1
LTC3202
3202fa
APPLICATIO S
U
FEATURES
DESCRIPTIO
U
TYPICAL APPLICATIO
U
s
White LED Backlighting
s
Programmable Boost Current Source
s
Low Noise Constant Frequency Operation
s
25% Less Input Current Than Doubler Charge Pump
s
High Output Current: Up To 125mA
s
Small Application Circuit
s
Regulated Output Voltage or Current
s
Automatic Soft-Start
s
V
IN
Range: 2.7V to 4.5V
s
No Inductors
s
1.5MHz Switching Frequency
s
I
CC
< 1
A in Shutdown
s
Available in 10-Pin MSOP and 3mm
3mm
DFN Packages
Low Noise, High Efficiency
Charge Pump for White LEDs
The LTC
3202 is a low noise, constant frequency charge
pump DC/DC converter that uses fractional conversion to
increase efficiency in white LED applications. The part can
be used to produce a regulated voltage or current of up to
125mA from a 2.7V to 4.5V input. Low external parts count
(two flying capacitors and two small bypass capacitors at
V
IN
and V
OUT
) make the LTC3202 ideally suited for small,
battery-powered applications.
An internal 2-bit DAC allows LED current to be adjusted for
LED brightness control. The LTC3202 also has thermal
shutdown protection and can survive a continuous short-
circuit from V
OUT
to GND. Built-in soft-start circuitry
prevents excessive inrush current during start-up. High
switching frequency enables the use of small external
capacitors. A low current shutdown feature disconnects
the load from V
IN
and reduces quiescent current to less
than1
A.
The LTC3202 is available in the 10-pin MSOP and 3mm
3mm DFN packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Programmable White LED Power Supply
3202 TA01
LTC3202
V
OUT
FB
GND
C4
1
F
C1
1
F
5, 11
3
2
C2
C2
+
C1
C1
+
CURRENT
PROGRAMMING
V
IN
3V TO 4.5V
10
4
1
36
36
36
36
36
36
C3
1
F
C2
1
F
D0
D1
V
IN
8
7
9
6
C1, C2, C3, C4 = MURATA GRM 39X5R105K6.3 OR TAIYO YUDEN JMK107BJ105MA
0mA TO 125mA
TOTAL CURRENT
V
IN
(AC COUPLED)
20mV/DIV
V
OUT
(AC COUPLED)
20mV/DIV
500ns/DIV
V
IN
= 3.6V
C
IN
= C
OUT
= 1
F
I
OUT
= 60mA
3202 G09
Input and Output Ripple
2
LTC3202
3202fa
V
IN
, V
OUT
to GND ......................................... 0.3V to 6V
D0, D1 ............................................. 0.3V to V
IN
+ 0.3V
V
OUT
Short-Circuit Duration ............................. Indefinite
I
OUT
(Note 2) ....................................................... 150mA
ORDER PART
NUMBER
MS PART MARKING
T
JMAX
= 150
C,
JA
= 120
C/W
LTWL
LTC3202EMS
ABSOLUTE AXI U
RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
(Note 1)
Consult LTC Marketing for parts specified with wider operating temperature ranges.
1
2
3
4
5
D1
FB
V
OUT
V
IN
GND
10
9
8
7
6
D0
C2
+
C1
+
C1
C2
TOP VIEW
MS PACKAGE
10-LEAD PLASTIC MSOP
Operating Temperature Range (Note 3) ...40
C to 85
C
Storage Temperature Range ..................65
C to 150
C
Lead Temperature (Soldering, 10 sec).................. 300
C
ORDER PART
NUMBER
DD PART MARKING
LABB
LTC3202EDD
TOP VIEW
11
DD PACKAGE
10-LEAD (3mm
3mm) PLASTIC DFN
10
9
6
7
8
4
5
3
2
1
D0
C2
+
C1
+
C1
C2
D1
FB
V
OUT
V
IN
SGND
T
JMAX
= 150
C,
JA
= 44
C/W,
JC
= 3
C/W
EXPOSED PAD IS PGND (PIN 11) MUST BE
CONNECTED TO GROUND PLANE
ELECTRICAL CHARACTERISTICS
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: Based on long-term current density limitations.
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C. V
IN
= 3.3V unless otherwise noted.
Note 3: The LTC3202E is guaranteed to meet performance specifications
from 0
C to 70
C. Specifications over the 40
C to 85
C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Input Power Supply
V
IN
Operating Voltage
q
2.7
4.5
V
I
CC
Operating Current
I
OUT
= 0mA, V
OUT
= 3.6V, V
IN
= D0 = D1 = 4.5V
q
2.5
5
mA
I
SHDN
Shutdown Current
V
OUT
= 0V
q
1
A
Feedback Pin Set Points
0.2V Setting Feedback Voltage
D0 = 1, D1 = 0, I
OUT
= 0mA, V
IN
= 3.6V
q
188
200
212
mV
0.4V Setting Feedback Voltage
D0 = 0, D1 = 1, I
OUT
= 0mA, V
IN
= 3.6V
q
380
400
420
mV
0.6V Setting Feedback Voltage
D0 = 1, D1 = 1, I
OUT
= 0mA, V
IN
= 3.6V
q
570
600
630
mV
I
FB
V
FB
= 0.8V
q
50
50
nA
Charge Pump
R
OL
Open Loop Output Impedance (1.5V
IN
V
OUT
)/I
OUT
V
IN
= 3.3V, V
OUT
= 4.4V, V
FB
= 0
q
4.5
6
V
OUT
Load Regulation (
V
OUT
/
I
OUT
)
I
OUT
= 10mA to 90mA,
V
FB
/
V
OUT
= 1
0.35
mV/mA
CLK Frequency
1.5
MHz
D0, D1
High Level Input Voltage (V
IH
)
q
1.3
V
Low Level Input Voltage (V
IL
)
q
0.4
V
Input Current (I
IH
)
DO, D1 = V
IN
q
1
1
A
Input Current (I
IL
)
DO, D1 = 0V
q
1
1
A
3
LTC3202
3202fa
V
FB
Set Point vs Input Supply
(200mV Setting)
V
FB
Set Point vs Input Supply
(400mV Setting)
V
FB
Set Point vs Input Supply
(600mV Setting)
V
FB
vs Load Current
Input Current vs Load Current
Oscillator Frequency vs Supply
Voltage
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
INPUT SUPPLY (V)
2.7
SET POINT (V)
0.21
0.20
0.19
3.0
3.3
3.6
3.9
3202 G01
4.2
4.5
I
LOAD
= 20
A
V
D0
= V
IN
V
D1
= 0V
T
A
= 85
C
T
A
= 40
C
T
A
= 25
C
INPUT SUPPLY (V)
2.7
SET POINT (V)
0.42
0.40
0.38
3.0
3.3
3.6
3.9
3202 G02
4.2
4.5
I
LOAD
= 40
A
V
D0
= 0V
V
D1
= V
IN
T
A
= 85
C
T
A
= 40
C
T
A
= 25
C
INPUT SUPPLY (V)
2.7
SET POINT (V)
0.63
0.60
0.57
3.0
3.3
3.6
3.9
3202 G03
4.2
4.5
I
LOAD
= 60
A
V
D0
= V
D1
= V
IN
T
A
= 25
C, 85
C
T
A
= 40
C
LOAD CURRENT (mA)
0
FEEDBACK VOLTAGE (V)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
25
50
75
100
125
150
3202 G04
V
D0
= V
D1
= V
IN
C
IN
= C
OUT
= C
FLY1
= C
FLY2
= 1
F
V
OUT
V
FB
= 3.4V
T
A
= 25
C
V
IN
= 3V
V
IN
= 3.2V
LOAD CURRENT (mA)
0
INPUT CURRENT (mA)
60
100
3202 G05
20
40
80
160
140
120
100
80
60
40
20
0
V
IN
= 3.6V
C
IN
= C
OUT
= C
FLY1
= C
FLY2
= 1
F
T
A
= 25
C
V
OUT
= 4.5V
V
OUT
= 4V
SUPPLY VOLTAGE (V)
2.7
OSCILLATOR FREQUENCY (MHz)
1.9
1.7
1.5
1.3
1.1
0.9
3.0
3.3
3.6
3.9
3202 G06
4.2
4.5
T
A
= 85
C
T
A
= 40
C
T
A
= 25
C
4
LTC3202
3202fa
D1, D0 (Pin 1, 10): Control Inputs. D0 and D1 determine
the set point voltage of the FB pin (see Table 1).
FB (Pin 2): FB is the Feedback Input for the Regulation
Control Loop.
V
OUT
(Pin 3): V
OUT
is the Output of the Charge Pump. A low
impedance 1
F X5R or X7R ceramic capacitor is required
from V
OUT
to GND.
V
IN
(Pin 4): Input Supply Voltage. V
IN
should be bypassed
with a 1
F to 4.7
F low impedance ceramic capacitor.
U
U
U
PI FU CTIO S
GND (Pin 5): Ground for the Charge Pump and Control
Circuitry. This pin should be connected directly to a low
impedance ground plane.
C2
, C1
, C1
+
, C2
+
(Pin 6, 7, 8, 9): Charge Pump Flying
Capacitor Pins. A 1
F X5R or X7R ceramic capacitor
should be connected from C1
+
to C1
and from C2
+
to
C2
.
PGND (Pin 11, Exposed Pad DFN Only): Power Ground
for the Charge Pump. This pin must be connected directly
to a low impedance ground plane.
Short-Circuit Current vs Supply
Voltage
V
OUT
Soft-Start Ramp
Input and Output Ripple
INPUT SUPPLY (V)
2.7
OUTPUT CURRENT (mA)
300
280
260
240
220
200
180
3.0
3.3
3.6
3.9
4.2
4.5
3202 G07
C
FLY
= 1
F
V
FB
= 0V
V
OUT
= 0V
T
A
= 25
C
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
V
D0, D1
2V/DIV
V
OUT
1V/DIV
200
s/DIV
V
IN
= 3.6V
C
OUT
= 1
F
3202 G08
V
IN
(AC COUPLED)
20mV/DIV
V
OUT
(AC COUPLED)
20mV/DIV
500ns/DIV
V
IN
= 3.6V
C
IN
= C
OUT
= 1
F
I
OUT
= 60mA
3202 G09
5
LTC3202
3202fa
SI PLIFIED
W
BLOCK DIAGRA
W
+
3202 BD
SOFT-START AND
SHUTDOWN
CONTROL
1.5MHz
OSCILLATOR
2-BIT
DAC
8
4
3
2
1
10
7
9
6
FB
VIN
VOUT
5, 11 GND
C2
C2
+
C1
C1
+
D0
D1
6
LTC3202
3202fa
Figure 1. Current Control Mode
3202 F01
LTC3202
V
OUT
FB
GND
1
F
I
LED
=
V
FB
R
X
5, 11
3
2
R
X
R
X
OPERATIO
U
The LTC3202 uses a fractional conversion switched ca-
pacitor charge pump to boost V
OUT
to as much as 1.5 times
the input voltage. A two-phase nonoverlapping clock acti-
vates the charge pump switches. On the first phase of the
clock the flying capacitors are charged in series from V
IN
.
On the second phase of the clock they are connected in
parallel and stacked on top of V
IN
. This sequence of
charging and discharging the flying capacitors continues
at a free running frequency of 1.5MHz (typ).
Regulation is achieved by sensing the voltage at the FB pin
and modulating the charge pump strength based on the
error signal. The control pins, D0 and D1, program the set
point of the internal digital-to-analog converter. The regu-
lation loop will increase V
OUT
until FB comes to balance at
the set-point voltage. Table 1 shows the regulation voltage
as a function of D0 and D1.
Table 1. Feedback Control Voltage Settings
D1
D0
Feedback Set Point Voltage
0
0
Shutdown
0
1
0.2V
1
0
0.4V
1
1
0.6V
In shutdown mode all circuitry is turned off and the
LTC3202 draws only leakage current from the V
IN
supply.
Furthermore, V
OUT
is disconnected from V
IN
. The D0 and
D1 pins are CMOS inputs with a threshold voltage of
approximately 0.8V. The LTC3202 is in shutdown when a
logic low is applied to both D0 and D1. Since the D0 and D1
pins are high impedance CMOS inputs they should never
be allowed to float. To ensure that their states are defined
they must always be driven with valid logic levels.
Shutdown Current
Output voltage detection circuitry will draw a current of
5
A when the LTC3202 is in shutdown. This current will be
eliminated when the output voltage (V
OUT
) is at 0V. To
ensure that V
OUT
is at 0V in shutdown a bleed resistor can
be used from V
OUT
to GND. 10k to 100k is acceptable.
Short-Circuit/Thermal Protection
The LTC3202 has built-in short-circuit current limiting as
well as over temperature protection. During short-circuit
conditions it will automatically limit its output current to
approximately 250mA. At higher temperatures, or if the
input voltage is high enough to cause excessive self
heating on-chip, thermal shutdown circuitry will
shut down the charge pump when the junction tempera-
ture exceeds approximately 160
C. It will reenable the
charge pump once the junction temperature drops back to
approximately 155
C. The LTC3202 will cycle in and out of
thermal shutdown indefinitely without latchup or damage
until the short-circuit on V
OUT
is removed.
Soft-Start
To prevent excessive current flow at V
IN
during start-up,
the LTC3202 has built-in soft-start circuitry. Soft-start is
achieved by increasing the amount of current available to
the output charge storage capacitor linearly over a period
of approximately 500
s.
The soft-start feature activates any time an input, D0 or D1,
changes state. This will prevent large inrush current
during initial start-up as well as when the feedback setting
is changed from one value to the next. Note that the set
point voltage will drop to zero during the soft-start period.
Under heavy load conditions there may be observable
droop at V
OUT
until the soft-start circuit catches up.
Programming the LTC3202 for Voltage or Current
The LTC3202 can be configured to control either a voltage
or a current. In white LED applications the LED current is
programmed by the ratio of the feedback set point voltage
and a sense resistor as shown in Figure 1. The current of
the remaining LEDs is controlled by virtue of their similar-
ity to the reference LED and the ballast voltage across the
sense resistor.
(Refer to Simplified Block Diagram)
7
LTC3202
3202fa
In this configuration the feedback factor (
V
FB
/
V
OUT
) will
be very near unity since the small signal LED impedance
will be considerably less than the current setting resistor
R
X
. Thus, this configuration will have the highest
loop gain
giving it the lowest closed-loop output resistance. Like-
wise it will also require the largest amount of output
capacitance to preserve stability.
For fixed voltage applications, the output voltage can be
set by the ratio of two resistors and the feedback control
voltage as shown in Figure 2. The output voltage is given
by the set point voltage times the gain factor 1 + R
1
/R
2
.
Note that the closed-loop output resistance will increase in
proportion to the loop gain consumed by the resistive
divider ratio. For example, if the resistor ratio is 2:1 giving
a gain of 3, the closed-loop output resistance will be about
3 times higher than its nominal gain of 1 value. Given that
the closed-loop output resistance is about 0.35
with a
gain of 1, the closed-loop output resistance will be about
1
when using a gain of 3.
Figure 2. Voltage Control Mode
Charge Pump Strength
Figure 3 shows how the LTC3202 can be modeled as a
Thevenin equivalent circuit to determine the amount of
current available from the effective input voltage, 1.5V
IN
and the effective open-loop output resistance, R
OL
.
Figure 3. Equivalent Open-Loop Circuit
Figure 4. Typical R
OL
vs Temperature
3202 F02
LTC3202
V
OUT
FB
GND
V
OUT
= V
FB
(1 + )
R1
R2
1
F
R1
R2
5, 11
3
2
3202 F03
+
1.5V
IN
R
OL
V
OUT
+
OPERATIO
U
(Refer to Simplified Block Diagram)
From Figure 3 the available current is given by:
I
V
V
R
OUT
IN
OUT
OL
=
1 5
.
Typical values of R
OL
as a function of temperature are
shown in Figure 4.
When using the LTC3202 in voltage control mode, any of
the three voltage settings (0.2V, 0.4V or 0.6V) can be used
as the set point voltage. For optimum noise performance
and lowest closed-loop output resistance the highest
voltage setting will likely be the most desirable.
Typical values for total voltage divider resistance can
range from several k
s up to 1M
.
TEMPERATURE (
C)
40
OUTPUT RESISTANCE (
)
4.8
4.6
4.4
4.2
4.0
3.8
60
3202 F04
15
10
35
85
V
FB
= 0
I
L
= 100mA
C1 = C2 = 1
F
R
OL
= (1.5V
IN
V
OUT
)/I
L
V
IN
= 2.7V
V
IN
= 3.6V
8
LTC3202
3202fa
R
OL
is dependent on a number of factors including the
switching term, 1/(2f
OSC
C
FLY
), internal switch resis-
tances and the nonoverlap period of the switching circuit.
However, for a given R
OL
, the amount of current available
will be directly proportional to the
advantage voltage
1.5V
IN
V
OUT
. This voltage can typically be quite small.
Consider the example of driving white LEDs from a
3.1V supply. If the LED forward voltage is 3.8V and the
0.6V V
FB
setting is used, the advantage voltage is 3.1V
1.5V 3.8V 0.6V or only 250mV. However if the input
voltage is raised to 3.2V the advantage voltage jumps to
400mV--a 60% improvement in available strength! Note
that a similar improvement in advantage voltage can be
achieved by operating the LTC3202 at a lower voltage
setting such as the 0.4V setting.
V
IN
, V
OUT
Capacitor Selection
The style and value of capacitors used with the LTC3202
determine several important parameters such as regulator
control loop stability, output ripple, charge pump strength
and minimum start-up time.
To reduce noise and ripple, it is recommended that low
equivalent series resistance (ESR) ceramic capacitors be
used for both C
IN
and C
OUT
. Tantalum and aluminum
capacitors are not recommended because of their high ESR.
The value of C
OUT
directly controls the amount of output
ripple for a given load current. Increasing the size of C
OUT
will reduce the output ripple at the expense of higher
minimum turn-on time and higher start-up current. The
peak-to-peak output ripple is approximately given by the
expression:
V
I
f
C
RIPPLEP P
OUT
OSC
OUT
-
3
Where f
OSC
is the LTC3202's oscillator frequency (typi-
cally 1.5MHz) and C
OUT
is the output charge storage
capacitor.
Both the style and value of the output capacitor can
significantly affect the stability of the LTC3202. As shown
in the block diagram, the LTC3202 uses a control loop to
adjust the strength of the charge pump to match the
current required at the output. The error signal of this loop
is stored directly on the output charge storage capacitor.
The charge storage capacitor also serves to form the
dominant pole for the control loop. To prevent ringing or
instability, it is important for the output capacitor to
maintain at least 0.6
F of capacitance over all conditions.
Likewise, excessive ESR on the output capacitor will tend
to degrade the loop stability of the LTC3202. The closed-
loop output resistance of the LTC3202 is designed to be
0.35
. For a 100mA load current change, the feedback
voltage will change by about 35mV. If the output capacitor
has 0.35
or more of ESR the closed-loop frequency
response will cease to roll-off in a simple one-pole fashion
and poor load transient response or instability could
result. Multilayer ceramic chip capacitors typically have
exceptional ESR performance and combined with a tight
board layout should yield very good stability and load
transient performance.
As the value of C
OUT
controls the amount of output ripple,
the value of C
IN
controls the amount of ripple present at the
input pin (V
IN
). The input current to the LTC3202 will be
relatively constant while the charge pump is on either the
input charging phase or the output charging phase but will
drop to zero during the clock nonoverlap times. Since the
nonoverlap time is small (~25ns) these missing "notches"
will result in only a small perturbation on the input power
supply line. Note that a higher ESR capacitor such as
tantalum will have higher input noise due to the input
current change times the ESR. Therefore ceramic capaci-
tors are again recommended for their exceptional ESR
performance.
Further input noise reduction can be achieved by powering
the LTC3202 through a very small series inductor as
shown in Figure 5. A 10nH inductor will reject the fast
current notches, thereby presenting a nearly constant
current load to the input power supply. For economy the
10nH inductor can be fabricated on the PC board with
about 1cm (0.4") of PC board trace.
OPERATIO
U
9
LTC3202
3202fa
Flying Capacitor Selection
Warning: A polarized capacitor such as tantalum or alumi-
num should never be used for the flying capacitors since
their voltage can reverse upon start-up of the LTC3202.
Ceramic capacitors should always be used for the flying
capacitors.
The flying capacitor controls the strength of the charge
pump. In order to achieve the rated output current it is
necessary to have at least 0.7
F of capacitance for each of
the flying capacitors.
Capacitors of different materials lose their capacitance
with higher temperature and voltage at different rates. For
example, a ceramic capacitor made of X7R material will
retain most of its capacitance from 40
C to 85
C whereas
a Z5U or Y5V style capacitor will lose considerable capaci-
tance over that range. Z5U and Y5V capacitors may also
have a very poor voltage coefficient causing them to lose
60% or more of their capacitance when the rated voltage
is applied. Therefore, when comparing different capaci-
tors it is often more appropriate to compare the amount of
achievable capacitance for a given case size rather than
comparing the specified capacitance value. For example,
over rated voltage and temperature conditions, a 1
F, 10V,
Y5V ceramic capacitor in a 0603 case may not provide any
more capacitance than a 0.22
F, 10V, X7R available in the
same 0603 case. The capacitor manufacturer's data sheet
should be consulted to determine what value of capacitor
is needed to ensure minimum capacitances at all tempera-
tures and voltages.
Table 2 shows a list of ceramic capacitor manufacturers
and how to contact them:
Table 2 Recommended Capacitor Vendors
AVX
www.avxcorp.com
Kemet
www.kemet.com
Murata
www.murata.com
Taiyo Yuden
www.t-yuden.com
Vishay
www.vishay.com
For very light load applications the flying capacitor may be
reduced to save space or cost. The theoretical minimum
output resistance of a 2:3 fractional charge pump is given
by:
R
V
V
I
f
C
OL MIN
IN
OUT
OUT
SC FLY
(
)
.
=
1 5
1
2
0
Where f
OSC
is the switching frequency (1.5MHz typ) and
C
FLY
is the value of the flying capacitors. Note that the
charge pump will typically be weaker than the theoretical
limit due to additional switch resistance, however for very
light load applications the above expression can be used
as a guideline in determining a starting capacitor value.
Power Efficiency
The power efficiency (
) of the LTC3202 is similar to that
of a linear regulator with an effective input voltage of 1.5
times the actual input voltage. This occurs because the
input current for a 2:3 fractional charge pump is approxi-
mately 1.5 times the load current. In an ideal regulating 2:3
charge pump the power efficiency would be given by:
IDEAL
OUT
IN
OUT
OUT
IN
OUT
OUT
IN
P
P
V
I
V
I
V
V
=
=
.
3
2
1 5
At moderate to high output power the switching losses
and quiescent current of the LTC3202 are negligible and
the expression above is valid. For example with V
IN
= 3.2V,
I
OUT
= 80mA and V
OUT
regulating to 4.2V the measured
efficiency is 82% which is just under the theoretical 87.5%
calculation.
OPERATIO
U
Figure 5. 10nH Inductor Used for Input Noise Reduction
3202 F05
LTC3202
V
IN
V
IN
GND
5, 11
4
0.1
F
1
F
10nH
10
LTC3202
3202fa
Figure 6. Recommended Layouts
V
OUT
GND
V
IN
Layout Considerations
Due to its high switching frequency and the transient
currents produced by the LTC3202, careful board layout is
necessary. A true ground plane and short connections to
all capacitors will improve performance and ensure proper
regulation under all conditions. Figure 6 shows the recom-
mended layout configurations.
The flying capacitor pins C1
+
, C2
+
, C1
and C2
will have
very high edge rate waveforms. The large dv/dt on these
pins can couple energy capacitively to adjacent printed
circuit board runs. Magnetic fields can also be generated
if the flying capacitors are not close to the LTC3202 (i.e.
the loop area is large). To decouple capacitive energy
transfer, a Faraday shield may be used. This is a grounded
PC trace between the sensitive node and the LTC3202
pins. For a high quality AC ground it should be returned to
a solid ground plane that extends all the way to the
LTC3202.
OPERATIO
U
Figure 7. Alternative Brightness Control
Thermal Management
For higher input voltages and maximum output current
there can be substantial power dissipation in the LTC3202.
If the junction temperature increases above approxi-
mately 160
C the thermal shutdown circuitry will auto-
matically deactivate the output. To reduce the maximum
junction temperature, a good thermal connection to the
PC board is recommended. Connecting the GND pin (Pin
5 and Pin 11 on the DFN package) to a ground plane, and
maintaining a solid ground plane under the device can
reduce the thermal resistance of the package and PC
board considerably.
Brightness Control Using Pulse Width Modulation
An alternative approach to dimming is to use pulse width
modulation rather than the internal digital to analog con-
verter. By connecting both the D0 and D1 pins to a PWM
signal, continuous brightness control can be achieved.
Frequencies from 100Hz to 500Hz are acceptable with a
1
F to 4.7
F output capacitor.
V
D0, D1
t
10
1
D0
D1
LTC3202
3202 F07
V
OUT
V
IN
GND
3202 F06
D1
D0
11
LTC3202
3202fa
PACKAGE DESCRIPTIO
U
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 represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
MS Package
10-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1661)
DD Package
10-Lead Plastic DFN (3mm
3mm)
(Reference LTC DWG # 05-08-1699)
3.00
0.10
(4 SIDES)
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2)
2. ALL DIMENSIONS ARE IN MILLIMETERS
3. 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
4. EXPOSED PAD SHALL BE SOLDER PLATED
0.38
0.10
BOTTOM VIEW--EXPOSED PAD
1.65
0.10
(2 SIDES)
0.75
0.05
R = 0.115
TYP
2.38
0.10
(2 SIDES)
1
5
10
6
PIN 1
TOP MARK
0.200 REF
0.00 0.05
(DD10) DFN 0103
0.25
0.05
2.38
0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
1.65
0.05
(2 SIDES)
2.25
0.05
0.50
BSC
0.55
0.05
3.35
0.05
PACKAGE
OUTLINE
0.25
0.05
0.50 BSC
MSOP (MS) 0603
0.53
0.152
(.021
.006)
SEATING
PLANE
0.18
(.007)
1.10
(.043)
MAX
0.17 0.27
(.007 .011)
TYP
0.127
0.076
(.005
.003)
0.86
(.034)
REF
0.50
(.0197)
BSC
1 2 3 4 5
4.90
0.152
(.193
.006)
0.497
0.076
(.0196
.003)
REF
8
9
10
7 6
3.00
0.102
(.118
.004)
(NOTE 3)
3.00
0.102
(.118
.004)
(NOTE 4)
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
0.254
(.010)
0
6
TYP
DETAIL "A"
DETAIL "A"
GAUGE PLANE
5.23
(.206)
MIN
3.20 3.45
(.126 .136)
0.889
0.127
(.035
.005)
RECOMMENDED SOLDER PAD LAYOUT
0.305
0.038
(.0120
.0015)
TYP
0.50
(.0197)
BSC
12
LTC3202
3202fa
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
q
FAX: (408) 434-0507
q
www.linear.com
LINEAR TECHNOLOGY CORPORATION 2001
LT/TP 0803 1K PRINTED IN USA
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3202 TA02
LTC3202
V
OUT
FB
GND
C4
1
F
C1
1
F
5, 11
3
2
C2
C2
+
C1
C1
+
V
IN
3V TO 4.5V
10
4
1
36
36
36
36
36
36
C3
1
F
C2
1
F
D0
D1
V
IN
8
7
9
6
ON
OFF
R2
3.9k
R1
1k
V
C
= 0V TO 3V
I
LED
=
(
1 +
)
0.6V
36
R1
R2
V
C
36
R1
R2
U
TYPICAL APPLICATIO
LED Driver with Linear Brightness Control
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