LTC3203 [Linear]
500mA Output Current Low Noise Dual Mode Step-Up Charge Pumps; 500mA输出电流,低噪声双模式升压电荷泵型号: | LTC3203 |
厂家: | Linear |
描述: | 500mA Output Current Low Noise Dual Mode Step-Up Charge Pumps |
文件: | 总16页 (文件大小:237K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
500mA Output Current
Low Noise Dual Mode
Step-Up Charge Pumps
U
FEATURES
DESCRIPTIO
TheLTC®3203/LTC3203-1/LTC3203B/LTC3203B-1arelow
noise, high efficiency charge pump DC/DC converters
capable of driving loads up to 500mA from a 2.7V to 5.5V
input. Low external parts count (two flying capacitors and
bypass capacitors at VIN and VOUT) make the LTC3203
family ideally suited for small, battery-powered applica-
tions.
■
Selectable Dual Mode Operation: 1:1.5 or 1:2
■
High Output Current: Up to 500mA
■
Low Noise Constant Frequency (1MHz/0.9MHz)
Operation*
VIN Range: 2.7V to 5.5V
■
■
Adjustable Output Voltage (LTC3203/LTC3203B)
■
User Selectable Fixed Output Voltages: 4.5V or 5V
(LTC3203-1 and LTC3203B-1)
Built-in soft-start circuitry prevents excessive inrush
current during start-up. High switching frequency enables
the use of small external capacitors. The LTC3203/
LTC3203-1 feature Burst Mode operation at light load to
achieve high efficiency whereas the LTC3203B/
LTC3203B-1 operate at constant frequency to achieve
lowest noise operation.
Burst Mode® Operation with
■
IQ ~ 120µA (LTC3203/LTC3203-1)
■
Constant Freqency Operation at All Loads
(LTC3203B/LTC3203B-1)
■
Soft-Start Limits Inrush Current at Turn-On
■
Short-Circuit/Thermal Protection
■
Shutdown Disconnects Load from Input
■
The LTC3203-1/LTC3203B-1 have a user selectable fixed
output voltage of 4.5V or 5V to power LEDs or logic
circuits.TheFBpinoftheLTC3203/LTC3203Bcanbeused
toprogramthedesiredoutputvoltage.Thepartsareshort-
circuit and overtemperature protected and are available in
a low profile (3mm × 3mm) DFN package.
Shutdown Current: < 1µA
■
Available in a 10-pin (3mm × 3mm) DFN Package
U
APPLICATIO S
■
High Current LED Backlight Supply for
Cellphones/PDAs
, 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.
*Protected by U.S. Patents including 6411531.
■
Cellphone Camera Light Supply
■
General Purpose 3.3V or Li-Ion to 5V Supply
■
USB ON THE GO(OTG) Devices
U
TYPICAL APPLICATIO
Efficiency vs V at 300mA Load Current
100
IN
OUTPUT PROGRAMMING
ON/OFF
90
80
70
60
50
40
30
20
10
0
V
V
= 5V
OUT
SHDN
SEL
LTC3203-1
V
V
= 4.5V
OUT
V
OUT
V
IN
V
IN
OUT
500mA
10µF
+
+
2.2µF
C1
C1
C2
2.2µF
2.2µF
–
–
C2
GND
R1*
MODE
3203 F02
100k
I
V
V
*R1
OUT(MAX)
SEL
OUT
300mA LOW 4.5V 316k
300mA HIGH 5V 357k
500mA LOW 4.5V 357k
500mA HIGH 5V 402k
2.5
3
4
(V)
4.5
5
5.5
3.5
V
IN
3203 G05
32031fa
1
LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
W W
U W
U
W
U
ABSOLUTE AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
(Note 1)
TOP VIEW
VIN, VOUT to GND ......................................... –0.3V to 6V
MODE, VSEL/FB, SHDN ..................... –0.3V to VIN +0.3V
+
–
C2
1
2
3
4
5
10 C1
V
9
8
7
6
GND
OUT
V
OUT Short Circuit Duration ............................. Indefinite
+
–
C1
C2
11
IOUT (Note 2)....................................................... 500mA
Operating Temperature Range (Note 3) ... –40°C to 85°C
Storage Temperature Range .................. –65°C to 125°C
SHDN
/FB*
V
IN
V
SEL
MODE
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
TJMAX = 125°C,θJA = 44°C/W,θJC = 3°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
*VSEL ON LTC3203-1/LTC3203B-1. FB ON LTC3203/LTC3203B
ORDER PART NUMBER
DD PART MARKING
LTC3203EDD
LTC3203EDD-1
LBQK
LCFH
LCGY
LCGX
LTC3203BEDD-1
LTC3203BEDD
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full specified temperature
range, otherwise specifications are at 25°C. V = 3.6V, C1 = C2 = 2.2µF unless otherwise specified.
IN
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
LTC3203/LTC3203-1/LTC3203B/LTC3203B-1
V
Input Voltage Range
Shutdown Current
●
●
2.7
5.5
1
V
IN
I
SHDN = 0V, V
= 0V
µA
SHDN
OUT
R
OL
Open Loop Output
Impedance
2x Mode (Note 4), V = 2.7V, V = 4.5V
OUT
2.0
1.5
3.0
2.6
Ω
Ω
IN
1.5x Mode (Note 4), V = 3.6V, V
= 4.5V
IN
OUT
f
CLK Frequency
Oscillator Free Running, 2x Mode
Oscillator Free Running, 1.5x Mode
1.0
0.9
MHz
MHz
OSC
V
V
V
V
MODE Input High Voltage
MODE Input Low Voltage
SHDN Input High Voltage
SHDN Input Low Voltage
MODE Input High Current
MODE Input Low Current
SHDN Input High Current
SHDN Input Low Current
●
●
●
●
●
●
●
●
0.874
0.788
1.3
0.91
0.82
0.946
0.852
V
V
MODEH
MODEL
SHDNH
SHDNL
MODEH
MODEL
SHDNH
SHDNL
V
0.4
1
V
I
I
I
I
–1
–1
–1
–1
µA
µA
µA
µA
1
1
1
32031fa
2
LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full specified temperature
range, otherwise specifications are at 25°C. V = 3.6V, C1 = C2 = 2.2
µF unless otherwise specified.
IN
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
LTC3203-1/LTC3203B-1
V
4.5V Output Voltage Range
SEL
V
IN
V
IN
V
IN
> 3.1V, I
> 2.9V, I
> 2.7V, I
< 500mA
< 350mA
< 250mA
4.32
4.32
4.32
4.5
4.5
4.5
4.68
4.68
4.68
V
V
V
OUT
OUT
OUT
OUT
(V = 0V) (Note 5)
●
●
5V Output Voltage Range
V
IN
V
IN
V
IN
> 3.1V, I
> 3.1V, I
> 2.7V, I
< 500mA
< 400mA
< 150mA
4.8
4.8
4.8
5
5
5
5.2
5.2
5.2
V
V
V
OUT
OUT
OUT
(V = V ) (Note 5)
●
●
SEL
IN
∆V /∆I
OUT OUT
V
Load Regulation
V
IN
V
IN
= 3.6V, I
= 100mA to 500mA, 2x Mode,
0.37
0.27
mV/mA
mV/mA
OUT
OUT
= 4V, I
= 100mA to 500mA, 1.5x Mode
OUT
I
No Load Operating Current
(LTC3203-1)
I
I
= 0mA, 2x Mode
= 0mA, 1.5x Mode
120
100
300
300
µA
µA
CC
OUT
OUT
No Load Operating Current
(LTC3203B-1)
I
I
= 0mA, 2x Mode
= 0mA, 1.5x Mode
9
7
mA
mA
OUT
OUT
V
V
V
V
V
V
Input High Voltage
Input Low Voltage
Input High Current
Input Low Current
●
●
●
●
1.3
V
V
VSELH
VSELL
VSELH
VSELL
SEL
SEL
SEL
SEL
0.4
1
I
I
–1
–1
µA
µA
1
LTC3203/LTC3203B
V
Feedback Servo Voltage
FB Input Current
I
= 0mA, 2.7V ≤ V ≤ 5.5V
●
●
0.88
–50
0.91
0.94
50
V
FB
OUT
IN
I
V
= 0.95V
nA
FB
FB
∆V /∆I
FB OUT
Load Regulation
(Refer to FB Pin)
I
I
= 100mA to 500mA, 2x Mode, V = 3.6V
0.08
0.06
mV/mA
mV/mA
OUT
OUT
IN
= 100mA to 500mA, 1.5x Mode, V = 4V
IN
I
No Load Operating Current
(LTC3203)
I
I
= 0mA, 2x Mode, 5V V Setting
OUT
120
100
300
300
µA
µA
CC
OUT
OUT
= 0mA, 1.5x Mode, 5V V
Setting
OUT
No Load Operating Current
(LTC3203B)
I
I
= 0mA, 2x Mode, 5V V
= 0mA, 1.5x Mode, 5V V
Setting
9
7
mA
mA
OUT
OUT
OUT
Setting
OUT
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: Output not in regulation (based on wafer sort):
R
OL
R
OL
≡ (2 • V – V )/I , 2x Mode
IN OUT OUT
≡ (1.5 • V – V )/I , 1.5x Mode
IN
OUT OUT
Note 5: Proper conversion mode, 1.5x or 2x, has to be chosen based on
to ensure output regulation.
Note 2: Based on long-term current density limitations.
R
OL
Note 3: The LTC3203/LTC3203-1/LTC3203B/LTC3203B-1 are guaranteed
to meet performance specifications from 0°C to 85°C. Specifications over
the –40°C to 85°C operating temperature range are assured by design,
characterization and correlation with statistical process controls.
32031fa
3
LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
U W
TYPICAL PERFOR A CE CHARACTERISTICS
T = 25
A
°
C, V = 3.6V, C1 = C2 = 2.2
µF unless otherwise specified
IN
V
vs Load Current
V
vs Supply Voltage
V
vs Load Current
OUT
OUT
OUT
(4.5V Output Setting)
(4.5V Output Setting)
(5V Output Setting)
4.65
4.60
4.55
4.50
4.45
4.40
4.35
4.30
4.25
5.5
5.3
5.1
4.9
4.7
4.5
4.3
4.1
3.9
3.7
3.5
4.8
4.6
4.4
4.2
4.0
3.8
3.6
3.4
3.2
I
= 0mA
LOAD
V
= 3V
IN
I
= 500mA
LOAD
V
= 3.6V
IN
I
= 250mA
LOAD
V
= 3.3V
IN
V
IN
= 3V
IN
V
= 2.7V
V
V
= 3.6V
= 2.7V
IN
IN
V
= 3.3V
IN
1.5x MODE
2x MODE
1.5x MODE
1.5x MODE
2x MODE
2x MODE
5.5
5
3.0
0
50 100 150 200 250 300 350 400 450 500
(mA)
0
50 100 150 200 250 300 350 400 450 500
2.5
3
3.5
4
4.5
I
I
(mA)
V
(V)
IN
LOAD
LOAD
3203 G02
3203 G01
3203 G03
V
vs Supply Voltage
Open-Loop Output Resistance
vs Temperature
OUT
(5V Output Setting)
5.4
5.2
5.0
4.8
4.6
4.4
4.2
4.0
2.5
2.0
1.5
1.0
0.5
0
2x MODE
I
= 0mA
LOAD
V
= 2.7V
IN
OUT
V
= 4.5V
I
= 500mA
LOAD
I
= 250mA
LOAD
1.5x MODE
V
= 3.6V
IN
OUT
V
= 4.5V
1.5x MODE
2x MODE
4.5
5.5
–40
–15
10
35
60
85
2.5
3
3.5
4
5
TEMPERATURE (°C)
V
(V)
IN
3203 G06
3203 G04
Oscillator Frequency
vs Supply Voltage
Short-Circuit Current
vs Supply Voltage
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
1400
1200
1000
800
600
400
200
0
2x MODE
1.5x MODE
1.5x MODE
2x MODE
4.5
5.5
2.5
3
3.5
4
5
4.5
5.5
2.5
3
3.5
4
5
V
(V)
V
(V)
IN
IN
3203 G07
3203 G08
32031fa
4
LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Burst Mode Current Threshold
vs Supply Voltage
No-Load Input Current vs Supply
Voltage (LTC3203/LTC3203-1)
Extra Input Current vs Load
Current (LTC3203/LTC3203-1)
(LTC3203/LTC3203-1)
160
140
120
100
500
450
400
350
300
250
200
150
100
50
100
2x MODE
10
1.5x MODE
2x MODE
I
– 2 • I
IN
LOAD
80
60
1
0.1
1.5x MODE
– 1.5 • I
I
IN
LOAD
1.5x MODE
40
20
0
2x MODE
5
0
0.01
0.01
3
3.5
4.5
2.5
5
5.5
4
2.5
3
4
4.5
5.5
3.5
0.1
1
I
10
(mA)
100
1000
V
IN
(V)
V
IN
(V)
LOAD
3209 G12
3203 G10
3203 G11
Input and Output Ripple
(2x Mode)
Input and Output Ripple
(1.5x Mode)
Load Transient (1.5x Mode)
V
V
OUT
IN
100mV/DIV
V
20mV/DIV
IN
AC-COUPLED
20mV/DIV
AC-COUPLED
AC-COUPLED
V
OUT
V
OUT
20mV/DIV
500mA
I
20mV/DIV
OUT
AC-COUPLED
100mA
AC-COUPLED
3203 G15
3203 G14
3203 G13
V
C
C
= 4V
20µs/DIV
V
C
C
I
= 3.6V
= 2.2µF
= 10µF
500ns/DIV
V
C
C
I
= 4V
500ns/DIV
IN
IN
IN
IN
OUT
IN
IN
= 2.2µF
= 10µF
= 2.2µF
= 10µF
OUT
= 300mA
OUT
1.5x MODE
= 300mA
OUT
2x MODE
OUT
1.5x MODE
V
Set Point vs Supply Voltage
V
vs Load Current
FB
FB
Load Transient (2x Mode)
(LTC3203/LTC3203B)
(LTC3203/LTC3202B)
0.94
0.93
0.92
0.91
0.90
0.89
0.88
0.96
0.94
V
OUT
100mV/DIV
AC-COUPLED
0.92
V
= 4V
IN
1.5x MODE
T
= –40°C
T
T
= 25°C
= 85°C
A
A
0.90
0.88
0.86
0.84
0.82
500mA
V
= 3.6V
IN
I
OUT
A
2x MODE
100mA
3203 G16
V
C
C
= 3.6V
20µs/DIV
IN
IN
= 2.2µF
= 10µF
OUT
2x MODE
2.5
3.5
4
4.5
5
5.5
3
500
0
150
250 300 350 400 450
(mA)
50 100
200
I
V
(V)
IN
LOAD
3203 G17
3203 G18
32031fa
5
LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
U
U
U
PI FU CTIO S
C2+ (Pin 1): Flying Capacitor 2 Positive Terminal (C2).
MODE (Pin 6): Mode Selection Input. The LTC3203/
LTC3203-1/LTC3203B/LTC3203B-1 operates in 1.5x
mode if the MODE pin is greater than VMODEH, which
gives higher charge pump efficiency. If the MODE pin is
less than VMODEL, the LTC3203/LTC3203-1/LTC3203B/
LTC3203B-1 operates in 2x mode, which gives a higher
charge pump boost voltage.
VOUT (Pin 2): Regulated Output Voltage. VOUT should be
bypassedwithalowESRceramiccapacitorasclosetothe
pinaspossibleforbestperformance.Thecapacitorshould
have greater than 4.7µF capacitance under all conditions.
C1+ (Pin 3): Flying Capacitor 1 Positive Terminal (C1).
SHDN(Pin4):ActiveLowShutdownInput. AlowonSHDN
puts the LTC3203/LTC3203-1/LTC3203B/LTC3203B-1 in
low current shutdown mode. Do not float the SHDN pin.
VIN (Pin 7): Input Supply Voltage. VIN should be bypassed
withamorethan2.2µFlowESRceramiccapacitortoGND.
C2– (Pin 8): Flying Capacitor 2 Negative Terminal (C2).
VSEL (Pin 5) (LTC3203-1/LTC3203B-1): Output Voltage
Selection Input. A logic 0 at VSEL sets the regulated VOUT
to 4.5V; and a logic 1 sets the regulated VOUT to 5V. Do not
float the VSEL pin.
GND (Pin 9): Ground. This pin should be connected
directly to a low impedance ground plane.
C1– (Pin 10): Flying Capacitor 1 Negative Terminal (C1).
FB (Pin 5) (LTC3203/LTC3203B): Feedback. The voltage
on this pin is compared to the internal reference voltage
(0.91V) by the error amplifier to keep the output in
regulation. An external resistor divider is required
between VOUT and FB to program the output voltage.
Exposed Pad (Pin 11): Ground. This pin must be sol-
dered to the PCB for electrical contact and rated thermal
performance.
32031fa
6
LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
S W
BLOCK DIAGRA
LTC3203/LTC3203B
LTC3203-1/LTC3203B-1
+
–
+
0.91V
0.91V
2x/1.5x
2x/1.5x
6
5
6
4
–
MODE
MODE
SHDN
V
SEL
SOFT-START AND
SHUTDOWN
SOFT-START AND
SHUTDOWN
CONTROL
0.91V
0.82V
4
SHDN
5
2
FB
V
CONTROL
OUT
V
OUT
2
+
–
0.91V
+
OSCILLATOR
+
SWITCH CONTROL
OSCILLATOR
+
SWITCH CONTROL
–
+
C1
+
3
3
C1
S
S
V
7
V
IN
IN
7
–
10 C1
–
10 C1
+
–
1
8
+
–
C2
C2
1
C2
C2
S
S
8
9, 11
GND
9, 11
GND
3203 F02
3203 F01
32031fa
7
LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
U
OPERATIO
The LTC3203/LTC3203-1/LTC3203B/LTC3203B-1 use
a switched capacitor charge pump to boost VIN to a
regulated output voltage. Regulation is achieved by sens-
ing the output voltage through a resistor divider and
modulating the charge pump output current based on the
error signal. A two-phase non-overlapping clock activates
thechargepumpswitches.Thetypicalfrequencyofcharg-
ing and discharging the flying capacitors is 1MHz
(2x mode) or 0.9MHz (1.5x mode). A unique architecture
maintains relatively constant input current for the lowest
possible input noise.
pin the MODE input allows the user to accurately program
the VIN threshold at which the charge pump will switch
from 1.5x mode to 2x mode when VIN starts to fall and
vice versa. Hysteresis on the MODE pin prevents the
LTC3203/LTC3203-1/LTC3203B/LTC3203B-1 from
switching continuously between the two modes.
Output Voltage Programming
The LTC3203-1/LTC3203B-1 has a VSEL input pin that
allows the user to program the regulated output voltage to
either 4.5V or 5V. 4.5V VOUT is useful for driving white
LEDs while a regulated VOUT of 5V is useful for powering
logic circuits.
Mode of Operation
TheLTC3203/LTC3203-1/LTC3203B/LTC3203B-1charge
pump can operate in two modes of voltage conversion:
1.5x or 2x.
The LTC3203/LTC3203B has a FB pin in place of the VSEL
pinthatallowstheoutputvoltagetobeprogrammedusing
an external resistive divider.
Inthe1.5xmodetheflyingcapacitorsarechargedinseries
during the first clock phase, and stacked in parallel on top
of VIN on the second clock phase. Alternatively, in the 2x
mode the flying capacitors are charged on alternate clock
phases from VIN. While one capacitor is being charged
from VIN, the other is stacked on top of VIN and connected
to the output. The two flying capacitors operate out of
phase to minimize both input and output ripple. At light
load the LTC3203/LTC3203-1 go into Burst Mode opera-
tion to reduce quiescent current.
Shutdown Mode
When SHDN is asserted low, the LTC3203/LTC3203-1/
LTC3203B/LTC3203B-1entershutdownmode.Thecharge
pump is first disabled, but the LTC3203/LTC3203-1/
LTC3203B/LTC3203B-1 continue to draw 5µA of supply
current. This current will drop to less than 1µA when VOUT
is fully discharged to 0V. Furthermore, VOUT is discon-
nected from VIN. Since the SHDN pin is a high impedance
CMOS input, it should never be allowed to float.
The conversion mode should be chosen based on consid-
erations of efficiency, available output current and VOUT
ripple. With a given VIN, the 1.5x mode gives a higher
efficiency but lower available output current. The 2x mode
gives a higher available output current but lower effi-
ciency. Moreover, the output voltage ripple in the 2x mode
is lower due to the out-of-phase operation of the two
flying capacitors.
Burst Mode Operation
The LTC3203/LTC3203-1 provide automatic Burst Mode
operation to reduce quiescent current of the power con-
verteratlightloads. BurstModeoperationisinitiatedifthe
output load current falls below an internally programmed
threshold. Once Burst Mode operation is initiated, the part
shuts down the internal oscillator to reduce the switching
losses and goes into a low current state. This state is
referred to as the Sleep state in which the chip consumes
only about 120µA from the input.
Generally, at low VIN, the 2x mode should be selected, and
at higher VIN, the 1.5x mode should be selected. By
connecting a resistive divider from VIN to the MODE input
32031fa
8
LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
U
OPERATIO
When the output voltage drops enough to overcome the
burst comparator hysteresis, the part wakes up and com-
mences normal fixed frequency operation. The output
capacitor recharges and causes the part to re-enter the
Sleep state if the output load still remains less than the
Burst Mode threshold. This Burst Mode threshold varies
with VIN, VOUT and the choice of output storage capacitor.
thermal shutdown circuitry will shut down the charge
pump once the junction temperature exceeds approxi-
mately 150°C. It will enable the charge pump once the
junction temperature drops back to approximately 135°C.
The LTC3203/LTC3203-1/LTC3203B/LTC3203B-1 will
cycle in and out of thermal shutdown indefinitely without
latch-up or damage until the short circuit condition on
V
OUT is removed.
Short-Circuit/Thermal Protection
Soft-Start
The LTC3203/LTC3203-1/LTC3203B/LTC3203B-1 have
built-inshort-circuitcurrentlimitaswellasover-tempera-
ture protection. During a short-circuit condition, the chip
willautomaticallylimittheoutputcurrenttoapproximately
1A. At higher temperatures, or if the input voltage is high
enough to cause excessive self-heating of the part, the
To prevent excessive current flow at VIN during start-up,
the LTC3203/LTC3203-1/LTC3203B/LTC3203B-1 have
built-in soft-start circuitry. Soft-start is achieved by in-
creasing the amount of current available to the output
charge storage capacitor linearly over a period of approxi-
mately 250µs.
32031fa
9
LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
W U U
U
APPLICATIO S I FOR ATIO
2
Power Efficiency
V
OUT
LTC3203/
LTC3203B
C
FB
R1
R2
The power efficiency (η) of the LTC3203/LTC3203-1/
LTC3203B/LTC3203B-1 in 1.5x mode 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 1.5x fractional charge pump is approxi-
mately 1.5 times the load current. In an ideal regulating
1.5x charge pump the power efficiency would be given by:
5
C
FB
OUT
9, 11
3203 F01
GND
Figure 1. Programming the LTC3203/LTC3203B Output Voltage
The voltage divider ratio is given by the expression:
POUT
VOUT • IOUT
VOUT
VOUT
R2 0.91V
η1.5XIdeal
=
=
=
R1
R1
R2
⎛
⎞
⎠
=
−1 or VOUT
=
+ 1 •0.91V
P
V • 1.5IOUT 1.5V
⎜
⎝
⎟
IN
IN IN
Similarly, in 2x mode, the efficiency is similar to that of a
linear regulator with an effective input voltage of twice the
actual input voltage. In an ideal regulating voltage doubler
the power efficiency would be given by:
Typical values for total voltage divider resistance can
range from several kΩs up to 1MΩ. The compensation
capacitor (CFB) is necessary to counteract the pole caused
by the large valued resistors R1 and R2, and the input
capacitance of the FB pin. For best results, CFB should be
5pF for all R1 or R2 greater than 10k and can be omitted
if both R1 and R2 are less than 10k.
POUT VOUT • IOUT VOUT
η2XIdeal
=
=
=
P
V • 2IOUT
2V
IN
IN
IN
TheLTC3203/LTC3203Bcanalsobeconfiguredtocontrol
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 2. 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.
At moderate to high output power the switching losses
and quiescent current of the LTC3203/LTC3203-1/
LTC3203B/LTC3203B-1 are negligible and the expression
above is valid.
As evident from the above two equations, with the same
VIN, the 1.5x mode will give higher efficiency than the
2x mode.
V
R
FB
I
=
LED
Programming the LTC3203/LTC3203B Output Voltage
(FB Pin)
X
2
5
V
OUT
LTC3203/
LTC3203B
While the LTC3203-1/LTC3203B-1 have internal resistive
dividerstoprogramtheoutputvoltage, theprogrammable
LTC3203/LTC3203B may be set to an arbitrary voltage via
an external resistive divider. Since it operates as a voltage
• • •
FB
GND
R
R
X
C
X
OUT
9, 11
doubling charge pump when MODE is less than VMODEL
,
3203 F02
it is not possible to achieve output voltages greater than
twice the available input voltage in this case. Similarly,
whenMODEisgreaterthanVMODEH, theachievableoutput
voltage is less than 1.5 times the available input voltage.
Figure 1 shows the required voltage divider connection.
Figure 2. Programming the LTC3203/LTC3203B Output Current
In this configuration the feedback factor (∆VOUT/∆IOUT
will be very near unity since the small signal LED imped-
ance will be considerably less than the current setting
)
32031fa
10
LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
W U U
APPLICATIO S I FOR ATIO
U
resistor RX. Thus, this configuration will have the highest
loop gain giving it the lowest closed-loop output resis-
tance. Likewise it will also require the largest amount of
output capacitance to preserve stability.
Programming the MODE Pin
By connecting a resistor divider to the MODE pin, the VIN
voltage at which the chip switches modes can be accu-
rately programmed.
Effective Open Loop Output Resistance (ROL)
When VIN ramps up, the voltage at the MODE pin crosses
VMODEH andthechipswitchesfrom2xmodeto1.5xmode.
When VIN starts to drop, the voltage at the MODE pin
crosses VMODEL and the chip switches back to 2x mode.
The MODE pin resistor ratio must be selected such that at
the switch point the output is still able to maintain regula-
The effective open loop output resistance (ROL) of a
charge pump is a very important parameter, which deter-
minesitsstrength.Thevalueofthisparameterdependson
many factors such as the oscillator frequency (fOSC), the
value of the flying capacitor (CFLY), the non-overlap time,
the internal switch resistances (RS), and the ESR of the
external capacitors.
tion at maximum IOUT
:
1.5 • VIN(1.5x) – VOUT > IOUT • ROL(1.5X)
The minimum VIN operating in 1.5x mode occurs at the
switch point where:
Maximum Available Output Current
Figure 3 shows how the LTC3203/LTC3203-1/LTC3203B/
LTC3203B-1 can be modeled as a Thevenin-equivalent
circuit.
⎛
⎞
RMODE1
V = VMODEL
•
+ 1
IN
⎜
⎟
R
⎝
⎠
MODE2
Thus the maximum available output current and voltage
can be calculated from the effective open-loop output
resistance, ROL, and the effective output voltage, 1.5VIN
(in 1.5x mode) or 2VIN (in 2x mode). From Figure 3, the
available current is given by:
therefore:
⎛
⎞
RMODE1
1.5• VMODEL
•
+ 1
⎜
⎟
R
⎝
⎠
MODE2
1.5V − VOUT
IN
> ROL(1.5X)(MAX) •IOUT(MAX) + VOUT(MIN)
IOUT
=
=
In 1.5x mode
ROL
VOUT(MIN) + ROL(1.5x)(MAX) •IOUT(MAX)
RMODE1
>
–1
2V − VOUT
IN
RMODE2
1.5• VMODEL
IOUT
In 2x mode
ROL
As evident from the above two equations, with the same
VIN and ROL, the 2x mode will give more output current
than the 1.5x mode.
7
V
IN
LTC3203/
LTC3203B
MODE
R
R
MODE1
6
C
IN
MODE2
9, 11
R
OL
GND
3203 F04
+
1.5V
IN
OR
2V
+
V
OUT
–
–
Figure 4
IN
3203 F03
Figure 3. Charge Pump Open-Loop Thevenin-Equivalent Circuit
32031fa
11
LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
U
W
U U
APPLICATIO S I FOR ATIO
the LTC3203/LTC3203-1/LTC3203B/LTC3203B-1 use 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 capaci-
tor to maintain at least 4.7µF of capacitance over all
conditions. Note that the actual capacitance of ceramic
capacitors usually drops when biased with DC voltage.
Different capacitor types drop to different extents. Make
sure that the selected ceramic capacitors have enough
capacitance when biased with the required DC voltage.
Fortheexamplegiven,a5Voutputsettingwith±4%output
tolerance and maximum load current of 500mA, a resistor
ratio of:
RMODE1
> 4
RMODE2
at the MODE pin allows the chip to switch modes while
maintaining regulation.
VIN, VOUT Capacitor Selection
The style and value of capacitors used with the
LTC3203/LTC3203-1/LTC3203B/LTC3203B-1determine
several important parameters such as regulator control Likewise, excessive ESR on the output capacitor will tend
loop stability, output ripple, charge pump strength and to degrade the loop stability of the LTC3203/LTC3203-1/
minimum start-up time.
LTC3203B/LTC3203B-1. The closed-loop output resis-
tance of the LTC3203/LTC3203-1/LTC3203B/LTC3203B-
1 are designed to be 0.27Ω (at 1.5x mode). For a 100mA
load current change, the output voltage will change by
about 27mV. If the output capacitor has 0.27Ω or more of
ESR, the closed-loop frequency response will cease to
roll-off in a simple one-pole fashion and poor load tran-
sient response or instability could result. Multilayer ce-
ramic chip capacitors typically have exceptional ESR per-
formanceand, combinedwithagoodboardlayout, should
yield very good stability and load transient performance.
As the value of COUT controls the amount of output ripple,
thevalueofCIN controlstheamountofripplepresentatthe
input pin (VIN). The input current to the LTC3203/
LTC3203-1/LTC3203B/LTC3203B-1willberelativelycon-
stantwhilethechargepumpisoneithertheinputcharging
phase or the output charging phase but will drop to zero
duringtheclocknon-overlaptimes. Sincethenon-overlap
time is small (~40ns) these missing “notches” will result
inonlyasmallperturbationontheinputpowersupplyline.
Note that a higher ESR capacitor such as tantalum
will have higher input noise by the amount of the input
current change times the ESR. Therefore ceramic
capacitors are again recommended for their exceptional
ESR performance. Further input noise reduction can be
achievedbypoweringtheLTC3203/LTC3203-1/LTC3203B/
LTC3203B-1 through a very small series inductor as
shown in Figure 5.
To reduce noise and ripple, it is recommended that low
equivalent series resistance (ESR) multilayer ceramic chip
capacitors (MLCCs) be used for both CIN and COUT. Tanta-
lum and aluminum capacitors are not recommended be-
cause of their high ESR.
In 1.5x mode, the value of COUT directly controls the
amountofoutputrippleforagivenloadcurrent.Increasing
the size of COUT will reduce the output ripple at the expense
of higher minimum turn-on time and higher start-up cur-
rent. Thepeak-to-peakoutputripplefor1.5xmodeisgiven
by the expression:
IOUT
3fOSC • COUT
VRIPPLE(P−P)
=
where fOSC is the LTC3203/LTC3203-1/LTC3203B/
LTC3203B-1’s oscillator frequency (typically 0.9MHz) and
C
OUT is the output charge storage capacitor.
In 2x mode, the output ripple is very low due to the out-of-
phase operation of the two flying capacitors. VOUT remains
almostflatwheneitheroftheflyingcapacitorsisconnected
to VOUT
.
Both the type and value of the output capacitor can signifi-
cantly affect the stability of the LTC3203/LTC3203-1/
LTC3203B/LTC3203B-1. As shown in the Block Diagram,
32031fa
12
LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
U
W
U U
APPLICATIO S I FOR ATIO
10nH
7
V
IN
V
IN
LTC3203*
0.1µF
2.2µF
9, 11
GND
3203 F05
Figure 5. 10nH Inductor Used for Input Noise Reduction
A 10nH inductor will reject the fast current notches,
or more of their capacitance when the rated voltage is
applied. Therefore, when comparing different capacitors,
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 4.7µF,
10V, Y5V ceramic capacitor in a 0805 case may not
provide any more capacitance than a 1µF, 10V, X5R or
X7R capacitor available in the same 0805 case. In fact,
overbiasandtemperaturerangethe1µF, 10V, X5RorX7R
will provide more capacitance than the 4.7µF, 10V, Y5V
capacitor.Thecapacitormanufacturer’sdatasheetshould
be consulted to determine what value of capacitor is
needed to ensure minimum capacitance values are met
over operating temperature and bias voltage.
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.
Flying Capacitor Selection
Warning: Polarized capacitors such as tantalum or
aluminum should never be used for the flying capacitors
since their voltage can reverse upon start-up of the
LTC3203/LTC3203-1/LTC3203B/LTC3203B-1. Low ESR
ceramic capacitors should always be used for the flying
capacitors.
The flying capacitors control the strength of the charge
pump. In order to achieve the rated output current, it is
necessary to have at least 2.2µF of capacitance for each of
the flying capacitors.
Below is a list of ceramic capacitor manufacturers and
how to contact them:
AVX
www.avxcorp.com
www.kemet.com
Ceramic capacitors of different materials lose their ca-
pacitance with higher temperature and voltage at different
rates. For example, a capacitor made of X7R material will
retainmostofitscapacitancefrom–40°Cto85°Cwhereas
Z5U or Y5V style capacitors will lose considerable capaci-
tance over that range. Z5U and Y5V capacitors may also
have a poor voltage coefficient causing them to lose 60%
Kemet
Murata
Taiyo Yuden
Vishay
TDK
www.murata.com
www.t-yuden.com
www.vishay.com
www.component.tdk.com
32031fa
13
LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
U
W
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APPLICATIO S I FOR ATIO
Thermal Management
iftheflyingcapacitorsarenotclosetothepart(i.e.theloop
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 LTC3203/LTC3203-1/
LTC3203B/LTC3203B-1pins.ForahighqualityACground
it should be returned to a solid ground plane that extends
all the way to the LTC3203/LTC3203-1/LTC3203B/
LTC3203B-1. To prevent degraded performance, the FB
trace should be kept away or be shielded from the flying
capacitor traces.
For higher input voltages and maximum output current,
therecanbesubstantialpowerdissipationintheLTC3203/
LTC3203-1/LTC3203B/LTC3203B-1. If the junction tem-
perature increases above approximately 150°C, the ther-
mal shutdown circuitry will automatically deactivate the
output. To reduce the maximum junction temperature, a
goodthermalconnectiontothePCboardisrecommended.
Connecting GND (Pin 9) and the exposed pad (Pin 11) of
theDFNpackagetoagroundplaneunderthedeviceontwo
layers of the PC board can reduce the thermal resistance
of the package and PC board considerably.
GROUND PLANE
C1
Layout Considerations
C
OUT
Due to the high switching frequency and high transient
currents produced by the LTC3203/LTC3203-1/
LTC3203B/LTC3203B-1, careful board layout is neces-
sary for optimum performance. A true ground plane and
short connections to all the external capacitors will
improve performance and ensure proper regulation
under all conditions.
C2
1
2
3
4
5
10
9
11
8
7
6
C
IN
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
3206 F07
LTC3203/LTC3203B COMPONENTS NOT USED
IN LTC3203-1 OR LTC3203B-1
Figure 6. Recommended Layouts
32031fa
14
LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
U
PACKAGE DESCRIPTIO
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699)
R = 0.115
TYP
6
0.38 ± 0.10
10
0.675 ±0.05
3.50 ±0.05
2.15 ±0.05 (2 SIDES)
1.65 ±0.05
3.00 ±0.10
(4 SIDES)
1.65 ± 0.10
(2 SIDES)
PIN 1
TOP MARK
(SEE NOTE 6)
PACKAGE
OUTLINE
(DD) DFN 1103
5
1
0.25 ± 0.05
0.50 BSC
0.75 ±0.05
0.200 REF
0.25 ± 0.05
0.50
BSC
2.38 ±0.10
(2 SIDES)
2.38 ±0.05
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).
CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT
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 THE
TOP AND BOTTOM OF PACKAGE
32031fa
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-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
15
LTC3203/LTC3203-1
LTC3203B/LTC3203B-1
U
TYPICAL APPLICATIO
7
2
5
V
V
OUT
IN
3
10
1
2.2µF
+
–
+
–
C1
C1
C2
C2
LTC3203/
LTC3203B
10µF
332k
100k
FB
8
6
MODE
SHDN
4
47Ω
47Ω
47Ω
47Ω
47Ω
47Ω
GND
ON OFF
9, 11
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LT/LWI 1006 REV A • PRINTED IN USA
LinearTechnology Corporation
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16
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