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Datasheet LTC3202 PDF ( 特性, スペック, ピン接続図 )

部品番号 LTC3202
部品説明 Low Noise/ High Efficiency Charge Pump for White LEDs
メーカ Linear Technology
ロゴ Linear Technology ロゴ 
プレビュー
Total 13 pages
		
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LTC3202 Datasheet, LTC3202 PDF,ピン配置, 機能
LTC3202
Low Noise, High Efficiency
Charge Pump for White LEDs
FEATURES
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 VIN Range: 2.7V to 4.5V
s No Inductors
s 1.5MHz Switching Frequency
s ICC < 1µA in Shutdown
s Available in 10-Pin MSOP and 3mm × 3mm
DFN Packages U
APPLICATIO S
s White LED Backlighting
s Programmable Boost Current Source
DESCRIPTIO
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
VIN and VOUT) 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 VOUT 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 VIN 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.
TYPICAL APPLICATIO
Programmable White LED Power Supply
C2 C3
1µF 1µF
8 79 6
C1+
10 D0
CURRENT
C1
C2+
C2
0mA TO 125mA
3 TOTAL CURRENT
VOUT
PROGRAMMING 1 D1 LTC3202
VIN
3V TO 4.5V
C1
1µF
4 VIN
2
FB
GND
5, 11
C4
1µF
36
36
36
36
3636
C1, C2, C3, C4 = MURATA GRM 39X5R105K6.3 OR TAIYO YUDEN JMK107BJ105MA
3202 TA01
Input and Output Ripple
VIN
(AC COUPLED)
20mV/DIV
VOUT
(AC COUPLED)
20mV/DIV
VIN = 3.6V
500ns/DIV
CIN = COUT = 1µF
IOUT = 60mA
3202 G09
3202fa
1

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LTC3202 pdf, ピン配列
TYPICAL PERFOR A CE CHARACTERISTICS
LTC3202
VFB Set Point vs Input Supply
(200mV Setting)
0.21
ILOAD = 20µA
VD0 = VIN
VD1 = 0V
TA = 85°C
TA = 25°C
0.20
TA = –40°C
VFB Set Point vs Input Supply
(400mV Setting)
0.42
ILOAD = 40µA
VD0 = 0V
VD1 = VIN
TA = 85°C
TA = 25°C
0.40
TA = –40°C
0.19
2.7 3.0 3.3 3.6 3.9 4.2 4.5
INPUT SUPPLY (V)
3202 G01
VFB Set Point vs Input Supply
(600mV Setting)
0.63
ILOAD = 60µA
VD0 = VD1 = VIN
TA = 25°C, 85°C
0.60
TA = –40°C
0.57
2.7 3.0 3.3 3.6 3.9 4.2 4.5
INPUT SUPPLY (V)
3202 G03
Input Current vs Load Current
160
VIN = 3.6V
140
CIN = COUT = CFLY1 = CFLY2 = 1µF
TA = 25°C
120
100
VOUT = 4.5V
80
VOUT = 4V
60
40
20
0
0 20 40 60 80 100
LOAD CURRENT (mA)
3202 G05
0.38
2.7 3.0 3.3 3.6 3.9 4.2 4.5
INPUT SUPPLY (V)
3202 G02
VFB vs Load Current
0.8
VD0 = VD1 = VIN
CIN = COUT = CFLY1 = CFLY2 = 1µF
0.7 VOUT – VFB = 3.4V
TA = 25°C
0.6 VIN = 3.2V
0.5
VIN = 3V
0.4
0.3
0.2
0
25 50 75 100 125 150
LOAD CURRENT (mA)
3202 G04
Oscillator Frequency vs Supply
Voltage
1.9
1.7 TA = –40°C
1.5 TA = 25°C
1.3 TA = 85°C
1.1
0.9
2.7
3.0 3.3 3.6 3.9 4.2 4.5
SUPPLY VOLTAGE (V)
3202 G06
3202fa
3


3Pages


LTC3202 電子部品, 半導体
LTC3202
U
OPERATIO (Refer to Simplified Block Diagram)
The LTC3202 uses a fractional conversion switched ca-
pacitor charge pump to boost VOUT 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 VIN.
On the second phase of the clock they are connected in
parallel and stacked on top of VIN. 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 VOUT 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
00
Shutdown
01
0.2V
10
0.4V
11
0.6V
In shutdown mode all circuitry is turned off and the
LTC3202 draws only leakage current from the VIN supply.
Furthermore, VOUT is disconnected from VIN. 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
5µA when the LTC3202 is in shutdown. This current will be
eliminated when the output voltage (VOUT) is at 0V. To
ensure that VOUT is at 0V in shutdown a bleed resistor can
be used from VOUT 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
6
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 VOUT is removed.
Soft-Start
To prevent excessive current flow at VIN 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 500µs.
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 VOUT 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.
3
VOUT
LTC3202
2
FB
GND
5, 11
ILED =
VFB
RX
•••
1µF RX
RX
3202 F01
Figure 1. Current Control Mode
3202fa

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