LTC3204B-5 [Linear]
Low Noise Regulated Charge Pump in 2 X 2 DFN; 低噪声稳压电荷泵的2× 2 DFN
| 型号： | LTC3204B-5 |
| 厂家： | 
Linear |
| 描述： | Low Noise Regulated Charge Pump in 2 X 2 DFN |
| 文件： | 总12页 (文件大小：608K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
Low Noise Regulated
Charge Pump in 2 × 2 DFN
FEATURES
DESCRIPTIO
TheLTC®3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
are low noise, constant frequency (1.2MHz) switched ca-
pacitorvoltagedoublers.TheLTC3204-3.3/LTC3204B-3.3
can produce a regulated output voltage of 3.3V
from a minimum input voltage of 1.8V (2 alkaline cells)
whereastheLTC3204-5/LTC3204B-5canproduce5Vfrom
a minimum of 2.7V (Li-Ion battery) input.
■
Fixed 3.3V or 5V Outputs
IN
■
V 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 I = 48µA
■
■
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
frequencyoperationatanyload.Built-insoft-startcircuitry
preventsexcessiveinrushcurrentduringstart-up.Thermal
shutdown and current-limit circuitry allow the parts to
Q
(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
survive a continuous short-circuit from V
to GND.
OUT
High switching frequency minimizes overall solution
footprint by allowing the use of tiny ceramic capaci-
tors. 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.
Short-Circuit/Thermal Protection
Available in Low UProfile 6-Lead DFN Package
APPLICATIO S
■
2 AA Cell to 3.3V
Li-Ion to 5V
USB On-The-Go Devices
White LED Drivers
Handheld Devices
■
■
, 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
Output Ripple vs Load Current
30
OUTPUT CAPACITANCE = 2.2µF
IN
2.2µF
V
= 3.6V
25
20
15
10
5
4
5
–
+
C
C
2
3
2.7V TO 5.5V
V
V
OUT
5V
IN
2.2µF
LTC3204-5/
LTC3204B-5
2.2µF
LTC3204-5
1, 7
6
GND
LTC3204B-5
OFF ON
SHDN
3204 TA01a
0
0
50
75
100
125
150
25
OUTPUT CURRENT (mA)
3204 TA01b
3204fa
1
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
ABSOLUTE AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
(Note 1)
ORDER PART
NUMBER
V to GND...................................................–0.3V to 6V
IN
V
OUT
to GND .............................................–0.3V to 5.5V
LTC3204EDC-3.3
TOP VIEW
SHDN to GND...............................................–0.3V to 6V
Short-Circuit Duration............................. Indefinite
LTC3204EDC-5
V
LTC3204BEDC-3.3
OUT
GND
1
2
3
6
5
4
SHDN
Operating Temperature Range (Note 2) ...–40°C to 85°C
Storage Temperature Range.................. –65°C to 125°C
Maximum Junction Temperature .......................... 125°C
LTC3204BEDC-5
DC PART
MARKING
LBJV
–
7
V
C
IN
V
C+
OUT
DC PACKAGE
6-LEAD (2mm × 2mm) PLASTIC DFN
LBNK
T
= 125°C, θ = 80°C/W
JMAX
JA
LBVF
EXPOSED PAD IS GND (PIN 7)
MUST BE SOLDERED TO PCB
LBVG
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 T = 25°C, V = 2.4V (LTC3204-3.3/LTC3204B-3.3) or 3.6V (LTC3204-5/LTC3204B-5),
A
IN
SHDN = V , C = 2.2µF, C = 2.2µF, C
= 2.2µF unless otherwise noted.
IN FLY
IN
OUT
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
Input Voltage Range
(LTC3204-3.3/LTC3204B-3.3)
(LTC3204-5/LTC3204B-5)
●
●
1.8
2.7
4.5
5.5
V
V
IN
V
Output Voltage Range
No Load Input Current
1.8V < V < 4.5V, I
< 40mA
OUT
IN
OUT
OUT
1.9V < V < 4.5V, I
< 50mA (LTC3204-3.3/LTC3204B-3.3)
●
●
3.168
4.8
3.3
5
3.432
5.2
V
V
IN
2.7V < V < 5.5V, I
< 65mA
IN
OUT
OUT
3.1V < V < 5.5V, I
< 150mA (LTC3204-5/LTC3204B-5)
IN
I
IN
I
I
I
I
= 0 (LTC3204-3.3)
= 0 (LTC3204-5)
= 0 (LTC3204B-3.3)
= 0 (LTC3204B-5)
48
60
1.25
3.6
µA
µA
mA
mA
OUT
OUT
OUT
OUT
I
I
Shutdown Current
SHDN = 0V, V
= 0V
OUT
1
µA
SHDN
Burst Mode Threshold
(LTC3204-3.3)
(LTC3204-5)
15
20
mA
mA
BURST
V
Output Ripple
I
= 100mA
20
82
mV
P-P
R
OUT
η
Efficiency
V
= 3V, I
= 100mA (LTC3204-5/LTC3204B-5)
OUT
%
IN
f
Switching Frequency
SHDN Input Threshold
SHDN Input Threshold
SHDN Input Current
SHDN Input Current
●
●
●
●
●
0.6
1.3
1.2
1.8
MHz
V
OSC
V
V
IH
IL
0.4
1
V
I
IH
I
IL
–1
–1
µA
µA
SHDN = 0V
1
R
OL
Effective Open-Loop Output
Resistance (Note 3)
V
IN
V
IN
= 1.8V, V
= 2.7V, V
= 3V (LTC3204-3.3/LTC3204B-3.3)
= 4.5V (LTC3204-5/LTC3204B-5)
7
6
Ω
Ω
OUT
OUT
I
Output Current Limit
Soft-Start Time
V
= OV
300
mA
ms
LIM
OUT
T
From the Rising Edge of SHDN to 90% of V
0.75
SS
OUT
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
Specifications over the –40°C to 85°C operating temperature range are
assured by design, characterization and correlation with statistical process
controls.
guaranteed to meet performance specifications from 0°C to 70°C.
Note 3: R ≡ (2V – V )/I
OL IN OUT OUT
3204fa
2
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
TYPICAL PERFOR A CE CHARACTERISTICS
(T = 25°C, C = C = C = 2.2µF unless otherwise specified)
OUT
A
FLY
IN
Oscillator Frequency vs
Supply Voltage
Oscillator Frequency vs
Temperature
SHDN Threshold Voltage vs
Supply Voltage
1.50
1.4
0.9
0.8
0.7
0.6
0.5
V
= 4.5V
IN
1.25
1.00
0.75
0.50
0.25
0
1.3
1.2
1.1
1.0
0.9
0.8
LOW-TO-HIGH THRESHOLD
V
V
= 2.4V
= 1.8V
IN
IN
HIGH-TO-LOW THRESHOLD
1.5
2.0
2.5
3.0
3.5
4.0
4.5
–50
–20
10
40
70
100
130
1.5
2.0
2.5
3.0
3.5
4.0
4.5
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
3204 G01
3204 G02
3204 G03
SHDN LO-to-HI Threshold vs
Temperature
SHDN HI-to-LO Threshold vs
Temperature
Short-Circuit Current vs Supply
0.9
0.8
0.7
0.6
0.5
0.8
0.7
0.6
0.5
0.4
350
300
250
200
150
100
50
V
= 3.2V
IN
V
V
= 3.2V
IN
IN
V
= 2.4V
IN
V
= 2.4V
IN
DEVICE CYCLES
IN AND OUT OF
THERMAL SHUTDOWN
= 1.8V
50
V
= 1.8V
IN
0
100
150
–50
50
TEMPERATURE (°C)
100
150
–50
0
0
1.5
2.5
3.0
3.5
4.0
4.5
2.0
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
3204 G06
3204 G04
3204 G05
3204fa
3
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
W U
TYPICAL PERFOR A CE CHARACTERISTICS
(LTC3204-3.3/LTC3204B-3.3 ONLY)
(T = 25°C, C = C = C = 2.2µF unless otherwise specified)
OUT
A
FLY
IN
Output Load Capability at 4%
Below Regulation
Effective Open-Loop Output
Resistance vs Temperature
Load Regulation
3.35
3.30
3.25
3.20
3.15
3.10
3.05
400
350
300
250
200
150
100
50
9
V
= 3.168V
V
V
= 1.8V
OUT
OUT
IN
= 3V
T
= 25°C
A
8
7
T
= 90°C
A
V
= 3.2V
IN
T
= –45°C
A
V
= 1.8V
IN
6
V
= 2.4V
300
IN
5
0
0
100
200
400
500
–50
50
0
TEMPERATURE (°C)
100
1.5
2.5
3.0
3.5
2.0
SUPPLY VOLTAGE (V)
LOAD CURRENT (mA)
3204 G09
3204 G08
3204 G07
Extra Input Current vs Load Current
(I -2I
No-Load Input Current vs
Supply Voltage
)
IN LOAD
Efficiency vs Supply Voltage
10
64
62
60
58
56
54
52
50
48
46
44
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
100
90
80
70
60
50
40
30
20
10
0
V
= 2.4V
IN
LTC3204B-3.3
(NON-BURST MODE
OPERATION)
THEORETICAL MAX
LTC3204B-3.3
1
0.1
I
= 30mA
OUT
I
= 1mA
OUT
LTC3204-3.3
(BURST MODE
OPERATION)
LTC3204-3.3
0.01
1.8
2.2 2.4 2.6
2.8
3
3.2
1.8
2.2 2.4 2.6
2.8 3.0 3.2
2
2.0
0.01
0.1
1
10
100
1000
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
LOAD CURRENT (mA)
3204 G12
3204 G11
3204 G10
Load Transient Response
V
Soft-Start Response
Output Ripple
OUT
V
OUT
20mV/DIV
V
OUT
2V/DIV
V
OUT
20mV/DIV
(AC COUPLED)
(AC COUPLED)
SHDN
2V/DIV
50mA
I
OUT
30mA
500µs/DIV
3204 G13
500ns/DIV
3204 G14
10µs/DIV
= 30mA TO 50mA STEP
3204 G15
V
LOAD
= 2.4V
V
LOAD
= 2.4V
V
OUT
= 2.4V
IN
IN
IN
I
= 50mA
I
= 50mA
I
3204fa
4
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
W U
(LTC3204-5/LTC3204B-5 ONLY)
TYPICAL PERFOR A CE CHARACTERISTICS
(T = 25°C, C = C = C = 2.2µF unless otherwise specified)
OUT
A
FLY
IN
Effective Open-Loop Output
Resistance vs Temperature
Output Load Capability at 4%
Below Regulation
Load Regulation
5.20
5.10
5.00
4.90
4.80
4.70
4.60
4.50
8
7
6
5
4
500
450
400
350
300
250
200
150
100
50
V
= 4.8V
OUT
V
V
= 2.7V
IN
OUT
= 4.5V
T
= 90°C
A
T
= 25°C
A
V
= 4.2V
IN
V
= 3.6V
IN
T
A
= –45°C
V
= 2.7V
IN
0
2.7
100
200
400
500
0 50
TEMPERATURE (°C)
0
300
–50
100
3.0
3.3
3.6
3.9
4.2
LOAD CURRENT (mA)
SUPPLY VOLTAGE (V)
3204 G18
3204 G17
3204 G16
Extra Input Current vs Load Current
(I -2I
No-Load Input Current vs
Supply Voltage
)
Efficiency vs Supply Voltage
IN LOAD
10
100
90
80
70
60
50
40
30
20
10
0
70
4.0
3.6
3.2
2.8
2.4
2.0
1.6
1.2
0.8
0.4
0
V
= 3.6V
IN
LTC3204-5
68
66
64
62
60
58
56
54
52
50
THEORETICAL MAX
LTC3204B-5
(N0N-BURST MODE
OPERATION)
1
0.1
I
= 100mA
OUT
LTC3204-5
(BURST-MODE
OPERATION)
I
= 10mA
OUT
I
= 1mA
OUT
LTC3204B-5
0.01
3.3
3.6
3.9
4.2
2.7
4.5
3.0
2.7
3
3.6
3.9
4.2
4.5
3.3
0.01
0.1
1
10
100
1000
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
LOAD CURRENT (mA)
3204 G21
3204 G20
3204 G19
V
Soft-Start
Output Ripple
Load Transient Response
OUT
V
OUT
2V/DIV
V
OUT
50mV/DIV
V
OUT
20mV/DIV
(AC COUPLED)
(AC COUPLED)
100mA
I
SHDN
5V/DIV
OUT
60mA
3204 G22
3204 G23
3204 G24
500µs/DIV
500ns/DIV
10µs/DIV
= 60mA TO 100mA STEP
V
OUT
= 3.6V
V
OUT
= 3.6V
V
OUT
= 3.6V
IN
IN
IN
I
= 100mA
I
= 100mA
I
3204fa
5
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
U U
U
PI FU CTIO S
+
GND (Pin 1, 7): Ground. These pins should be tied to a
groundplaneforbestperformance.Theexposedpadmust
be soldered to PCB ground to provide electrical contact
and optimum thermal performance.
C (Pin 4): Flying Capacitor Positive Terminal.
–
C (Pin 5): Flying Capacitor Negative Terminal.
SHDN (Pin 6): Active Low Shutdown Input. A low on
SHDNdisablestheLTC3204-3.3/LTC3204-5/LTC3204B-3.3/
LTC3204B-5. This pin must not be allowed to float.
V (Pin 2): Input Supply Voltage. V should be bypassed
IN
IN
with a 1µF to 4.7µF low ESR ceramic capacitor.
V
(Pin 3): Regulated Output Voltage. V should be
OUT
OUT
bypassed with a low ESR ceramic capacitor providing at
least 2µF of capacitance as close to the pin as possible
for best performance.
W
BLOCK DIAGRA
SOFT-START
6
SHDN
AND
SWITCH CONTROL
V
3
OUT
1.2MHz
OSCILLATOR
–
+
CHARGE
PUMP
+
4
5
C
V
2
IN
–
C
3204 BD
1, 7
GND
3204fa
6
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
U
(Refer to the Block Diagram)
OPERATIO
TheLTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
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 opera-
tion. 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
use a switched capacitor charge pump to boost V to a
IN
regulatedoutputvoltage.Regulationisachievedbysensing
the output voltage through an internal resistor divider and
modulating the charge pump output current based on the
errorsignal. A2-phasenonoverlappingclockactivatesthe
chargepumpswitches.Theflyingcapacitorischargedfrom
V on the first phase of the clock. On the second phase
IN
of the clock it is stacked in series with V and connected
IN
to V . This sequence of charging and discharging the
OUT
flying capacitor continues at a free running frequency of
1.2MHz (typ).
threshold varies with V , V
and the choice of output
IN OUT
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
TheLTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
havebuilt-insoft-startcircuitrytopreventexcessivecurrent
flowduringstart-up.Thesoft-startisachievedbycharging
an internal capacitor with a very weak current source. The
voltageonthiscapacitor, inturn, slowlyrampstheamount
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.
draws only leakage current from the V supply. Further-
IN
more, V
is disconnected from V . The SHDN pin is a
OUT
IN
CMOSinputwithathresholdvoltageofapproximately0.7V.
TheLTC3204-3.3/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.
Short-Circuit/Thermal Protection
TheLTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
havebuilt-inshort-circuitcurrentlimitaswellasover-tem-
perature protection. During a short-circuit condition, they
willautomaticallylimittheiroutputcurrenttoapproximately
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
pumponcethejunctiontemperatureexceedsapproximately
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-5will
cycle in and out of thermal shutdown indefinitely without
latchup or damage until the short-circuit condition on
Since the output voltages of these devices can go above
the input voltage, special circuitry is required to control
theinternallogic.Detectionlogicwilldrawaninputcurrent
of 5µA when the devices are in shutdown. However, this
current will be eliminated if the output voltage (V ) is
OUT
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
V
is removed.
OUT
3204fa
7
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
U U
W U
APPLICATIO S I FOR ATIO
Power Efficiency
(f ), value of the flying capacitor (C ), the nonoverlap
OSC FLY
time, the internal switch resistances (R ), and the ESR of
S
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:
the external capacitors. A first order approximation for
R
OL
is given below:
1
ROL ≅ 2 R +
∑
S
f
OSC•CFLY
S=1 TO 4
Typical R values as a function of temperature are shown
OL
in Figure 2.
POUT VOUT •IOUT VOUT
η =
=
=
P
V •2IOUT
2V
IN
8
IN
IN
V
V
= 2.7V
IN
OUT
= 4.5V
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 expres-
7
6
5
4
sion above is valid. For example, with V = 3V, I
=
IN
OUT
100mA and V
regulating to 5V, the measured efficiency
OUT
is 81.8% which is in close agreement with the theoretical
83.3% calculation.
Maximum Available Output Current
0
50
–50
100
TEMPERATURE (°C)
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
3204 F02
Figure 2. Typical R vs Temperature
OL
output resistance, R , and the effective input voltage,
OL
V , V
IN OUT
Capacitor Selection
2V
.
IN(MIN)
R
OL
ThestyleandvalueofcapacitorsusedwiththeLTC3204-3.3/
LTC3204-5/LTC3204B-3.3/LTC3204B-5determineseveral
important parameters such as regulator control loop sta-
bility, output ripple, charge pump strength and minimum
start-up time.
+
–
+
2V
IN
I
V
OUT
OUT
–
3204 F01
Figure 1. Equivalent Open-Loop Circuit
To reduce noise and ripple, it is recommended that low
ESR (<0.1Ω) ceramic capacitors be used for both C and
IN
From Fig. 1, the available current is given by:
C
OUT
. These capacitors should be 1µF or greater. Tantalum
2V – VOUT
IN
and aluminum capacitors are not recommended because
of their high ESR.
IOUT
=
ROL
The value of C
directly controls the amount of output
OUT
Effective Open Loop Output Resistance (R )
OL
ripple for a given load current. Increasing the size of C
OUT
Theeffectiveopenloopoutputresistance(R )ofacharge
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:
OL
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
IOUT
VRIPPLE(P−P)
≅
2fOSC•COUT
3204fa
8
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
U U
W U
APPLICATIO S I FOR ATIO
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.
where f
1.2MHz) and C
capacitor.
is the oscillator frequency (typically
OUT
OSC
is the value of output charge storage
Also,thevalueandstyleoftheoutputcapacitorcansignifi-
cantly 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 out-
put 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.
1cm OF WIRE
10nH
2
V
IN
LTC3204-3.3/
LTC3204-5
V
IN
2.2µF
0.22µF
1
GND
32005 F03
Figure 3. 10nH Inductor Used for
Additional Input Noise Reduction
Flying Capacitor Selection
ExcessiveESRontheoutputcapacitorcandegradetheloop
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
typicallyhaveexceptionalESRperformanceandcombined
with a good board layout should yield very good stability
and load transient performance.
Warning: A polarized capacitor such as tantalum or
aluminum should never be used for the flying capaci-
tor 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 fly-
ing capacitor.
Forverylightloadapplications,theflyingcapacitormaybe
reducedtosavespaceorcost.Fromthefirstorderapproxi-
As the value of C
controls the amount of output ripple,
OUT
the value of C controls the amount of ripple present at
mation of R in the section “Effective Open-Loop Output
IN
OL
the input pin (V ). The input current to the LTC3204-3.3/
Resistance,” the theoretical minimum output resistance
of a voltage doubling charge pump can be expressed by
the following equation:
IN
LTC3204-5/LTC3204B-3.3/LTC3204B-5 will be relatively
constant during the input charging phase or the output
chargingphasebutwilldroptozeroduringthenonoverlap
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.
2V – VOUT
1
IN
R0L(MIN)
=
≅
IOUT
fOSC•CFLY
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, theaboveexpressioncanbeusedasaguide-
line in determining a starting capacitor value.
Furtherinputnoisereductioncanbeachievedbypowering
the LTC3204-3.3/LTC3204-5/LTC3204B-3.3/LTC3204B-5
3204fa
9
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
U U
W U
APPLICATIO S I FOR ATIO
Ceramic Capacitors
Ceramiccapacitorsofdifferentmaterialslosetheircapaci-
tancewithhighertemperatureandvoltageatdifferentrates.
For example, a capacitor made of X5R or X7R material
will retain most of its capacitance from –40°C to 85°C
whereasaZ5UorY5Vstylecapacitorwillloseconsiderable
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
isapplied.Thereforewhencomparingdifferentcapacitors,
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 avail-
able inthesame0603 case. Infact, formost LTC3204-3.3/
LTC3204-5/LTC3204B-3.3/LTC3204B-5applications,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.
C
0603
IN
GND
SHDN
C–
V
IN
V
OUT
C
FLY
0603
C
C+
OUT
0603
3204 F04
Figure 4. Recommended Layout
Thermal Management
For higher input voltages and maximum output cur-
rent, 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.
Below is a list of ceramic capacitor manufacturers and
how to contact them:
AVX
www.avxcorp.com
www.kemet.com
Kemet
Murata
Taiyo Yuden
Vishay
TDK
www.murata.com
www.t-yuden.com
www.vishay.com
Derating Power at High Temperatures
To prevent an overtemperature condition in high power
applications, Figure 5 should be used to determine the
maximumcombinationofambienttemperatureandpower
dissipation.
www.component.tdk.com
Layout Considerations
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
dissipationintheLTC3204-3.3/LTC3204-5/LTC3204B-3.3/
LTC3204B-5 is given by the expression:
Due to the high switching frequency and high transient
currentsproducedbyLTC3204-3.3/LTC3204-5/LTC3204B-
3.3/LTC3204B-5, careful board layout is necessary for
optimum performance. A true ground plane and short
connectionstoalltheexternalcapacitorswillimproveper-
formanceandensureproperregulationunderallconditions.
Figure 4 shows an example layout for the LTC3204-3.3/
LTC3204-5/LTC3204B-3.3/LTC3204B-5.
PD = (2V – VOUT )•IOUT
IN
This derating curve assumes a maximum thermal resis-
tance, θ , of 80°C/W for the 2mm × 2mm DFN package.
JA
3204fa
10
LTC3204-3.3/LTC3204-5/
LTC3204B-3.3/LTC3204B-5
U U
W U
APPLICATIO S I FOR ATIO
Operation out of this curve will cause the junction tem-
perature to exceed 160°C which may trigger the thermal
shutdown.
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.
3.0
2.5
2.0
1.5
1.0
0.5
0
–50
50
100 125
150
–25
0
25
75
AMBIENT TEMPERATURE (C)
3204 G05
Figure 5. Maximum Power Dissipation
vs Ambient Temperature
PACKAGE DESCRIPTIO
DC Package
6-Lead Plastic DFN (2mm × 2mm)
(Reference LTC DWG # 05-08-1703)
R = 0.115
TYP
0.56 ± 0.05
(2 SIDES)
0.38 ± 0.05
4
6
0.675 ±0.05
2.50 ±0.05
1.15 ±0.05
0.61 ±0.05
(2 SIDES)
2.00 ±0.10
(4 SIDES)
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
PIN 1
PACKAGE
OUTLINE
CHAMFER OF
EXPOSED PAD
(DC6) DFN 1103
3
1
0.25 ± 0.05
0.25 ± 0.05
0.50 BSC
0.50 BSC
0.75 ±0.05
0.200 REF
1.37 ±0.05
(2 SIDES)
1.42 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
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
InformationfurnishedbyLinearTechnologyCorporationisbelievedtobeaccurateandreliable.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
U
TYPICAL APPLICATIO S
Regulated 3.3V Output
2.2µF
4
5
+
–
C
C
2
V
3
V
IN
OUT
V
V
OUT
IN
1.8V TO 4.5V
3.3V
LTC3204-3.3/
LTC3204B-3.3
2.2µF
2.2µF
1, 7
6
GND
OFF ON
SHDN
3204 TA02
Lithium-Ion Battery to 5V White or Blue LED Driver
2.2µF
5
4
–
+
C
C
V
DRIVE UP TO 5 LEDS
100Ω 100Ω
2
6
3
V
IN
OUT
3V TO 4.4V
Li-Ion
BATTERY
100Ω
100Ω
100Ω
2.2µF
2.2µF
LTC3204-5/
LTC3204B-5
1, 7
SHDN
GND
ON OFF
(APPLY PWM WAVEFORM FOR
ADJUSTABLE BRIGHTNESS CONTROL)
V
SHDN
3200-5 TA03
t
USB Port to Regulated 5V Power Supply
2.2µF
5
4
+
–
C
C
2
6
3
V
V
IN
OUT
LTC3204-5
V
OUT
2.2µF
2.2µF
5V ±4%
SHDN
GND
1, 7
32005 TA05
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
V : 2V to 5V, V
LTC1751-3.3/
LTC1751-5
100mA, 800kHz Regulated Doubler
= 3.3V/5V, I = 20µA,
OUT(MAX) Q
IN
I
<2µA, MS8 Package
SD
LTC1983-3/
LTC1983-5
100mA, 900kHz Regulated Inverter
V : 3.3V to 5.5V, V
= –3V/–5V, I = 25µA,
Q
IN
OUT(MAX)
I
<1µA, ThinSOT Package
SD
LTC3200-5
100mA, 2MHz Low Noise, Doubler/
White LED Driver
V : 2.7V to 4.5V, V
= 5V, I = 3.5mA,
Q
IN
OUT(MAX)
I
<1µA, ThinSOT Package
SD
LTC3202
125mA, 1.5MHz Low Noise, Fractional
White LED Driver
V : 2.7V to 4.5V, V
= 5.5V, I = 2.5mA,
OUT(MAX) Q
IN
I
<1µA, DFN, MS Packages
SD
3204fa
LT/LT 0605 • PRINTED IN USA
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
12
●
●
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
LINEAR TECHNOLOGY CORPORATION 2004
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