LINER LTC3204-3.3 Low noise regulated charge pump in 2 2 dfn Datasheet

LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
Low Noise Regulated
Charge Pump in 2 × 2 DFN
FEATURES
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DESCRIPTIO
Fixed 3.3V or 5V Outputs
VIN Range:
1.8V to 4.5V (LTC3204-3.3/LTC3204B-3.3)
2.7V to 5.5V (LTC3204-5/LTC3204B-5)
Output Current:
Up to 150mA (LTC3204-5/LTC3204B-5)
Up to 50mA (LTC3204-3.3/LTC3204B-3.3)
Automatic Burst Mode® Operation with IQ = 48µA
(LTC3204-3.3/LTC3204-5)
Constant Frequency Operation at All Loads
(LTC3204B-3.3/LTC3204B-5)
Low Noise Constant Frequency (1.2MHz) Operation*
Built-In Soft-Start Reduces Inrush Current
Shutdown Disconnects Load from Input
Shutdown Current <1µA
Short-Circuit/Thermal Protection
Available in Low Profile 6-Lead DFN Package
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APPLICATIO S
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2 AA Cell to 3.3V
Li-Ion to 5V
USB On-The-Go Devices
White LED Drivers
Handheld Devices
The LTC®3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
are low noise, constant frequency (1.2MHz) switched capacitor voltage doublers. The LTC3204-3.3/LTC3204B-3.3
can produce a regulated output voltage of 3.3V
from a minimum input voltage of 1.8V (2 alkaline cells)
whereas the LTC3204-5/LTC3204B-5 can produce 5V from
a minimum of 2.7V (Li-Ion battery) input.
LTC3204-3.3/LTC3204-5 feature automatic Burst Mode®
operation at light loads to maintain low supply current
whereas LTC3204B-3.3/LTC3204B-5 feature constant
frequency operation at any load. Built-in soft-start circuitry
prevents excessive inrush current during start-up. Thermal
shutdown and current-limit circuitry allow the parts to
survive a continuous short-circuit from VOUT to GND.
High switching frequency minimizes overall solution
footprint by allowing the use of tiny ceramic capacitors. In shutdown, the load is disconnected from the
input and the quiescent current is reduced to <1µA. The
LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5 are
available in a low profile (0.75mm) 6-lead 2mm × 2mm
DFN package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Burst Mode is a registered trademark of Linear Technology Corporation.
*Protected by U.S. Patents including 6411531.
TYPICAL APPLICATIO
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Output Ripple vs Load Current
30
OUTPUT CAPACITANCE = 2.2µF
VIN = 3.6V
2.2µF
2.7V TO 5.5V
2
2.2µF
1, 7
OFF ON
6
5
C–
VIN
4
C+
3
VOUT
LTC3204-5/
LTC3204B-5
5V
2.2µF
GND
SHDN
3204 TA01a
OUTPUT RIPPLE (mVp-p)
25
20
LTC3204-5
15
10
LTC3204B-5
5
0
0
25
50
75
100
125
OUTPUT CURRENT (mA)
150
3204 TA01b
3204fa
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LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
AXI U RATI GS
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ABSOLUTE
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PACKAGE/ORDER I FOR ATIO
(Note 1)
VIN to GND ................................................... –0.3V to 6V
VOUT to GND ............................................. –0.3V to 5.5V
SHDN to GND............................................... –0.3V to 6V
VOUT Short-Circuit Duration ............................. Indefinite
Operating Temperature Range (Note 2) ...–40°C to 85°C
Storage Temperature Range.................. –65°C to 125°C
Maximum Junction Temperature .......................... 125°C
ORDER PART
NUMBER
LTC3204EDC-3.3
LTC3204EDC-5
LTC3204BEDC-3.3
LTC3204BEDC-5
DC PART
MARKING
LBJV
LBNK
LBVF
LBVG
TOP VIEW
GND 1
VIN 2
6 SHDN
7
VOUT 3
5 C–
4 C+
DC PACKAGE
6-LEAD (2mm × 2mm) PLASTIC DFN
TJMAX = 125°C, θJA = 80°C/W
EXPOSED PAD IS GND (PIN 7)
MUST BE SOLDERED TO PCB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range. Specifications are at TA = 25°C, VIN = 2.4V (LTC3204-3.3/LTC3204B-3.3) or 3.6V (LTC3204-5/LTC3204B-5),
SHDN = VIN, CFLY = 2.2µF, CIN = 2.2µF, COUT = 2.2µF unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
VIN
Input Voltage Range
VOUT
Output Voltage Range
(LTC3204-3.3/LTC3204B-3.3)
(LTC3204-5/LTC3204B-5)
1.8V < VIN < 4.5V, IOUT < 40mA
1.9V < VIN < 4.5V, IOUT < 50mA (LTC3204-3.3/LTC3204B-3.3)
2.7V < VIN < 5.5V, IOUT < 65mA
3.1V < VIN < 5.5V, IOUT < 150mA (LTC3204-5/LTC3204B-5)
IOUT = 0 (LTC3204-3.3)
IOUT = 0 (LTC3204-5)
IOUT = 0 (LTC3204B-3.3)
IOUT = 0 (LTC3204B-5)
SHDN = 0V, VOUT = 0V
(LTC3204-3.3)
(LTC3204-5)
IOUT = 100mA
VIN = 3V, IOUT = 100mA (LTC3204-5/LTC3204B-5)
IIN
No Load Input Current
ISHDN
IBURST
Shutdown Current
Burst Mode Threshold
VR
η
fOSC
VIH
VIL
IIH
IIL
ROL
Output Ripple
Efficiency
Switching Frequency
SHDN Input Threshold
SHDN Input Threshold
SHDN Input Current
SHDN Input Current
Effective Open-Loop Output
Resistance (Note 3)
Output Current Limit
Soft-Start Time
ILIM
TSS
MIN
●
●
1.8
2.7
●
3.168
●
4.8
TYP
●
0.6
1.3
V
V
3.3
3.432
V
5
48
60
1.25
3.6
5.2
15
20
20
82
1.2
Note 1: Absolute Maximum Ratings are those beyond which the life of a
device may be impaired.
Note 2: The LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5 are
guaranteed to meet performance specifications from 0°C to 70°C.
●
1.8
0.4
1
1
●
●
UNITS
4.5
5.5
1
●
SHDN = 0V
VIN = 1.8V, VOUT = 3V (LTC3204-3.3/LTC3204B-3.3)
VIN = 2.7V, VOUT = 4.5V (LTC3204-5/LTC3204B-5)
VOUT = OV
From the Rising Edge of SHDN to 90% of VOUT
MAX
–1
–1
7
6
300
0.75
V
µA
µA
mA
mA
µA
mA
mA
mVP-P
%
MHz
V
V
µA
µA
Ω
Ω
mA
ms
Specifications over the –40°C to 85°C operating temperature range are
assured by design, characterization and correlation with statistical process
controls.
Note 3: ROL ≡ (2VIN – VOUT)/IOUT
3204fa
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LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
TYPICAL PERFOR A CE CHARACTERISTICS
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(TA = 25°C, CFLY = CIN = COUT = 2.2µF unless otherwise specified)
Oscillator Frequency vs
Temperature
1.4
1.25
1.3
1.00
0.75
0.50
0.25
0.9
VIN = 4.5V
1.2
VIN = 2.4V
1.1
VIN = 1.8V
1.0
1.5
2.0
2.5
3.0
3.5
SUPPLY VOLTAGE (V)
4.0
0.8
–50
4.5
–20
10
40
70
TEMPERATURE (°C)
100
3204 G01
0.7
HIGH-TO-LOW THRESHOLD
0.6
SHDN THRESHOLD HI-TO-LO (V)
VIN = 3.2V
0.7
VIN = 2.4V
VIN = 1.8V
0.6
0
50
100
150
TEMPERATURE (°C)
VIN = 3.2V
0.7
VIN = 2.4V
0.6
VIN = 1.8V
0.5
0.4
–50
4.0
4.5
Short-Circuit Current vs Supply
0
50
100
150
TEMPERATURE (°C)
3204 G04
2.5
3.0
3.5
SUPPLY VOLTAGE (V)
350
0.8
0.8
2.0
3204 G03
SHDN HI-to-LO Threshold vs
Temperature
0.9
0.5
–50
0.5
1.5
130
3204 G02
SHDN LO-to-HI Threshold vs
Temperature
SHDN THRESHOLD LO-TO-HI (V)
LOW-TO-HIGH THRESHOLD
0.8
0.9
SHORT-CIRCUIT CURRENT (mA)
0
SHDN Threshold Voltage vs
Supply Voltage
THRESHOLD VOLTAGE (V)
1.50
FREQUENCY (MHz)
FREQUENCY (MHz)
Oscillator Frequency vs
Supply Voltage
3204 G05
300
250
200
DEVICE CYCLES
IN AND OUT OF
THERMAL SHUTDOWN
150
100
50
0
1.5
2.0
2.5
3.0
3.5
SUPPLY VOLTAGE (V)
4.0
4.5
3204 G06
3204fa
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LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
TYPICAL PERFOR A CE CHARACTERISTICS
U W
(TA = 25°C, CFLY = CIN = COUT = 2.2µF unless otherwise specified)
Output Load Capability at 4%
Below Regulation
Load Regulation
400
3.35
LOAD CURRENT (mA)
3.25
VIN = 3.2V
VIN = 1.8V
3.15
3.10
3.05
100
200
300
400
LOAD CURRENT (mA)
TA = 25°C
300
250
TA = –45°C
200
6
100
0
1.5
500
2.5
3.0
2.0
SUPPLY VOLTAGE (V)
1.8
60
1.6
LTC3204B-3.3
1.4
56
1.2
54
1.0
52
0.8
0.6
LTC3204-3.3
0.4
46
10
Efficiency vs Supply Voltage
100
VIN = 2.4V
90
80
1
LTC3204-3.3
(BURST MODE
OPERATION)
0.1
2
2.2 2.4 2.6
2.8
SUPPLY VOLTAGE (V)
3
3.2
0.1
1
10
100
LOAD CURRENT (mA)
VOUT Soft-Start Response
IOUT = 1mA
40
30
1.8
2.0
2.2 2.4 2.6
2.8
SUPPLY VOLTAGE (V)
VOUT
20mV/DIV
(AC COUPLED)
VIN = 2.4V
ILOAD = 50mA
500ns/DIV
3204 G14
3204 G14
50mA
30mA
10µs/DIV
VIN = 2.4V
IOUT = 30mA TO 50mA STEP
32043204
G15 G15
3204fa
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3.2
3204 G12
IOUT
3204 G13
3204 G13
3.0
Load Transient Response
SHDN
2V/DIV
500µs/DIV
50
0
1000
Output Ripple
VOUT
20mV/DIV
(AC COUPLED)
VIN = 2.4V
ILOAD = 50mA
IOUT = 30mA
3204 G11
3204 G10
VOUT
2V/DIV
60
10
0.01
0.01
0
THEORETICAL MAX
70
20
0.2
1.8
100
3204 G09
LTC3204B-3.3
(NON-BURST MODE
OPERATION)
EXCESS INPUT CURRENT (mA)
NO-LOAD INPUT CURRENT (µA)
62
50
0
TEMPERATURE (°C)
3204 G08
NO-LOAD INPUT CURRENT (mA)
2.0
44
5
–50
3.5
Extra Input Current vs Load Current
(IIN-2ILOAD)
64
48
7
150
No-Load Input Current vs
Supply Voltage
50
8
TA = 90°C
3204 G07
58
VIN = 1.8V
VOUT = 3V
50
VIN = 2.4V
0
9
EFFICIENCY (%)
OUTPUT VOLTAGE (V)
3.30
Effective Open-Loop Output
Resistance vs Temperature
VOUT = 3.168V
350
3.20
(LTC3204-3.3/LTC3204B-3.3 ONLY)
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
TYPICAL PERFOR A CE CHARACTERISTICS
U W
(LTC3204-5/LTC3204B-5 ONLY)
(TA = 25°C, CFLY = CIN = COUT = 2.2µF unless otherwise specified)
5.20
500
450
VIN = 4.2V
VIN = 3.6V
4.80
VIN = 2.7V
4.70
TA = 90°C
300
250
200
150
5
50
200
400
300
LOAD CURRENT (mA)
0
2.7
500
3.0
3.3
3.6
3.9
SUPPLY VOLTAGE (V)
2.8
2.4
2.0
LTC3204B-5
58
1.6
56
1.2
54
0.8
52
0.4
2.7
3
3.6
3.9
3.3
SUPPLY VOLTAGE (V)
4.2
0
4.5
EXCESS INPUT CURRENT (mA)
NO-LOAD INPUT CURRENT (µA)
64
62
NO-LOAD INPUT CURRENT (mA)
3.2
50
10
3.6
66
100
Efficiency vs Supply Voltage
100
VIN = 3.6V
1
90
LTC3204B-5
(N0N-BURST MODE
OPERATION)
THEORETICAL MAX
80
LTC3204-5
(BURST-MODE
OPERATION)
0.1
70
60
IOUT = 100mA
IOUT = 10mA
50
IOUT = 1mA
40
30
20
10
0.01
0.01
0.1
1
10
100
LOAD CURRENT (mA)
0
2.7
1000
3.0
3.3
3.6
3.9
SUPPLY VOLTAGE (V)
VOUT Soft-Start
4.2
4.5
3204 G21
3204 G20
3204 G19
Output Ripple
VOUT
2V/DIV
50
3204 G18
Extra Input Current vs Load Current
(IIN-2ILOAD)
LTC3204-5
0
TEMPERATURE (°C)
3204 G17
4.0
60
4
–50
4.2
EFFICIENCY (%)
100
0
No-Load Input Current vs
Supply Voltage
68
6
TA = –45°C
3204 G16
70
VIN = 2.7V
VOUT = 4.5V
7
TA = 25°C
350
100
4.60
4.50
8
VOUT = 4.8V
400
5.00
OUTPUT LOAD (mA)
OUTPUT VOLTAGE (V)
5.10
4.90
Effective Open-Loop Output
Resistance vs Temperature
Output Load Capability at 4%
Below Regulation
Load Regulation
Load Transient Response
VOUT
50mV/DIV
(AC COUPLED)
VOUT
20mV/DIV
(AC COUPLED)
IOUT
 HDN
S
5V/DIV
100mA
60mA
VIN = 3.6V
IOUT = 100mA
500µs/DIV
3204 G22
VIN = 3.6V
IOUT = 100mA
500ns/DIV
3204 G23
10µs/DIV
VIN = 3.6V
IOUT = 60mA TO 100mA STEP
3204 G24
3204fa
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LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
PI FU CTIO S
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GND (Pin 1, 7): Ground. These pins should be tied to a
ground plane for best performance. The exposed pad must
be soldered to PCB ground to provide electrical contact
and optimum thermal performance.
VIN (Pin 2): Input Supply Voltage. VIN should be bypassed
with a 1µF to 4.7µF low ESR ceramic capacitor.
C+ (Pin 4): Flying Capacitor Positive Terminal.
C– (Pin 5): Flying Capacitor Negative Terminal.
 HDN (Pin 6): Active Low Shutdown Input. A low on
S
 H
 D
 N
 disables the LTC3204-3.3/LTC3204-5/LTC3204B-3.3/
S
LTC3204B-5. This pin must not be allowed to float.
VOUT (Pin 3): Regulated Output Voltage. VOUT should be
bypassed with a low ESR ceramic capacitor providing at
least 2µF of capacitance as close to the pin as possible
for best performance.
BLOCK DIAGRA
W
SOFT-START
AND
SWITCH CONTROL
VOUT
6
SHDN
4
C+
5
C–
3
1.2MHz
OSCILLATOR
–
+
CHARGE
PUMP
VIN
2
3204 BD
GND
1, 7
3204fa
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OPERATIO
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
(Refer to the Block Diagram)
The LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
use a switched capacitor charge pump to boost VIN to a
regulated output voltage. Regulation is achieved by sensing
the output voltage through an internal resistor divider and
modulating the charge pump output current based on the
error signal. A 2-phase nonoverlapping clock activates the
charge pump switches. The flying capacitor is charged from
VIN on the first phase of the clock. On the second phase
of the clock it is stacked in series with VIN and connected
to VOUT. This sequence of charging and discharging the
flying capacitor continues at a free running frequency of
1.2MHz (typ).
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 IC consumes only about 40µA
from the input. When the output voltage droops enough
to overcome the burst comparator hysteresis, the part
wakes up and commences normal fixed frequency operation. The output capacitor recharges and causes the part
to reenter 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.
Shutdown Mode
Soft-Start
In shutdown mode, all circuitry is turned off and the
LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
draws only leakage current from the VIN supply. Furthermore, VOUT is disconnected from VIN. The SHDN pin is a
CMOS input with a threshold voltage of approximately 0.7V.
The LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
are in shutdown when a logic low is applied to the SHDN
pin. Since the SHDN pin is a very high impedance CMOS
input, it should never be allowed to float. To ensure that
its state is defined, it must always be driven with a valid
logic level.
The LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
have built-in soft-start circuitry to prevent excessive current
flow during start-up. The soft-start is achieved by charging
an internal capacitor with a very weak current source. The
voltage on this capacitor, in turn, slowly ramps the amount
of current available to the output storage capacitor from
zero to a value of 300mA over a period of approximately
0.75ms. The soft-start circuit is reset in the event of a
commanded shutdown or thermal shutdown.
Since the output voltages of these devices can go above
the input voltage, special circuitry is required to control
the internal logic. Detection logic will draw an input current
of 5µA when the devices are in shutdown. However, this
current will be eliminated if the output voltage (VOUT) is
less than approximately 0.8V.
The LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
have built-in short-circuit current limit as well as over-temperature protection. During a short-circuit condition, they
will automatically limit their output current to approximately
300mA. At higher temperatures, or if the input voltage is
high enough to cause excessive self-heating of the part,
the thermal shutdown circuitry will shutdown the charge
pump once the junction temperature exceeds approximately
160°C. It will enable the charge pump once the junction
temperature drops back to approximately 150°C. The
LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5 will
cycle in and out of thermal shutdown indefinitely without
latchup or damage until the short-circuit condition on
VOUT is removed.
Burst Mode Operation
The LTC3204-3.3/LTC3204-5 provide automatic Burst
Mode operation to reduce supply current at light loads.
Burst Mode operation is initiated if the output load current
falls below an internally programmed threshold. Once
Short-Circuit/Thermal Protection
3204fa
7
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
APPLICATIO S I FOR ATIO
U
U U
The power efficiency (η) of the LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5 is similar to that of a linear
regulator with an effective input voltage of twice the actual
input voltage. This occurs because the input current for a
voltage doubling charge pump is approximately twice the
output current. In an ideal regulating voltage doubler the
power efficiency would be given by:
η=
POUT VOUT • IOUT VOUT
=
=
PIN
VIN • 2IOUT
2VIN
At moderate to high output power, the switching losses
and the quiescent current of the LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5 are negligible and the expression above is valid. For example, with VIN = 3V, IOUT =
100mA and VOUT regulating to 5V, the measured efficiency
is 81.8% which is in close agreement with the theoretical
83.3% calculation.
Maximum Available Output Current
For the LTC3204-3.3/LTC3204-5/LTC3204B-3.3/
LTC3204B-5,the maximum available output current and
voltage can be calculated from the effective open-loop
output resistance, ROL, and the effective input voltage,
2VIN(MIN).
ROL
+
–
2VIN
+
IOUT
VOUT
–
3204 F01
Figure 1. Equivalent Open-Loop Circuit
From Fig. 1, the available current is given by:
IOUT =
2VIN – VOUT
ROL
Effective Open Loop Output Resistance (ROL)
The effective open loop output resistance (ROL) of a charge
pump is a very important parameter which determines the
strength of the charge pump. The value of this parameter
depends on many factors such as the oscillator frequency
8
(fOSC), value of the flying capacitor (CFLY), the nonoverlap
time, the internal switch resistances (RS), and the ESR of
the external capacitors. A first order approximation for
ROL is given below:
ROL ≅ 2∑ RS +
S=1 TO 4
1
f OSC • C FLY
Typical ROL values as a function of temperature are shown
in Figure 2.
EFFECTIVE OPEN-LOOP OUTPUT RESISTANCE (Ω)
W
Power Efficiency
8
VIN = 2.7V
VOUT = 4.5V
7
6
5
4
–50
0
50
100
TEMPERATURE (°C)
3204 F02
Figure 2. Typical ROL vs Temperature
VIN, VOUT Capacitor Selection
The style and value of capacitors used with the LTC3204-3.3/
LTC3204-5/LTC3204B-3.3/LTC3204B-5 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
ESR (<0.1Ω) ceramic capacitors be used for both CIN and
COUT. These capacitors should be 1µF or greater. Tantalum
and aluminum capacitors are not recommended because
of their high ESR.
The value of COUT directly controls the amount of output
ripple for a given load current. Increasing the size of COUT
will reduce the output ripple at the expense of higher
minimum turn-on time. The peak-to-peak output ripple
is approximately given by the expression:
VRIPPLE(P −P) ≅
IOUT
2f OSC • C OUT
3204fa
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
APPLICATIO S I FOR ATIO
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where f OSC is the oscillator frequency (typically
1.2MHz) and COUT is the value of output charge storage
capacitor.
Also, the value and style of the output capacitor can significantly affect the stability of the LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5. As shown in the Block
Diagram, the LTC3204-3.3/LTC3204-5/LTC3204B3.3/LTC3204B-5 use a linear 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 storage capacitor. This output capacitor also serves to form the dominant pole of
the control loop. To prevent ringing or instability on the
LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5,
it is important to maintain at least 1µF of capacitance over
all conditions.
Excessive ESR on the output capacitor can degrade the loop
stability of the LTC3204-3.3/LTC3204-5/LTC3204B-3.3/
LTC3204B-5. The closed loop output resistance of the
LTC3204-5 is designed to be 0.5Ω. For a 100mA load
current change, the output voltage will change by about
50mV. If the output capacitor has 0.5Ω 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. Ceramic capacitors
typically have exceptional ESR performance and combined
with a good board layout should yield very good stability
and load transient performance.
As the value of COUT controls the amount of output ripple,
the value of CIN controls the amount of ripple present at
the input pin (VIN). The input current to the LTC3204-3.3/
LTC3204-5/LTC3204B-3.3/LTC3204B-5 will be relatively
constant during the input charging phase or the output
charging phase but will drop to zero during the 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 voltage drop in the ESR. Therefore, ceramic
capacitors are again recommended for their exceptional
ESR performance.
Further input noise reduction can be achieved by powering
the LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
through a very small series inductor as shown in Figure 3.
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.
1cm OF WIRE
10nH
VIN
0.22µF
2
VIN
LTC3204-3.3/
LTC3204-5
2.2µF
1
GND
32005 F03
Figure 3. 10nH Inductor Used for
Additional Input Noise Reduction
Flying Capacitor Selection
Warning: A polarized capacitor such as tantalum or
aluminum should never be used for the flying capacitor since its voltage can reverse upon start-up of the
LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5.
Low ESR ceramic capacitors should always be used for
the flying capacitor.
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 1µF of capacitance for the flying capacitor.
For very light load applications, the flying capacitor may be
reduced to save space or cost. From the first order approximation of ROL in the section “Effective Open-Loop Output
Resistance,” the theoretical minimum output resistance
of a voltage doubling charge pump can be expressed by
the following equation:
R0L(MIN) =
2VIN – VOUT
1
≅
IOUT
f OSC • C FLY
where fOSC is the switching frequency (1.2MHz) and CFLY
is the value of the flying capacitor. 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.
3204fa
9
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
APPLICATIO S I FOR ATIO
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Ceramic Capacitors
Ceramic capacitors of different materials lose their capacitance with higher temperature and voltage at different rates.
For example, a capacitor made of X5R or X7R material
will retain most of its capacitance from –40°C to 85°C
whereas a Z5U or Y5V style capacitor will lose considerable
capacitance over that range. Z5U and Y5V capacitors may
also have a poor voltage coefficient causing them to lose
60% 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
discussing the specified capacitance value. For example,
over rated voltage and temperature conditions, a 1µF 10V
Y5V ceramic capacitor in a 0603 case may not provide any
more capacitance than a 0.22µF 10V X7R capacitor available in the same 0603 case. In fact, for most LTC3204-3.3/
LTC3204-5/LTC3204B-3.3/LTC3204B-5 applications, these
capacitors can be considered roughly equivalent. The
capacitor manufacturer’s data sheet should be consulted
to ensure the desired capacitance at all temperatures and
voltages.
Below is a list of ceramic capacitor manufacturers and
how to contact them:
AVX
Kemet
Murata
Taiyo Yuden
Vishay
www.avxcorp.com
www.kemet.com
www.murata.com
www.t-yuden.com
www.vishay.com
TDK
www.component.tdk.com
Layout Considerations
Due to the high switching frequency and high transient
currents produced by LTC3204-3.3/LTC3204-5/LTC3204B3.3/LTC3204B-5, careful board layout is necessary 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.
Figure 4 shows an example layout for the LTC3204-3.3/
LTC3204-5/LTC3204B-3.3/LTC3204B-5.
CIN
0603
GND
SHDN
C–
VIN
VOUT
CFLY
0603
COUT
0603
C+
3204 F04
Figure 4. Recommended Layout
Thermal Management
For higher input voltages and maximum output current, there can be substantial power dissipation in the
LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5. If
the junction temperature increases above approximately
160°C, the thermal shutdown circuitry will automatically
deactivate the output. To reduce the maximum junction
temperature, a good thermal connection to the PC board
is recommended. Connecting the GND pin (Pin 1) and
the exposed pad of the DFN package (Pin 7) to a ground
plane under the device on two layers of the PC board
can reduce the thermal resistance of the package and PC
board considerably.
Derating Power at High Temperatures
To prevent an overtemperature condition in high power
applications, Figure 5 should be used to determine the
maximum combination of ambient temperature and power
dissipation.
The power dissipated in the LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5 should always fall under the
line shown for a given ambient temperature. The power
dissipation in the LTC3204-3.3/ LTC3204-5/LTC3204B-3.3/
LTC3204B-5 is given by the expression:
PD = (2VIN – VOUT )• IOUT
This derating curve assumes a maximum thermal resistance, θJA, of 80°C/W for the 2mm × 2mm DFN package.
3204fa
10
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
APPLICATIO S I FOR ATIO
U
W
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This can be achieved from a printed circuit board layout
with a solid ground plane and a good connection to the
ground pins of LTC3204-3.3/LTC3204-5/LTC3204B-3.3/
LTC3204B-5 and the exposed pad of the DFN package.
Operation out of this curve will cause the junction temperature to exceed 160°C which may trigger the thermal
shutdown.
3.0
POWER DISSIPATION (W)
2.5
2.0
1.5
1.0
0.5
0
–50 –25
25 50 75 100 125 150
0
AMBIENT TEMPERATURE (C)
3204 G05
Figure 5. Maximum Power Dissipation
vs Ambient Temperature
PACKAGE DESCRIPTIO
U
DC Package
6-Lead Plastic DFN (2mm × 2mm)
(Reference LTC DWG # 05-08-1703)
R = 0.115
TYP
0.56 ± 0.05
(2 SIDES)
0.675 ±0.05
2.50 ±0.05
1.15 ±0.05 0.61 ±0.05
(2 SIDES)
PIN 1 BAR
PACKAGE
TOP MARK
OUTLINE
(SEE NOTE 6)
0.38 ± 0.05
4
2.00 ±0.10
(4 SIDES)
PIN 1
CHAMFER OF
EXPOSED PAD
3
0.25 ± 0.05
0.50 BSC
1.42 ±0.05
(2 SIDES)
0.200 REF
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
6
0.75 ±0.05
1
(DC6) DFN 1103
0.25 ± 0.05
0.50 BSC
1.37 ±0.05
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WCCD-2)
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
3204fa
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 representation that
the interconnection of its circuits as described herein will not infringe on existing patent rights.
11
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
TYPICAL APPLICATIO S
U
Regulated 3.3V Output
2.2µF
2
VIN
1.8V TO 4.5V
2.2µF
1, 7
6
OFF ON
4
C+
3
VOUT
5
C–
VIN
VOUT
3.3V
2.2µF
LTC3204-3.3/
LTC3204B-3.3
GND
SHDN
3204 TA02
Lithium-Ion Battery to 5V White or Blue LED Driver
2.2µF
5
2
3V TO 4.4V
Li-Ion
BATTERY
ON OFF
2.2µF
C–
VIN
4
C+ 3
VOUT
DRIVE UP TO 5 LEDS
6
SHDN
(APPLY PWM WAVEFORM FOR
ADJUSTABLE BRIGHTNESS CONTROL)
100Ω
2.2µF
LTC3204-5/
LTC3204B-5
GND
100Ω
100Ω
100Ω
100Ω
1, 7
VSHDN
3200-5 TA03
t
USB Port to Regulated 5V Power Supply
2.2µF
5
C–
2
VIN
4
C+
VOUT
3
LTC3204-5
2.2µF
6
SHDN
GND
1, 7
2.2µF
VOUT
5V ±4%
32005 TA05
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1751-3.3/
LTC1751-5
LTC1983-3/
LTC1983-5
LTC3200-5
100mA, 800kHz Regulated Doubler
VIN: 2V to 5V, VOUT(MAX) = 3.3V/5V, IQ = 20µA,
ISD <2µA, MS8 Package
VIN: 3.3V to 5.5V, VOUT(MAX) = –3V/–5V, IQ = 25µA,
ISD <1µA, ThinSOT Package
VIN: 2.7V to 4.5V, VOUT(MAX) = 5V, IQ = 3.5mA,
ISD <1µA, ThinSOT Package
VIN: 2.7V to 4.5V, VOUT(MAX) = 5.5V, IQ = 2.5mA,
ISD <1µA, DFN, MS Packages
LTC3202
100mA, 900kHz Regulated Inverter
100mA, 2MHz Low Noise, Doubler/
White LED Driver
125mA, 1.5MHz Low Noise, Fractional
White LED Driver
3204fa
12 Linear Technology Corporation
LT/LT 0605 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507 ● www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2004
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