEB SITE
(
)
www.avxcorp.com
www.murata.com
www.component.tdk.com
www.t-yuden.com
Murata
TDK
where C
is the output filter capacitor.
OUT
The output filter zero is given by:
Taiyo Yuden
1
fFILTER_ZERO
=
Thermal Considerations
2•π •RESR •COUT
(
)
For the LTC3499/LTC3499B to deliver full output power, it
is imperative that a good thermal path be provided to dis-
sipate the heat generated within the package. For the DFN
package, this can be accomplished by taking advantage
of the large thermal pad on the underside of the device.
It is recommended that multiple vias in the printed circuit
board be used to conduct heat away from the part and
where R
is the capacitor equivalent series resistance.
ESR
A troublesome feature of the boost regulator topology is
the right half plane (RHP) zero, given by:
2
VIN
fRPHZ
=
2•π •IOUT • VOUT •L
(
)
3499fb
11
LTC3499/LTC3499B
APPLICATIONS INFORMATION
V
There is a resultant gain increase with a phase lag which
makes it difficult to compensate the loop. At heavy loads
the right half plane zero can occur at a relatively low
frequency. The loop gain is typically rolled off before the
RHP zero frequency.
OUT
6
ERROR AMPLIFIER
R1
R2
1.22V
+
–
FB
7
The typical error amp compensation is shown in Figure 3,
following the equations for the loop dynamics:
VC
8
1
fPOLE1
~
R
Z
C
C2
2•π •10e6•C
(
)
C1
C
C1
3499 F03
which is extremely close to DC.
1
Figure 3: Typical Error Amplifier Compensation
fZERO1
=
=
2•π •R •C
(
)
Z
C1
1
fPOLE2
2•π •R •C
(
)
Z
C2
3499fb
12
LTC3499/LTC3499B
TYPICAL APPLICATIONS
Lithium-Ion to 5V, 350mA
Lithium-Ion to 5V Efficiency
100
90
100000
L
4.7μH
10000
V
IN
C
EFFICIENCY
+
IN
Li-Ion
2.2μF
V
IN
SW
OUT
FB
80
3.1V TO 4.2V
1000
s5R
LTC3499
70
60
50
40
30
V
OUT
V
POWER LOSS
100
5V
ON OFF
SHDN
VC
350mA
1M
C
OUT
10
10μF
100k
s5R
SS
GND
V
V
V
= 4.2V
= 3.6V
= 3V
324k
IN
IN
IN
1
330pF
0.01μF
0.1
C
C
: TAIYO YUDEN X5R JMK212BJ225MD
IN
OUT
1
10
LOAD CURRENT (mA)
1000
0.1
100
: TAIYO YUDEN X5R JMK212BJ106MD
3499 F04a
L: COILCRAFT MSS5131-472MLB
3499 G03
Two Cells to 5V, 175mA
Two Cells to 5V Efficiency
100
90
100000
10000
L
4.7μH
V
IN
C
+
IN
EFFICIENCY
2 AA CELLS
2.2μF
V
IN
SW
OUT
FB
80
70
1000
100
1.8V TO 3.2V
s5R
LTC3499
V
OUT
V
5V
ON OFF
SHDN
VC
175mA
POWER LOSS
1M
C
60
50
40
10
1
OUT
10μF
100k
s5R
SS
V
V
V
= 3.2V
= 2.4V
= 1.8V
IN
IN
IN
GND
324k
330pF
0.01μF
0.1
0.1
1
10
100
1000
C
C
: TAIYO YUDEN X5R JMK212BJ225MD
IN
OUT
: TAIYO YUDEN X5R JMK212BJ106MD
LOAD CURRENT (mA)
3499 F05a
L: COILCRAFT MSS5131-472MLB
3499 G01
3499fb
13
LTC3499/LTC3499B
PACKAGE DESCRIPTION
DD Package
8-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1698)
0.675 p 0.05
3.5 p 0.05
2.15 p 0.05 (2 SIDES)
1.65 p 0.05
PACKAGE
OUTLINE
0.25 p 0.05
0.50
BSC
2.38 p 0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
R = 0.115
0.38 p 0.10
TYP
5
8
3.00 p 0.10
(4 SIDES)
1.65 p 0.10
(2 SIDES)
PIN 1
TOP MARK
(NOTE 6)
(DD) DFN 1203
4
1
0.25 p 0.05
0.75 p 0.05
0.200 REF
0.50 BSC
2.38 p 0.10
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-1)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON TOP AND BOTTOM OF PACKAGE
3499fb
14
LTC3499/LTC3499B
PACKAGE DESCRIPTION
MS8 Package
8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660)
0.889 p 0.127
(.035 p .005)
5.23
(.206)
MIN
3.20 – 3.45
(.126 – .136)
3.00 p 0.102
(.118 p .004)
0.52
0.65
(.0256)
BSC
0.42 p 0.038
(.0165 p .0015)
TYP
(.0205)
REF
(NOTE 3)
8
7 6
5
RECOMMENDED SOLDER PAD LAYOUT
3.00 p 0.102
(.118 p .004)
(NOTE 4)
4.90 p 0.152
(.193 p .006)
DETAIL “A”
0.254
(.010)
0o – 6o TYP
GAUGE PLANE
1
2
3
4
0.53 p 0.152
(.021 p .006)
1.10
(.043)
MAX
0.86
(.034)
REF
DETAIL “A”
0.18
(.007)
SEATING
PLANE
0.22 – 0.38
0.1016 p 0.0508
(.009 – .015)
(.004 p .002)
0.65
(.0256)
BSC
TYP
MSOP (MS8) 0307 REV F
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
3499fb
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
LTC3499/LTC3499B
TYPICAL APPLICATION
Two Cells to 3.3V, 250mA
Two Cells to 5V Efficiency
100
90
100000
10000
L
4.7μH
EFFICIENCY
C
V
+
IN
IN
2.2μF
V
IN
2 AA CELLS
SW
OUT
FB
80
70
1000
100
s5R
1.8V TO 3.2V
LTC3499
V
OUT
V
3.3V
ON OFF
SHDN
VC
250mA
562k
332k
C
OUT
60
50
40
10
1
10μF
POWER LOSS
100k
s5R
SS
V
V
V
= 3V
= 2.4V
= 1.8V
GND
IN
IN
IN
330pF
0.01μF
0.1
0.1
1
10
100
1000
C
C
: TAIYO YUDEN X5R JMK212BJ225MD
IN
: TAIYO YUDEN X5R JMK212BJ106MD
LOAD CURRENT (mA)
OUT
3499 F06a
L: COILCRAFT MSS5131-472MB
3499 F06b
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1930/LT1930A
1A (I ), 1.2MHz/2.2MHz, High Efficiency Step-Up
High Efficiency, V : 2.6V to 16V, V
= 34V, I = 4.2mA/5.5mA,
OUT(MAX) Q
SW
IN
DC/DC Converter
I
< 1μA, ThinSOT Package
SD
LT1961
1.5A (I ), 1.25MHz, High Efficiency Step-Up
90% Efficiency, V : 3V to 25V, V
= 35V, I = 0.9mA,
OUT(MAX) Q
SW
IN
DC/DC Converter
I
< 6μA, MS8E Package
SD
LTC3400/LTC3400B
LTC3401
600mA (I ), 1.2MHz, Synchronous Step-Up
92% Efficiency, V : 0.5V to 5V, V
= 5V, I = 19μA/300μA,
SW
IN
OUT(MAX) Q
DC/DC Converter
I
< 1μA, ThinSOT Package
SD
1A (I ), 3MHz, Synchronous Step-Up DC/DC Converter
97% Efficiency, VIN: 0.5V to 5V, V
= 5.5V, I = 38μA,
Q
SW
OUT(MAX)
I
SD
< 1μA, 10-Lead MS Package
LTC3402
2A (I ), 3MHz, Synchronous Step-Up DC/DC Converter
97% Efficiency, VIN: 0.5V to 5V, V
< 1μA, 10-Lead MS Package
= 5.5V, I = 38μA,
Q
SW
OUT(MAX)
I
SD
LTC3421
3A (I ), 3MHz, Synchronous Step-Up DC/DC Converter
95% Efficiency, V : 0.5V to 4.5V, V
= 5.25V, I = 12μA,
Q
SW
IN
OUT(MAX)
OUT(MAX)
OUT(MAX)
with Output Disconnect
I
< 1μA, 24-Lead QFN Package
SD
LTC3422
1.5A (I ), 3MHz, Synchronous Step-Up DC/DC
95% Efficiency, V : 0.5V to 4.5V, V
= 5.25V, I = 25μA,
Q
SW
IN
Converter with Output Disconnect
I
< 1μA
SD
LTC3425
5A (I ), 8MHz, 4-Phase Synchronous Step-Up DC/DC
95% Efficiency, V : 0.5V to 4.5V, V
= 5.25V, I = 12μA,
Q
SW
IN
Converter with Output Disconnect
I
< 1μA, 32-Lead QFN Package
SD
LTC3427
500mA (I ), 1.25MHz, Synchronous Step-Up DC/DC
94% Efficiency, V : 1.8V to 5V, V
= 5.25V, I < 1μA,
OUT(MAX) SD
SW
IN
Converter with Soft-Start/Output Disconnect
DFN Package
LTC3429/LTC3429B
LTC3458/LTC3458L
LTC3525
600mA (I ), 550kHz, Synchronous Step-Up DC/DC
92% Efficiency, V : 0.5V to 4.3V, V
= 5V, I = 20μA,
SW
IN
OUT(MAX) Q
Converters with Soft-Start/Output Disconnect
I
< 1μA, ThinSOT Package
SD
1.4A/1.7A (I ), 1.5MHz, Synchronous Step-Up DC/DC
93% Efficiency, V : 1.5V to 6V, V
SD
= 7.5V/6V, I = 15μA,
SW
IN
OUT(MAX) Q
Converter with Soft-Start/Output Disconnect
I
< 1μA, DFN Package
400mA (I ), Synchronous Step-Up DC/DC
94% Efficiency, V : 0.5V to 4.5V, V
= 5.25V, I = 7μA,
SW
IN
OUT(MAX) Q
Converter in SC70
I
< 1μA, Output Disconnect
SD
3499fb
LT 1208 REV B• PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
16
●
●
© LINEAR TECHNOLOGY CORPORATION 2006
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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