LT1054CSW#TRPBF [Linear Systems]

LT1054 - Switched-Capacitor Voltage Converter with Regulator; Package: SO; Pins: 16; Temperature Range: 0°C to 70°C;
LT1054CSW#TRPBF
型号: LT1054CSW#TRPBF
厂家: Linear Systems    Linear Systems
描述:

LT1054 - Switched-Capacitor Voltage Converter with Regulator; Package: SO; Pins: 16; Temperature Range: 0°C to 70°C

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LTC3261  
High Voltage,  
Low Quiescent Current  
Inverting Charge Pump  
FEATURES  
DESCRIPTION  
The LTC®3261 is a high voltage inverting charge pump  
that operates over a wide 4.5V to 32V input range and  
is capable of delivering up to 100mA of output current.  
n
4.5V to 32V V Range  
IN  
n
n
n
n
Inverting Charge Pump Generates –V  
IN  
60μA Quiescent Current in Burst Mode® Operation  
Charge Pump Output Current Up to 100mA  
50kHz to 500kHz Programmable Oscillator  
Frequency  
The charge pump employs either low quiescent current  
Burst Mode operation or low noise constant frequency  
mode. In Burst Mode operation the charge pump V  
OUT  
n
n
Short-Circuit/Thermal Protection  
Low Profile Thermally Enhanced 12-Pin MSOP  
Package  
regulates to –0.94 • V and the LTC3261 draws only 60μA  
IN  
ofquiescentcurrent.Inconstantfrequencymodethecharge  
pump produces an output equal to –V and operates at  
IN  
a fixed 500kHz or to a programmed frequency between  
50kHz to 500kHz using an external resistor. The LTC3261  
isavailableinathermallyenhanced12-pinMSOPpackage.  
APPLICATIONS  
n
Bipolar/Inverting Supplies  
n
Industrial/Instrumentation Bias Generators  
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks  
and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the  
property of their respective owners.  
n
Portable Medical Equipment  
n
Portable Instruments  
TYPICAL APPLICATION  
15V to –15V Inverter  
1μF  
VOUT Ripple  
+
C
C
V
OUT  
MODE = L  
MODE = H  
V
V
= –14.8V  
= –14.1V  
OUT  
OUT  
10mV/DIV  
–15V  
15V  
V
V
OUT  
IN  
AC-COUPLED  
10μF  
10μF  
LTC3261  
V
EN  
MODE  
OUT  
200mV/DIV  
AC-COUPLED  
RT  
GND  
3261 TA01a  
100μs/DIV  
V
= 15V  
= 500kHz  
= 5mA  
3261 TA01  
IN  
f
I
OSC  
OUT  
3261f  
1
LTC3261  
ABSOLUTE MAXIMUM RATINGS  
PIN CONFIGURATION  
(Notes 1, 3)  
TOP VIEW  
V , EN, MODE.. ......................................... –0.3V to 36V  
OUT  
RT................................................................ –0.3V to 6V  
IN  
1
2
3
4
5
6
NC  
RT  
NC  
12 NC  
11 MODE  
10 EN  
V
........................................................... –36V to 0.3V  
13  
GND  
V
9
8
7
V
C
NC  
OUT  
IN  
+
V
Short-Circuit Duration............................. Indefinite  
C
OUT  
NC  
Operating Junction Temperature Range  
MSE PACKAGE  
(Note 2).................................................. –40°C to 125°C  
Storage Temperature Range ................. –65°C to 150°C  
Lead Temperature (Soldering, 10 sec)...................300°C  
12-LEAD PLASTIC MSOP  
T
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB  
= 150°C, θ = 40°C/W  
JMAX  
JA  
ORDER INFORMATION  
LEAD FREE FINISH  
LTC3261EMSE#PBF  
LTC3261IMSE#PBF  
TAPE AND REEL  
PART MARKING*  
3261  
PACKAGE DESCRIPTION  
TEMPERATURE RANGE  
LTC3261EMSE#TRPBF  
LTC3261IMSE#TRPBF  
12-Lead Plastic MSOP  
12-Lead Plastic MSOP  
–40°C to 125°C  
–40°C to 125°C  
3261  
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.  
Consult LTC Marketing for information on non-standard lead based finish parts.  
For more information on lead free part marking, go to: http://www.linear.com/leadfree/  
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/  
3261f  
2
LTC3261  
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating  
temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = EN = 12V, MODE = 0V, RT = 200kΩ.  
SYMBOL  
PARAMETER  
CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
Charge Pump  
l
V
V
Input Voltage Range  
4.5  
3.4  
32  
4
V
IN  
l
l
V
Undervoltage Lockout Threshold  
V
IN  
V
IN  
Rising  
Falling  
3.8  
3.6  
V
V
UVLO  
IN  
I
V
Quiescent Current  
Shutdown, = EN = 0V  
2
60  
3.5  
5
120  
5.5  
μA  
μA  
mA  
VIN  
IN  
MODE = V , I  
= 0mA  
= 0mA  
IN VOUT  
MODE = 0V, I  
VOUT  
V
V
RT Regulation Voltage  
Regulation Voltage  
1.200  
V
RT  
V
MODE = 12V  
MODE = 0V  
–0.94 • V  
IN  
V
V
OUT  
OUT  
–V  
IN  
f
Oscillator Frequency  
RT = GND  
450  
100  
0.4  
500  
32  
550  
KHz  
Ω
OSC  
R
Charge Pump Output Impedance  
MODE = 0V, RT = GND  
OUT  
l
l
l
I
Max I  
Short-Circuit Current  
V
V
V
= GND, RT = GND  
160  
1.1  
1.0  
0.7  
1.1  
1.0  
0.7  
250  
2
mA  
V
SHORT_CKT  
VOUT  
OUT  
V
V
MODE Threshold Rising  
MODE(H)  
MODE(L)  
MODE  
MODE Threshold Falling  
V
I
MODE Pin Internal Pull-Down Current  
EN Threshold Rising  
= MODE = 32V  
= EN = 32V  
μA  
V
IN  
IN  
l
l
V
V
2
EN(H)  
EN Threshold Falling  
0.4  
V
EN(L)  
I
EN Pin Internal Pull-Down Current  
μA  
EN  
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.  
conjunction with board layout, the rated package thermal impedance and  
other environmental factors.  
The junction temperature (T , in °C) is calculated from the ambient  
J
temperature (T , in °C) and power dissipation (P , in Watts) according to  
A
D
Note 2: The LTC3261 is tested under pulsed load conditions such that  
the formula:  
T ≈ T . The LTC3261E is guaranteed to meet specifications from  
J
A
T = T + (P • θ ),  
J
A
D
JA  
0°C to 85°C junction temperature. Specifications over the –40°C to  
125°C operating junction temperature range are assured by design,  
characterization and correlation with statistical process controls. The  
LTC3261I is guaranteed over the –40°C to 125°C operating junction  
temperature range. High junction temperatures degrade operating  
lifetimes; operating lifetime is derated for junction temperatures greater  
than 125°C. Note that the maximum ambient temperature consistent with  
these specifications is determined by specific operating conditions in  
where θ = 40°C/W is the package thermal impedance.  
JA  
Note 3: This IC includes overtemperature protection that is intended  
to protect the device during momentary overload conditions. Junction  
temperatures will exceed 150°C when overtemperature protection is  
active. Continuous operation above the specified maximum operating  
junction temperature may result in device degradation or failure.  
3261f  
3
LTC3261  
TYPICAL PERFORMANCE CHARACTERISTICS  
(TA = 25°C, CFLY = 1μF, CIN = COUT = 10μF unless otherwise noted)  
Oscillator Frequency  
vs Supply Voltage  
Oscillator Frequency vs RT  
Shutdown Current vs Temperature  
600  
500  
400  
300  
200  
100  
0
600  
500  
400  
300  
200  
100  
0
25  
20  
15  
10  
5
V
V
V
= 32V  
= 12V  
= 5V  
IN  
IN  
IN  
RT = GND  
RT = 200kΩ  
0
0
5
10  
15  
20  
25  
30  
35  
1
10  
100  
RT (kΩ)  
1000  
10000  
–50 –25  
0
25 50 75 100 125 150  
TEMPERATURE (°C)  
SUPPLY VOLTAGE (V)  
3261 G01  
3261 G02  
3261 G03  
Quiescent Current  
vs Supply Voltage  
(Constant Frequency Mode)  
Quiescent Current vs Temperature  
(Burst Mode Operation)  
Quiescent Current vs Temperature  
(Constant Frequency Mode)  
140  
120  
100  
80  
14  
12  
10  
8
9
8
7
6
5
4
3
2
1
0
f
f
f
= 500kHz  
= 200kHz  
= 50kHz  
V
= 12V  
RT = GND  
OSC  
OSC  
OSC  
IN  
f
f
f
= 500kHz  
= 200kHz  
= 50kHz  
OSC  
OSC  
OSC  
V
= 32V  
= 12V  
= 5V  
IN  
V
IN  
60  
6
V
IN  
40  
4
20  
2
0
0
–50 –25  
0
25 50 75 100 125 150  
TEMPERATURE (°C)  
0
5
10  
15  
20  
25  
30  
35  
–50 –25  
0
25 50 75 100 125 150  
TEMPERATURE (°C)  
SUPPLY VOLTAGE (V)  
3261 G04  
3261 G05  
3261 G06  
Effective Open-Loop Resistance  
vs Temperature  
VOUT Short-Circuit Current  
vs Supply Voltage  
VOUT Short Circuit Current  
vs Temperature  
60  
55  
50  
45  
40  
35  
30  
25  
20  
250  
200  
150  
100  
50  
200  
180  
160  
140  
120  
100  
V
V
V
= 32V  
= 25V  
= 12V  
f
= 500kHz  
V
= 12V  
IN  
IN  
IN  
IN  
OSC  
RT = GND  
f
= 500kHz  
= 200kHz  
20  
OSC  
f
OSC  
0
–50 –25  
0
25 50 75 100 125 150  
TEMPERATURE (°C)  
0
5
10  
15  
25  
30  
35  
–50 –25  
0
25  
50  
75 100 125  
SUPPLY VOLTAGE (V)  
TEMPERATURE (°C)  
3261 G07  
3261 G08  
3261 G8b  
3261f  
4
LTC3261  
TYPICAL PERFORMANCE CHARACTERISTICS  
(TA = 25°C, CFLY = 1μF, CIN = COUT = 10μF unless otherwise noted)  
Voltage Loss (VIN – |VOUT|)  
Effective Open-Loop Resistance  
vs Supply Voltage  
V
OUT Load Transient Burst Mode  
vs Output Current  
Operation (MODE = H)  
(Constant Frequency Mode)  
90  
80  
70  
60  
50  
40  
30  
20  
10  
0
3.0  
2.5  
2.0  
1.5  
1.0  
0.5  
0.0  
f
f
f
= 50kHz  
= 200kHz  
= 500kHz  
V
= 12V  
IN  
OSC  
OSC  
OSC  
V
OUT  
f
= 200kHz  
= 500kHz  
OSC  
OSC  
500mV/DIV  
AC-COUPLED  
–5mA  
f
I
OUT  
–50mA  
3261 G11  
V
OSC  
= 12V  
2ms/DIV  
IN  
f
= 500kHz  
0
5
10  
15  
20  
25  
30  
35  
0.1  
1
10  
100  
SUPPLY VOLTAGE (V)  
OUTPUT CURRENT (mA)  
3261 G10  
3261 G09  
VOUT Transient  
(MODE = Low to High)  
Average Input Current  
vs Output Current  
V
OUT Ripple  
100  
10  
1
V
OUT  
V
OUT  
MODE = L  
500mV/DIV  
10mV/DIV  
AC-COUPLED  
AC-COUPLED  
MODE = L  
V
MODE = H  
OUT  
200mV/DIV  
MODE  
MODE = H  
AC-COUPLED  
3261 G12  
3261 G14  
V
= 12V  
= 500kHz  
= –5mA  
2ms/DIV  
IN  
100μs/DIV  
V
f
= 12V  
OSC  
IN  
f
I
OSC  
OUT  
= 500kHz  
V
= 15V  
IN  
0.1  
f
I
= 500kHz  
= 5mA  
OSC  
OUT  
0.1  
1
10  
100  
OUTPUT CURRENT (mA)  
3261 G13  
3261f  
5
LTC3261  
PIN FUNCTIONS  
NC (Pins 1, 3, 6, 7,12): No Connect Pins. These pins are  
not connected to the LTC3261 die. These pins should be  
left floating or connected to ground. Pins 6 and 7 can also  
be shorted to adjacent pins.  
V (Pin9):InputVoltagefortheChargePump. V should  
IN IN  
be bypassed with a low impedance ceramic capacitor.  
EN (Pin 10): Logic Input. A logic “high” on the EN pin  
enables the inverting charge pump.  
RT(Pin2):InputConnectionforProgrammingtheSwitch-  
ing Frequency. The RT pin servos to a fixed 1.2V when  
the EN pin is driven to a logic “high”. A resistor from RT  
to GND sets the charge pump switching frequency. If the  
RT pin is tied to GND, the switching frequency defaults  
to a fixed 500kHz.  
MODE (Pin 12): Logic Input. The MODE pin deter-  
mines the charge pump operating mode. A logic “high”  
on the MODE pin forces the charge pump into Burst  
Mode operation regulating V  
to approximately  
OUT  
–0.94 • V with hysteretic control. A logic “low” on the  
IN  
MODE pin forces the charge pump to operate as an open-  
loop inverter with a constant switching frequency. The  
switching frequency in both modes is determined by an  
external resistor from the RT pin to GND. In Burst Mode,  
this represents the frequency of the burst cycles before  
the part enters the low quiescent current sleep state.  
V
(Pin 4): Charge Pump Output Voltage. In constant  
OUT  
frequency mode (MODE = low) this pin is driven to –V .  
IN  
InBurstModeoperation, (MODE=high)thispinvoltageis  
regulatedto0.94•V usinganinternalburstcomparator  
IN  
with hysteretic control.  
C (Pin 5): Flying Capacitor Negative Connection.  
GND (Exposed Pad Pin 13): Ground. The exposed pack-  
age pad is ground and must be soldered to the PC board  
groundplaneforproperfunctionalityandforratedthermal  
performance.  
+
C (Pin 8): Flying Capacitor Positive Connection.  
BLOCK DIAGRAM  
8
5
+
C
C
S1  
S4  
V
V
OUT  
IN  
9
4
S3  
S2  
EN  
CHARGE  
PUMP  
AND  
INPUT  
LOGIC  
10  
11  
50kHz  
TO  
500kHz  
OSC  
RT  
2
MODE  
GND  
13  
3261 BD  
3261f  
6
LTC3261  
OPERATION (Refer to the Block Diagram)  
The LTC3261 is a high voltage inverting charge pump. It  
supportsawideinputpowersupplyrangefrom4.5Vto32V.  
Thefrequencyofchargingcyclesissetbytheexternalresistor  
on the RT pin. The charge pump has a lower R at higher  
OL  
frequencies.ForBurstModeoperationitisrecommendedthat  
Shutdown Mode  
the RT pin be tied to GND. This minimizes the charge pump  
R , quickly charges the output up to the burst threshold  
OL  
In shutdown mode, all circuitry except the internal bias is  
turnedoff. TheLTC3261isinshutdownwhenalogiclowis  
applied to the enable input (EN). The LTC3261 only draws  
and optimizes the duration of the low current sleep state.  
600  
2μA (typical) from the V supply in shutdown.  
IN  
500  
400  
300  
200  
100  
0
Constant Frequency Operation  
The LTC3261 provides low noise constant frequency opera-  
tion when a logic low is applied to the MODE pin. The charge  
pump and oscillator circuit are enabled using the EN pin. At  
thebeginningofaclockcycle,switchesS1andS2areclosed.  
+
The external flying capacitor across the C and C pins is  
charged to the V supply. In the second phase of the clock  
IN  
1
10  
100  
1000  
10000  
cycle, switches S1 and S2 are opened, while switches S3  
RT (kΩ)  
+
and S4 are closed. In this configuration the C side of the  
3261 F01  
flying capacitor is grounded and charge is delivered through  
Figure 1. Oscillator Frequency vs RT  
the C pin to V . In steady state the V  
pin regulates at  
OUT  
OUT  
–V less any voltage drop due to the load current on V  
.
IN  
OUT  
Soft-Start  
The charge transfer frequency can be adjusted between  
50kHz and 500kHz using an external resistor on the RT  
pin. At slower frequencies the effective open-loop output  
The LTC3261 has built in soft-start circuitry to prevent  
excessive current flow during start-up. The soft-start is  
achievedbyinternalcircuitrythatslowlyrampstheamount  
of current available at the output storage capacitor. The  
soft-start circuitry is reset in the event of a commanded  
shutdown or thermal shutdown.  
resistance (R ) of the charge pump is larger and it is able  
OL  
to provide smaller average output current. Figure 1 can  
be used to determine a suitable value of RT to achieve a  
required oscillator frequency. If the RT pin is grounded,  
the part operates at a constant frequency of 500kHz.  
Short-Circuit/Thermal Protection  
Burst Mode Operation  
The LTC3261 has built-in short-circuit current limit as  
well as overtemperature protection. During a short-circuit  
condition, the part automatically limits its output current  
to approximately 160mA. If the junction temperature ex-  
ceedsapproximately175°Cthethermalshutdowncircuitry  
disables current delivery to the output. Once the junction  
temperature drops back to approximately 165°C current  
deliverytotheoutputisresumed.Whenthermalprotection  
is active the junction temperature is beyond the specified  
operating range. Thermal protection is intended for mo-  
mentary overload conditions outside normal operation.  
Continuous operation above the specified maximum op-  
erating junction temperature may impair device reliability.  
The LTC3261 provides low power Burst Mode operation  
when a logic high is applied to the MODE pin. In Burst  
Mode operation, the charge pump charges the V  
pin to  
OUT  
–0.94 • V (typical). The part then shuts down the internal  
IN  
oscillator to reduce 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 60μA. When the output  
voltage droops enough to overcome the burst comparator  
hysteresis,thepartwakesupandcommenceschargepump  
cycles until output voltage exceeds –0.94 • V (typical).  
IN  
This mode provides lower operating current at the cost of  
higher output ripple and is ideal for light load operation.  
3261f  
7
LTC3261  
APPLICATIONS INFORMATION  
Effective Open-Loop Output Resistance  
IOUT  
COUT  
1
f
OSC  
VRIPPLE(P-P)  
where f  
– tON  
Theeffectiveopen-loopoutputresistance(R )ofacharge  
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  
(f ), value of the flying capacitor (C ), the nonoverlap  
is the oscillator frequency t is the on-time  
of the oscillator (1μs) typical and C  
output capacitor.  
OSC  
ON  
is the value of the  
OUT  
OSC  
FLY  
time, the internal switch resistances (R ) and the ESR of  
S
Just as the value of C  
controls the amount of output  
OUT  
the external capacitors.  
ripple,thevalueofC controlstheamountofripplepresent  
IN  
Typical R values as a function of temperature are shown  
at the input (V ) pin. The amount of bypass capacitance  
OL  
IN  
in Figure 2  
required at the input depends on the source impedance  
driving V . For best results it is recommended that V  
IN  
IN  
60  
V
V
V
= 32V  
= 25V  
= 12V  
f
= 500kHz  
IN  
IN  
IN  
OSC  
be bypassed with at least 2μF of low ESR capacitance. A  
high ESR capacitor such as tantalum or aluminum will  
have higher input noise than a low ESR ceramic capacitor.  
Therefore, a ceramic capacitor is recommended as the  
main bypass capacitance with a tantalum or aluminum  
capacitor used in parallel if desired.  
55  
50  
45  
40  
35  
30  
25  
20  
Flying Capacitor Selection  
The flying capacitor controls the strength of the charge  
pump. A 1μF or greater ceramic capacitor is suggested  
for the flying capacitor for applications requiring the full  
rated output current of the charge pump.  
–50 –25  
0
25 50 75 100 125 150  
TEMPERATURE (°C)  
3261 F02  
Figure 2. Typical ROL vs Temperature  
For very light load applications, the flying capacitor may  
be reduced to save space or cost. For example, a 0.2μF  
capacitormightbesufficientforloadcurrentsupto20mA.  
A smaller flying capacitor leads to a larger effective open-  
loop resistance (R ) and thus limits the maximum load  
current that can be delivered by the charge pump.  
Input/Output Capacitor Selection  
The style and value of capacitors used with the LTC3261  
determineseveralimportantparameterssuchasregulator  
control loop stability, output ripple, charge pump strength  
andminimumturn-ontime.Toreducenoiseandripple,itis  
recommendedthatlowESRceramiccapacitorsbeusedfor  
thechargepumpoutput.Thechargepumpoutputcapacitor  
should retain at least 2μF of capacitance over operating  
temperature and bias voltage. Tantalum and aluminum  
capacitors can be used in parallel with a ceramic capacitor  
to increase the total capacitance but should not be used  
alone because of their high ESR. In constant frequency  
OL  
Ceramic Capacitors  
Ceramic capacitors of different materials lose their capaci-  
tancewithhighertemperatureandvoltageatdifferentrates.  
For example, a capacitor made of X5R or X7R material will  
retainmostofitscapacitancefrom40°Cto8Cwhereasa  
Z5UorY5Vstylecapacitorwillloseconsiderablecapacitance  
over that range. Z5U and Y5V capacitors may also have a  
poorvoltagecoefficientcausingthemtolose60%ormoreof  
theircapacitancewhentheratedvoltageisapplied.Therefore  
when comparing different capacitors, it is often more ap-  
propriate to compare the amount of achievable capacitance  
for a given case size rather than discussing the specified  
mode, the value of C  
directly controls the amount of  
OUT  
outputrippleforagivenloadcurrent.Increasingthesizeof  
will reduce the output ripple at the expense of higher  
C
OUT  
minimum turn-on time. The peak-to-peak output ripple at  
the V  
pin is approximately given by the expression:  
OUT  
capacitance value. The capacitor manufacture’s data sheet  
3261f  
8
LTC3261  
APPLICATIONS INFORMATION  
should be consulted to ensure the desired capacitance at  
all temperatures and voltages. Table 1 is a list of ceramic  
capacitor manufacturers and their websites.  
The power dissipated in the LTC3261 is:  
P = (V – |V |) • (I  
)
D
IN  
OUT  
OUT  
where I  
denotes output current at the V  
pin.  
OUT  
OUT  
Table 1  
ThederatingcurveinFigure4assumesamaximumthermal  
AVX  
Kemet  
www.avxcorp.com  
www.kemet.com  
resistance, θ , of 40°C/W for the package. This can be  
JA  
achieved from a printed circuit board layout with a solid  
ground plane and a good connection to the exposed pad  
of the LTC3261 package.  
Murata  
Taiyo Yuden  
Vishay  
www.murata.com  
www.t-yuden.com  
www.vishay.com  
It is recommended that the LTC3261 be operated in the  
TDK  
www.component.tdk.com  
region corresponding to T ≤ 150°C for continuous opera-  
J
Layout Considerations  
tion as shown in Figure 4. Short-term operation may be  
acceptablefor150°C<T <175°Cbutlong-termoperation  
Duetohighswitchingfrequencyandhightransientcurrents  
produced by LTC3261, careful board layout is necessary  
for optimum performance. A true ground plane and short  
connections to all the external capacitors will improve  
performanceandensureproperregulationunderallcondi-  
tions. Figure 3 shows an example layout for the LTC3261.  
J
in this region should be avoided as it may reduce the life of  
the part or cause degraded performance. For T > 175°C  
J
the part will be in thermal shutdown.  
GND  
+
C
The flying capacitor nodes C and C switch large currents  
at a high frequency. These nodes should not be routed  
close to sensitive pins such as the RT pin .  
FLY  
V
V
OUT  
IN  
Thermal Management  
EN  
MODE  
R
T
At high input voltages and maximum output current, there  
can be substantial power dissipation in the LTC3261. If  
the junction temperature increases above approximately  
175°C, the thermal shutdown circuitry will automatically  
deactivate the output. To reduce the maximum junction  
temperature, a good thermal connection to the PC board  
groundplaneisrecommended.Connectingtheexposedpad  
of the package 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.  
GND  
3261 F03  
Figure 3. Recommended Layout  
6
5
4
3
2
1
0
θ
JA  
= 40°C/W  
THERMAL  
SHUTDOWN  
T = 175°C  
J
Derating Power at High Temperatures  
RECOMMENDED  
OPERATION  
To prevent an overtemperature condition in high power  
applications, Figure 4 should be used to determine the  
maximumcombinationofambienttemperatureandpower  
dissipation.  
T = 150°C  
J
–50 –25  
0
25 50 75 100 125 150 175  
AMBIENT TEMPERATURE (°C)  
3261 F04  
The power dissipated in the LTC3261 should always fall  
under the line shown for a given ambient temperature.  
Figure 4. Maximum Power Dissipation vs Ambient Temperature  
3261f  
9
LTC3261  
TYPICAL APPLICATIONS  
High Input Divide by 2 Voltage Divider  
C2  
1μF  
50V  
+
C
C
9V TO 32V  
V
V
IN  
OUT  
C1  
4.7μF  
50V  
EN  
LTC3261  
MODE  
RT  
GND  
3261 TA04  
NOTE: MINIMUM LOAD OF  
120μA IS REQUIRED TO  
ASSURE START-UP  
V
/2  
IN  
C3  
4.7μF  
25V  
Inverting Charge Pump with Bipolar Doubler  
D1  
1N4148  
D2  
1N4148  
~ 2V  
IN  
C2  
1μF  
50V  
C5  
4.7μF  
100V  
4.5V TO 32V  
C
V
IN  
C3  
1μF  
50V  
C1  
4.7μF  
50V  
EN  
C
LTC3261  
C4  
D4  
1N4148  
1μF  
50V  
~ –2V  
IN  
IN  
C6  
D3  
1N4148  
MODE  
RT  
4.7μF  
100V  
–V  
V
OUT  
GND  
C7  
4.7μF  
50V  
3261 TA06  
NOTE: I  
ꢀtꢀꢁꢀꢂꢀ*  
ꢀtꢀꢁꢀꢂꢀ*  
< = 100mA  
OUT  
2VIN  
–2VIN  
High Voltage to Inverted Low Voltage Charge Pump  
4.5V TO 32V  
C1  
4.7μF  
50V  
V
V –V – |IOUT | tROL  
IN f  
OUT  
VOUT –  
–V  
f
V
V
IN  
OUT  
2
C4  
4.7μF  
50V  
EN  
+
C
C2  
1μF  
50V  
D1  
MBR0540  
LTC3261  
D2  
MBR0540  
C3  
1μF  
50V  
D3  
MBR0540  
C
RT  
MODE  
GND  
3261 TA07  
3261f  
10  
LTC3261  
PACKAGE DESCRIPTION  
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.  
MSE Package  
12-Lead Plastic MSOP, Exposed Die Pad  
(Reference LTC DWG # 05-08-1666 Rev F)  
BOTTOM VIEW OF  
EXPOSED PAD OPTION  
2.845 0.102  
(.112 .004)  
2.845 0.102  
(.112 .004)  
0.889 0.127  
(.035 .005)  
1
6
0.35  
REF  
1.651 0.102  
(.065 .004)  
5.23  
(.206)  
MIN  
1.651 0.102  
(.065 .004)  
3.20 – 3.45  
(.126 – .136)  
0.12 REF  
DETAIL “B”  
CORNER TAIL IS PART OF  
THE LEADFRAME FEATURE.  
FOR REFERENCE ONLY  
NO MEASUREMENT PURPOSE  
DETAIL “B”  
12  
4.039 0.102  
7
0.65  
(.0256)  
BSC  
0.42 0.038  
(.0165 .0015)  
TYP  
(.159 .004)  
(NOTE 3)  
0.406 0.076  
RECOMMENDED SOLDER PAD LAYOUT  
(.016 .003)  
12 11 10 9 8 7  
REF  
DETAIL “A”  
0.254  
(.010)  
3.00 0.102  
(.118 .004)  
(NOTE 4)  
0° – 6° TYP  
4.90 0.152  
(.193 .006)  
GAUGE PLANE  
0.53 0.152  
(.021 .006)  
1
2 3 4 5 6  
DETAIL “A”  
0.86  
(.034)  
REF  
1.10  
(.043)  
MAX  
0.18  
(.007)  
SEATING  
PLANE  
0.22 – 0.38  
(.009 – .015)  
TYP  
0.1016 0.0508  
(.004 .002)  
0.650  
(.0256)  
BSC  
MSOP (MSE12) 0911 REV F  
NOTE:  
1. DIMENSIONS IN MILLIMETER/(INCH)  
2. DRAWING NOT TO SCALE  
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.  
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE  
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.  
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE  
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX  
6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD SHALL  
NOT EXCEED 0.254mm (.010") PER SIDE.  
3261f  
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 representa-  
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.  
11  
LTC3261  
TYPICAL APPLICATION  
24V to –24V Inverter  
C2  
1μF  
8
5
+
C
C
9
4
2
–24V  
24V  
V
V
IN  
OUT  
C3  
10μF  
C1  
10μF  
LTC3261  
10  
11  
EN  
MODE  
RT  
GND  
13  
3261 TA03  
RELATED PARTS  
PART NUMBER  
DESCRIPTION  
COMMENTS  
LTC1144  
Switched-Capacitor Wide Input Range Voltage Converter with  
Shutdown  
Wide Input Voltage Range: 2V to 18V, I < 8μA,  
SD  
SO8 Package  
LTC1514/LTC1515  
LT®1611  
Step-Up/Step-Down Switched-Capacitor DC/DC Converters  
V : 2V to 10V, V : 3.3V to 5V, I = 60μA, SO8 Package  
IN  
OUT  
Q
150mA Output, 1.4MHz Micropower Inverting Switching Regulator V : 0.9V to 10V, V  
=
34V, ThinSOT™ Package  
IN  
OUT  
LT1614  
250mA Output, 600kHz Micropower Inverting Switching Regulator V : 0.9V to 6V, V  
= 30V, I = 1mA, MS8, SO8 Packages  
OUT Q  
IN  
LTC1911  
250mA, 1.5MHz Inductorless Step-Down DC/DC Converter  
V : 2.7V to 5.5V, V  
= 1.5V/1.8V, I = 180μA,  
Q
IN  
OUT  
MS8 Package  
LTC3250/LTC3250-1.2/ Inductorless Step-Down DC/DC Converters  
LTC3250-1.5  
V : 3.1V to 5.5V, V  
= 1.2V, 1.5V, I = 35μA,  
Q
IN  
OUT  
ThinSOT Package  
LTC3251  
500mA Spread Spectrum Inductorless Step-Down DC/DC  
Converter  
V : 2.7V to 5.5V, V : 0.9V to 1.6V, 1.2V, 1.5V, I = 9μA,  
IN  
OUT  
Q
MS10E Package  
LTC3252  
Dual 250mA, Spread Spectrum Inductorless Step-Down DC/DC  
Converter  
V : 2.7V to 5.5V, V : 0.9V to 1.6V, I = 50μA,  
IN  
OUT  
Q
DFN12 Package  
LT1054/LT1054L  
Switched-Capacitor Voltage Converters with Regulator  
V : 3.5V to 15V/7V, I  
= 100mA/125mA, N8, S08,  
IN  
OUT  
SO16 Packages  
3261f  
LT 0412 • PRINTED IN USA  
LinearTechnology Corporation  
1630 McCarthy Blvd., Milpitas, CA 95035-7417  
12  
© LINEAR TECHNOLOGY CORPORATION 2012  
(408) 432-1900 FAX: (408) 434-0507 www.linear.com  

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