LTC3204-3.3/LTC3204-5/
FEATURES
DESCRIPTIO
U
TYPICAL APPLICATIO
U
APPLICATIO S
U
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
OFF ON
V
IN
GND
SHDN
V
OUT
C
–
C
+
LTC3204-5/
LTC3204B-5
2.2µF 2.2µF
2.2µF
5V
2.7V TO 5.5V
3204 TA01a
1, 7
2
3
4
5
6
OUTPUT CURRENT (mA)
0
0
OUTPUT RIPPLE (mVp-p)
5
10
15
20
30
25
50 75 100
3204 TA01b
125 150
25
OUTPUT CAPACITANCE = 2.2µF
VIN = 3.6V
LTC3204B-5
LTC3204-5
LTC3204B-3.3/LTC3204B-5
Low Noise Regulated
Charge Pump in 2 × 2 DFN
■
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
■
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 V
to GND.
OUT
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.
Burst Mode is a registered trademark of Linear Technology Corporation.
*Protected by U.S. Patents including 6411531.
Output Ripple vs Load Current
3204fa
1
LTC3204-3.3/LTC3204-5/
ABSOLUTE AXI U RATI GS
W
W W
U
FOR ATIO
PACKAGE/ORDER
I
U UW
ELECTRICAL CHARACTERISTICS
TOP VIEW
DC PACKAGE
6-LEAD (2mm × 2mm) PLASTIC DFN
4
5
6
7
3
2
1GND
V
IN
V
OUT
SHDN
C
–
C
+
LTC3204B-3.3/LTC3204B-5
(Note 1)
VIN to GND ................................................... –0.3V to 6V
V
to GND .............................................–0.3V to 5.5V
OUT
SHD
N to GND ...............................................– 0.3V to 6V
V
Short-Circuit Duration ............................. Indefinite
OUT
Operating Temperature Range (Note 2) ...–40°C to 85°C
Storage Temperature Range .................. –65°C to 125°C
Maximum Junction Temperature .......................... 125°C
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),
SHDN = VIN, C
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN Input Voltage Range (LTC3204-3.3/LTC3204B-3.3)
(LTC3204-5/LTC3204B-5)
V
Output Voltage Range 1.8V < VIN < 4.5V, I
OUT
1.9V < VIN < 4.5V, I
2.7V < VIN < 5.5V, I
3.1V < VIN < 5.5V, I
IIN No Load Input Current I
I
I
I
I
Shutdown Current
SHD
N
I
Burst Mode Threshold (LTC3204-3.3) 15 mA
BURST
(LTC3204-5) 20 mA
VR Output Ripple I
η Efficiency VIN = 3V, I
f
Switching Frequency
OSC
VIH
VIL
IIH
IIL
ROL Effective Open-Loop Output VIN = 1.8V, V
Resistance (Note 3) VIN = 2.7V, V
I
Output Current Limit V
LIM
TSS Soft-Start Time From the Rising Edge of SHDN to 90% of V
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.
2
= 2.2µF, CIN = 2.2µF, C
FLY
SHD
N Input Threshold
SHD
N Input Threshold
SHD
N Input Current
SHD
N Input Current
= 2.2µF unless otherwise noted.
OUT
= 0 (LTC3204-3.3) 48 µA
OUT
= 0 (LTC3204-5) 60 µA
OUT
= 0 (LTC3204B-3.3) 1.25 mA
OUT
= 0 (LTC3204B-5) 3.6 mA
OUT
SHD
N = 0V, V
= 100mA 20 mV
OUT
SHD
N = 0V
= OV 300 mA
OUT
ORDER PART
NUMBER
LTC3204EDC-3.3
LTC3204EDC-5
LTC3204BEDC-3.3
LTC3204BEDC-5
DC PART
MARKING
LBJV
LBNK
T
= 125°C, θJA = 80°C/W
JMAX
EXPOSED PAD IS GND (PIN 7)
MUST BE SOLDERED TO PCB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
●
1.8 4.5 V
●
2.7 5.5 V
< 40mA
OUT
< 50mA (LTC3204-3.3/LTC3204B-3.3) ● 3.168 3.3
OUT
< 65mA
OUT
< 150mA (LTC3204-5/LTC3204B-5)
OUT
= 0V 1 µA
OUT
= 100mA (LTC3204-5/LTC3204B-5) 82 %
OUT
= 3V (LTC3204-3.3/LTC3204B-3.3) 7 Ω
OUT
= 4.5V (LTC3204-5/LTC3204B-5) 6 Ω
OUT
0.75 ms
OUT
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 ≡ (2V
IN
– V
OUT
●
4.8 5
●
0.6 1.2 1.8 MHz
●
1.3 V
●
0.4 V
●
–1 1 µA
●
–1 1 µA
)/I
OUT
LBVF
LBVG
3.432
5.2
V
V
P-P
3204fa
LTC3204-3.3/LTC3204-5/
TYPICAL PERFOR
U W
CE CHARACTERISTICSA
TEMPERATURE (°C)
–50 150
3204 G05
0
50
100
TEMPERATURE (°C)
–50 150
0
50
100
3204 G04
THRESHOLD VOLTAGE (V)
0.7
0.8
0.6
0.5
0.9
SHDN THRESHOLD LO-TO-HI (V)
0.7
0.8
0.6
0.5
0.9
SHDN THRESHOLD HI-TO-LO (V)
0.6
0.7
0.5
0.4
0.8
SUPPLY VOLTAGE (V)
1.5
FREQUENCY (MHz)
1.50
1.25
1.00
0.75
0.50
0.25
0
2.0 2.5 3.0 3.5 4.0 4.5
3204 G01
SUPPLY VOLTAGE (V)
1.5 2.0 2.5 3.0 3.5 4.0 4.5
3204 G03
TEMPERATURE (°C)
–50
FREQUENCY (MHz)
1.4
1.3
1.2
1.1
1.0
0.9
0.8
–20 10 40 70 100 130
3204 G02
SUPPLY VOLTAGE (V)
SHORT-CIRCUIT CURRENT (mA)
350
300
250
200
150
100
50
0
3204 G06
1.5
2.0
2.5 3.0 3.5 4.0 4.5
DEVICE CYCLES
IN AND OUT OF
THERMAL SHUTDOWN
VIN = 4.5V
HIGH-TO-LOW THRESHOLD
LOW-TO-HIGH THRESHOLD
VIN = 3.2V
VIN = 3.2V
VIN = 1.8V
VIN = 1.8V
VIN = 2.4V
VIN = 1.8V
VIN = 2.4V
VIN = 2.4V
LTC3204B-3.3/LTC3204B-5
(TA = 25°C, C
= CIN = C
FLY
Oscillator Frequency vs
Supply Voltage
SHD
N LO-to-HI Threshold vs
Temperature
= 2.2µF unless otherwise specified)
OUT
Oscillator Frequency vs
Temperature
SHD
Temperature
N HI-to-LO Threshold vs
SHD
N Threshold Voltage vs
Supply Voltage
Short-Circuit Current vs Supply
3204fa
3
LTC3204-3.3/LTC3204-5/
SUPPLY VOLTAGE (V)
1.8
EFFICIENCY (%)
100
90
80
70
60
50
40
30
20
10
0
2.2
2.6
2.8
2.0
2.4
3.0
3.2
TEMPERATURE (°C)
–50
0
50
100
6
7
5
9
3204 G09
VIN = 1.8V
V
OUT
= 3V
3204 G12
3204 G07
SUPPLY VOLTAGE (V)
LOAD CURRENT (mA)
400
350
300
250
200
150
100
50
0
3204 G08
1.5
2.0
2.5 3.0 3.5
8
I
OUT
= 1mA
THEORETICAL MAX
I
OUT
= 30mA
LOAD CURRENT (mA)
0
OUTPUT VOLTAGE (V)
3.35
3.30
3.25
3.20
3.15
3.10
3.05
100 200 300 400 500
VIN = 1.8V
VIN = 2.4V
VIN = 3.2V
V
OUT
= 3.168V
TA = 25°C
TA = 90°C
TA = –45°C
SUPPLY VOLTAGE (V)
1.8
44
NO-LOAD INPUT CURRENT (µA)
NO-LOAD INPUT CURRENT (mA)
46
50
52
54
64
58
2.2
2.6
2.8
3204 G10
48
60
62
56
0
0.2
0.6
0.8
1.0
2.0
1.4
0.4
1.6
1.8
1.2
2
2.4
3
3.2
LTC3204B-3.3
LTC3204-3.3
LOAD CURRENT (mA)
0.01
0.1
EXCESS INPUT CURRENT (mA)
1
0.01 0.1 1 10 100
3204 G11
10
1000
LTC3204B-3.3
(NON-BURST MODE
OPERATION)
LTC3204-3.3
(BURST MODE
OPERATION)
VIN = 2.4V
TYPICAL PERFOR A CE CHARACTERISTICS
U W
LTC3204B-3.3/LTC3204B-5
(TA = 25°C, C
= CIN = C
FLY
= 2.2µF unless otherwise specified)
OUT
(LTC3204-3.3/LTC3204B-3.3 ONLY)
Load Regulation
No-Load Input Current vs
Supply Voltage
V
Soft-Start Response Output Ripple
OUT
Output Load Capability at 4%
Below Regulation
Extra Input Current vs Load Current
(IIN-2I
)
LOAD
Effective Open-Loop Output
Resistance vs Temperature
Efficiency vs Supply Voltage
Load Transient Response
V
OUT
2V/DIV
SHD
N
2V/DIV
VIN = 2.4V
I
LOAD
4
= 50mA
500µs/DIV
3204 G13 3204 G14 3204 G15
V
OUT
20mV/DIV
(AC COUPLED)
VIN = 2.4V
I
= 50mA
LOAD
500ns/DIV
V
20mV/DIV
(AC COUPLED)
50mA
I
OUT
30mA
OUT
VIN = 2.4V
I
= 30mA TO 50mA STEP
OUT
10µs/DIV
3204fa
2.7 4.5
3.0
3.3
3.6 3.9 4.2
3204 G18
3204 G21
3204 G233204 G22
3204 G24
3204 G16
3204 G17
SUPPLY VOLTAGE (V)
2.7
OUTPUT LOAD (mA)
3.93.0 3.3 3.6 4.2
500
450
400
350
300
250
200
150
100
50
0
TEMPERA
TURE (°C)
100
0 50
VIN = 2.7V
V
OUT
= 4.5V
V
OUT
= 4.8V
LOAD CURRENT (mA)
0
5.20
5.10
5.00
4.90
4.80
4.70
4.60
4.50
300
100 200 400 500
OUTPUT VOLTAGE (V)
VIN = 4.2V
VIN = 2.7V
VIN = 3.6V
SUPPLY VOLTAGE (V)
EFFICIENCY (%)
100
90
80
70
60
50
40
30
20
10
0
I
OUT
= 1mA
THEORETICAL MAX
I
OUT
= 10mA
I
OUT
= 100mA
–50
8
7
6
5
4
TA = 25°C
TA = 90°C
TA = –45°C
SUPPLY VOLTAGE (V)
2.7
50
NO-LOAD INPUT CURRENT (µA)
NO-LOAD INPUT CURRENT (mA)
54
58
62
3
3.3
3.6 3.9
3204 G19
4.2
66
70
52
56
60
64
68
0
0.8
1.6
2.4
3.2
4.0
0.4
1.2
2.0
2.8
3.6
4.5
LTC3204B-5
LTC3204-5
LOAD CURRENT (mA)
0.01
0.1
EXCESS INPUT CURRENT (mA)
1
0.01 0.1 1 10 100
3204 G20
10
1000
LTC3204B-5
(N0N-BURST MODE
OPERATION)
LTC3204-5
(BURST-MODE
OPERATION)
VIN = 3.6V
(TA = 25°C, C
TYPICAL PERFOR A CE CHARACTERISTICS
U W
= CIN = C
FLY
= 2.2µF unless otherwise specified)
OUT
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
(LTC3204-5/LTC3204B-5 ONLY)
Load Regulation
No-Load Input Current vs
Supply Voltage Efficiency vs Supply Voltage
Output Load Capability at 4%
Below Regulation
LOAD
)
Extra Input Current vs Load Current
(IIN-2I
Effective Open-Loop Output
Resistance vs Temperature
V
V
OUT
2V/DIV
SHD
N
5V/DIV
VIN = 3.6V
I
OUT
Soft-Start Output Ripple Load Transient Response
OUT
= 100mA
500µs/DIV
V
OUT
20mV/DIV
(AC COUPLED)
VIN = 3.6V
I
OUT
= 100mA
500ns/DIV
(AC COUPLED)
I
OUT
V
OUT
50mV/DIV
100mA
60mA
VIN = 3.6V
I
= 60mA TO 100mA STEP
OUT
10µs/DIV
3204fa
5
LTC3204-3.3/LTC3204-5/
–
+
V
OUT
V
IN
SHDN
C
+
C
–
3204 BD
CHARGE
PUMP
1.2MHz
OSCILLATOR
SOFT-START
AND
SWITCH CONTROL
GND
5
4
1, 7
2
3
6
U U
U
PI FU CTIO S
BLOCK DIAGRA
W
LTC3204B-3.3/LTC3204B-5
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.
V
(Pin 3): Regulated Output Voltage. V
OUT
should be
OUT
bypassed with a low ESR ceramic capacitor providing at
least 2µF of capacitance as close to the pin as possible
for best performance.
C+ (Pin 4): Flying Capacitor Positive Terminal.
C– (Pin 5): Flying Capacitor Negative Terminal.
SHD
N (Pin 6): Active Low Shutdown Input. A low on
SHD
N disables the LTC3204-3.3/LTC3204-5/LTC3204B-3.3/
LTC3204B-5. This pin must not be allowed to float.
6
3204fa
(Refer to the Block Diagram)
OPERATIO
U
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
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
V
on the first phase of the clock. On the second phase
IN
of the clock it is stacked in series with VIN and connected
to V
flying capacitor continues at a free running frequency of
1.2MHz (typ).
Shutdown Mode
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, V
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 SHDN
pin. Since the SHDN 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.
. This sequence of charging and discharging the
OUT
is disconnected from VIN. The SHDN pin is a
OUT
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, V
storage capacitor.
Soft-Start
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.
Short-Circuit/Thermal Protection
and the choice of output
OUT
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 (V
less than approximately 0.8V.
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
OUT
) is
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
V
is removed.
OUT
3204fa
7
LTC3204-3.3/LTC3204-5/
η = = =
P
P
V I
V I
V
V
OUT
IN
OUT OUT
IN OUT
OUT
IN
•
• 2 2
R R
f C
OL S
OSC FLY
≅
∑
+2
1
•
I
V V
R
OUT
IN OUT
OL
=
2 –
V
I
f C
RIPPLE P P
OUT
OSC OUT
( )
•
−
≅
2
+
–
R
OL
I
OUTVOUT
2V
IN
3204 F01
+
–
APPLICATIO S I FOR ATIO
W UU U
3204 F02
TEMPERATURE (°C)
100
0 5
0
EFFECTIVE OPEN-LOOP OUTPUT RESISTANCE (Ω)
VIN = 2.7V
V
OUT
= 4.5V
–50
8
7
6
5
4
LTC3204B-3.3/LTC3204B-5
Power Efficiency
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:
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, I
100mA and V
regulating to 5V, the measured efficiency
OUT
is 81.8% which is in close agreement with the theoretical
83.3% calculation.
OUT
=
(f
), value of the flying capacitor (C
OSC
), the nonoverlap
FLY
time, the internal switch resistances (RS), and the ESR of
the external capacitors. A first order approximation for
ROL is given below:
S=1 TO 4
Typical ROL values as a function of temperature are shown
in Figure 2.
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,
2V
IN(MIN)
.
Figure 1. Equivalent Open-Loop Circuit
From Fig. 1, the available current is given by:
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
Figure 2. Typical ROL vs Temperature
VIN, V
Capacitor Selection
OUT
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 C
C
. These capacitors should be 1µF or greater. Tantalum
OUT
IN
and
and aluminum capacitors are not recommended because
of their high ESR.
The value of C
ripple for a given load current. Increasing the size of C
directly controls the amount of output
OUT
OUT
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:
3204fa
LTC3204-3.3/LTC3204-5/
R
V V
I f
C
L MIN
IN OUT
OUT OSC FLY
0
2 1
( )
–
•
= ≅
LTC3204-3.3/
LTC3204-5
0.22µF
2.2µF
V
IN
GND
1cm OF WIRE
10nH
V
IN
1
2
32005 F03
APPLICATIO S I FOR ATIO
W UU U
LTC3204B-3.3/LTC3204B-5
where f
1.2MHz) and C
is the oscillator frequency (typically
OSC
is the value of output charge storage
OUT
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/LTC3204B-
3.3/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 C
controls the amount of output ripple,
OUT
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.
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:
where f
is the switching frequency (1.2MHz) and C
OSC
FLY
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/
C
OUT
0603
C
IN
0603
C
FL
Y
0603
GND
V
OUT
V
IN
3204 F04
SHDN
C
+
C
–
P V V I
D IN OUT OUT
= ( – ) •2
APPLICATIO S I FOR ATIO
W UU U
LTC3204B-3.3/LTC3204B-5
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 www.avxcorp.com
Kemet www.kemet.com
Murata www.murata.com
Taiyo Yuden www.t-yuden.com
Vishay 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/LTC3204B-
3.3/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.
10
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:
This derating curve assumes a maximum thermal resistance, θJA, of 80°C/W for the 2mm × 2mm DFN package.
3204fa
LTC3204-3.3/LTC3204-5/
PACKAGE DESCRIPTIO
U
AMBIENT TEMPERATURE (C)
POWER DISSIPATION (W)
3204 G05
3.0
2.5
2.0
1.5
1.0
0.5
0
–50
0
50
75
–25 25
100
125
150
2.00 ±0.10
(4 SIDES)
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
0.38 ± 0.05
BOTTOM VIEW—EXPOSED PAD
0.56 ± 0.05
(2 SIDES)
0.75 ±0.05
R = 0.115
TYP
1.37 ±0.05
(2 SIDES)
1
3
64
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
0.200 REF
0.00 – 0.05
(DC6) DFN 1103
0.25 ± 0.05
1.42 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
0.61 ±0.05
(2 SIDES)
1.15 ±0.05
0.675 ±0.05
2.50 ±0.05
PACKAGE
OUTLINE
0.25 ± 0.05
0.50 BSC
0.50 BSC
PIN
1
CHAMFER OF
EXPOSED PAD
APPLICATIO S I FOR ATIO
W UU U
LTC3204B-3.3/LTC3204B-5
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.
Figure 5. Maximum Power Dissipation
vs Ambient Temperature
Operation out of this curve will cause the junction temperature to exceed 160°C which may trigger the thermal
shutdown.
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
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.
DC Package
6-Lead Plastic DFN (2mm × 2mm)
(Reference LTC DWG # 05-08-1703)
However,
3204fa
11
LTC3204-3.3/LTC3204-5/
RELATED PARTS
2
5 4
LTC3204-5
2.2µF
2.2µF2.2µF
6
3
1, 7
32005 TA05
V
OUT
5V ±4%
C
–
C
+
V
IN
V
OUT
GND
SHDN
TYPICAL APPLICATIO S
U
3V TO 4.4V
Li-Ion
BATTERY
C
–
C
+
V
IN
5 4
V
OUT
LTC3204-5/
LTC3204B-5
GNDSHDN
3
1, 7
2
2.2µF
6
2.2µF 2.2µF
3200-5 TA03
DRIVE UP TO 5 LEDS
ON
OFF
V
SHDN
(APPLY PWM WAVEFORM FOR
ADJUSTABLE BRIGHTNESS CONTROL)
t
100Ω 100Ω 100Ω 100Ω 100Ω
OFF ON
V
IN
GND
SHDN
V
OUT
V
OUT
3.3V
C
–
C
+
LTC3204-3.3/
LTC3204B-3.3
2.2µF 2.2µF
2.2µF
V
IN
1.8V TO 4.5V
3204 TA02
1, 7
2
3
4
5
6
LTC3204B-3.3/LTC3204B-5
Regulated 3.3V Output
Lithium-Ion Battery to 5V White or Blue LED Driver
PART NUMBER DESCRIPTION COMMENTS
LTC1751-3.3/ 100mA, 800kHz Regulated Doubler VIN: 2V to 5V, V
LTC1751-5 ISD <2µA, MS8 Package
LTC1983-3/ 100mA, 900kHz Regulated Inverter VIN: 3.3V to 5.5V, V
LTC1983-5 ISD <1µA, ThinSOT Package
LTC3200-5 100mA, 2MHz Low Noise, Doubler/ VIN: 2.7V to 4.5V, V
White LED Driver ISD <1µA, ThinSOT Package
LTC3202 125mA, 1.5MHz Low Noise, Fractional VIN: 2.7V to 4.5V, V
White LED Driver ISD <1µA, DFN, MS Packages
12
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
USB Port to Regulated 5V Power Supply
OUT(MAX)
= 3.3V/5V, IQ = 20µA,
= –3V/–5V, IQ = 25µA,
OUT(MAX)
= 5V, IQ = 3.5mA,
OUT(MAX)
= 5.5V, IQ = 2.5mA,
OUT(MAX)
3204fa
LT/LT 0605 • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 2004
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