LTC3202
Low Noise, High Efficiency
Charge Pump for White LEDs
FEATURES
s
s
s
s
s
s
s
s
s
s
s
DESCRIPTIO
Low Noise Constant Frequency Operation
25% Less Input Current Than Doubler Charge Pump
High Output Current: Up To 125mA
Small Application Circuit
Regulated Output Voltage or Current
Automatic Soft-Start
V
IN
Range: 2.7V to 4.5V
No Inductors
1.5MHz Switching Frequency
I
CC
< 1µA in Shutdown
Available in 10-Pin MSOP and 3mm
×
3mm
DFN Packages
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
than1µA.
The LTC3202 is available in the 10-pin MSOP and 3mm
×
3mm DFN packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s
s
White LED Backlighting
Programmable Boost Current Source
TYPICAL APPLICATIO
C2
1µF
C3
1µF
Programmable White LED Power Supply
Input and Output Ripple
V
IN
(AC COUPLED)
20mV/DIV
8
C1
+
10
CURRENT
PROGRAMMING
V
IN
3V TO 4.5V
C1
1µF
1
4
D0
D1
V
IN
7
C1
–
9
C2
+
6
C2
–
V
OUT
0mA TO 125mA
TOTAL CURRENT
3
LTC3202
FB
GND
5, 11
2
C4
1µF
36Ω
36Ω
36Ω
36Ω
36Ω
36Ω
V
OUT
(AC COUPLED)
20mV/DIV
500ns/DIV
V
IN
= 3.6V
C
IN
= C
OUT
= 1µF
I
OUT
= 60mA
3202 G09
C1, C2, C3, C4 = MURATA GRM 39X5R105K6.3 OR TAIYO YUDEN JMK107BJ105MA
3202 TA01
U
3202fa
U
U
1
LTC3202
ABSOLUTE
AXI U RATI GS
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
PACKAGE/ORDER I FOR ATIO
TOP VIEW
D1 1
FB 2
V
OUT
3
V
IN
4
GND 5
10
9
8
7
6
D0
C2
+
C1
+
C1
–
C2
–
ORDER PART
NUMBER
LTC3202EMS
MS PART MARKING
LTWL
MS PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 150°C,
θ
JA
= 120°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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.
PARAMETER
Input Power Supply
V
IN
Operating Voltage
I
CC
Operating Current
I
SHDN
Shutdown Current
Feedback Pin Set Points
0.2V Setting Feedback Voltage
0.4V Setting Feedback Voltage
0.6V Setting Feedback Voltage
I
FB
Charge Pump
R
OL
Open Loop Output Impedance (1.5V
IN
– V
OUT
)/I
OUT
V
OUT
Load Regulation (∆V
OUT
/∆I
OUT
)
CLK Frequency
D0, D1
High Level Input Voltage (V
IH
)
Low Level Input Voltage (V
IL
)
Input Current (I
IH
)
Input Current (I
IL
)
DO, D1 = V
IN
DO, D1 = 0V
q
q
q
q
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
I
OUT
= 0mA, V
OUT
= 3.6V, V
IN
= D0 = D1 = 4.5V
V
OUT
= 0V
D0 = 1, D1 = 0, I
OUT
= 0mA, V
IN
= 3.6V
D0 = 0, D1 = 1, I
OUT
= 0mA, V
IN
= 3.6V
D0 = 1, D1 = 1, I
OUT
= 0mA, V
IN
= 3.6V
V
FB
= 0.8V
V
IN
= 3.3V, V
OUT
= 4.4V, V
FB
= 0
I
OUT
= 10mA to 90mA,
∆V
FB
/∆V
OUT
= 1
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.
2
U
U
W
W W
U
W
(Note 1)
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
TOP VIEW
D1
FB
V
OUT
V
IN
SGND
1
2
3
4
5
11
10 D0
9 C2
+
8 C1
+
7 C1
–
6 C2
–
ORDER PART
NUMBER
LTC3202EDD
DD PART MARKING
LABB
DD PACKAGE
10-LEAD (3mm
×
3mm) PLASTIC DFN
T
JMAX
= 150°C,
θ
JA
= 44°C/W,
θ
JC
= 3°C/W
EXPOSED PAD IS PGND (PIN 11) MUST BE
CONNECTED TO GROUND PLANE
MIN
2.7
TYP
MAX
4.5
UNITS
V
mA
µA
mV
mV
mV
nA
Ω
mV/mA
MHz
V
q
q
2.5
5
1
q
q
q
q
188
380
570
–50
200
400
600
212
420
630
50
q
4.5
0.35
1.5
1.3
6
0.4
–1
–1
1
1
V
µA
µA
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.
3202fa
LTC3202
TYPICAL PERFOR A CE CHARACTERISTICS
V
FB
Set Point vs Input Supply
(200mV Setting)
0.21
I
LOAD
= 20µA
V
D0
= V
IN
V
D1
= 0V
SET POINT (V)
T
A
= 85°C
0.20
T
A
= 25°C
SET POINT (V)
0.19
2.7
3.0
3.3
3.6
3.9
INPUT SUPPLY (V)
V
FB
Set Point vs Input Supply
(600mV Setting)
0.63
I
LOAD
= 60µA
V
D0
= V
D1
= V
IN
0.8
0.7
FEEDBACK VOLTAGE (V)
SET POINT (V)
T
A
= 25°C, 85°C
0.60
T
A
= –40°C
0.57
2.7
3.0
3.3
3.6
3.9
INPUT SUPPLY (V)
Input Current vs Load Current
160
140
INPUT CURRENT (mA)
OSCILLATOR FREQUENCY (MHz)
V
IN
= 3.6V
C
IN
= C
OUT
= C
FLY1
= C
FLY2
= 1µF
T
A
= 25°C
120
100
80
V
OUT
= 4V
60
40
20
0
0
V
OUT
= 4.5V
20
80
60
LOAD CURRENT (mA)
U W
40
V
FB
Set Point vs Input Supply
(400mV Setting)
0.42
I
LOAD
= 40µA
V
D0
= 0V
V
D1
= V
IN
T
A
= 25°C
T
A
= 85°C
0.40
T
A
= –40°C
T
A
= –40°C
4.2
4.5
3202 G01
0.38
2.7
3.0
3.3
3.6
3.9
INPUT SUPPLY (V)
4.2
4.5
3202 G02
V
FB
vs Load Current
V
D0
= V
D1
= V
IN
C
IN
= C
OUT
= C
FLY1
= C
FLY2
= 1µF
V
OUT
– V
FB
= 3.4V
T
A
= 25°C
V
IN
= 3.2V
V
IN
= 3V
0.6
0.5
0.4
0.3
0.2
4.2
4.5
3202 G03
0
25
50
75
100
LOAD CURRENT (mA)
125
150
3202 G04
Oscillator Frequency vs Supply
Voltage
1.9
1.7
T
A
= –40°C
T
A
= 25°C
T
A
= 85°C
1.5
1.3
1.1
0.9
100
3202 G05
2.7
3.0
3.3
3.6
3.9
SUPPLY VOLTAGE (V)
4.2
4.5
3202 G06
3202fa
3
LTC3202
TYPICAL PERFOR A CE CHARACTERISTICS
Short-Circuit Current vs Supply
Voltage
300
280
C
FLY
= 1µF
V
FB
= 0V
V
OUT
= 0V
T
A
= 25°C
OUTPUT CURRENT (mA)
V
OUT
Soft-Start Ramp
V
IN
(AC COUPLED)
20mV/DIV
V
D0, D1
2V/DIV
V
OUT
1V/DIV
V
IN
= 3.6V
C
OUT
= 1µF
PI FU CTIO S
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 1µF 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 1µF to 4.7µF low impedance ceramic capacitor.
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 1µF 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.
4
U W
260
240
220
200
180
2.7
3.0
3.3
3.6
3.9
INPUT SUPPLY (V)
4.2
4.5
3202 G07
Input and Output Ripple
V
OUT
(AC COUPLED)
20mV/DIV
200µs/DIV
3202 G08
500ns/DIV
V
IN
= 3.6V
C
IN
= C
OUT
= 1µF
I
OUT
= 60mA
3202 G09
U
U
U
3202fa
LTC3202
SI PLIFIED BLOCK DIAGRA
FB 2
VIN 4
7
C1
–
VOUT 3
9
W
–
10 D0
2-BIT
DAC
+
W
1 D1
SOFT-START AND
SHUTDOWN
CONTROL
1.5MHz
OSCILLATOR
8 C1
+
C2
+
6
C2
–
3202 BD
5, 11 GND
3202fa
5
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