LTC1550LCGN#PBF_技术文档

LTC1550/LTC1551

Low Noise, Switched

Capacitor Regulated

Voltage Inverters

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FEATURES

DESCRIPTION

The LTC^®1550/LTC1551 are switched capacitor charge

pump voltage inverters which include internal linear post-

regulators to minimize output ripple. Output voltages are

■

Regulated Negative Voltage from a Single

Positive Supply

■

Low Output Ripple: Less Than 1mV_P-PTyp

■

fixed at – 4.1V, with ripple voltages typically below 1mV_P-P

.

High Charge Pump Frequency: 900kHz Typ

■

The LTC1550 is also available in an adjustable output

voltage version. The LTC1550/LTC1551 are ideal for use

as bias voltage generators for GaAs transmitter FETs in

portable RF and cellular telephone applications.

Small Charge Pump Capacitors: 0.1µF

■

Requires Only Four External Capacitors

■

Fixed –4.1V or Adjustable Output

■

Shutdown Mode Drops Supply Current to < 1µA

■

High Output Current: Up to 10mA, V_CC= 5V

The LTC1550/LTC1551 operate from single 4.5V to 6.5V

supplies and draw typical quiescent currents of 4.25mA

with a 5V supply. Each device includes a TTL compatible

Shutdown pin which drops supply current to 0.2µA typi-

cally. The LTC1550 Shutdown pin is active low (SHDN),

while the LTC1551 Shutdown pin is active high (SHDN).

Only four external components are required: an input bypass

capacitor, two 0.1µF charge pump capacitors and a filter

capacitoratthelinearregulatoroutput.TheadjustableLTC1550

requirestwoadditionalresistorstosettheoutputvoltage.The

LTC1550/LTC1551 will supply up to 10mA output current

with a 5V supply, while maintaining guaranteed output

regulation of ±5%.

■

Output Regulation: 5%

■

Available in SO-8 and 16-Lead SSOP

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APPLICATIONS

■

GaAs FET Bias Generators

■

Negative Supply Generators

■

Battery-Powered Systems

Single Supply Applications

■

The fixed voltage LTC1550/LTC1551 are available in S0-8

plastic packages. The adjustable LTC1550 is available in a

16-pin SSOP.

, LTC and LT are registered trademarks of Linear Technology Corporation.

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TYPICAL APPLICATION

– 4.1V Generator with 1mV_P-PNoise

V_OUTOutput Noise and Ripple

1

2

8

V

CC

SHDN

SENSE

CP

7

V

CC

OUT

+

4.7µF

IN

C

CP

LTC1551

C

0.1µF

V_OUT

AC COUPLED

2mV/DIV

3

4

6

+

C1

GND

5

–

V

C1

OUT

FERRITE BEAD

V

LOAD

= –4.1V

= 5mA

OUT

I

C

OUT

L

+

10µF

0.1µF

C1

0.1µF

1550/51 F01

10µs/DIV

1550/51 TA02

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LTC1550/LTC1551

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ABSOLUTE MAXIMUM RATINGS

(Note 1)

Supply Voltage ......................................................... 7V

Output Voltage................................ 0.3V to (V_CC– 14V)

Total Voltage, V_CCto CP_OUT............................................. 14V

Input Voltage (SHDN Pin) ........... –0.3V to (V_CC+ 0.3V)

Input Voltage (REG Pin)............................ – 0.3V to 12V

Output Short-Circuit Duration.............................. 30 sec

Commercial Temperature Range ................. 0°C to 70°C

Extended Commercial Operating

Temperature Range (Note 3) .............. –40°C to 85°C

Industrial Temperature Range ................ – 40°C to 85°C

Storage Temperature Range ................ –65°C to 150°C

Lead Temperature (Soldering, 10 sec)................. 300°C

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PACKAGE/ORDER INFORMATION

TOP VIEW

ORDER

NC

+

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

V

CC

PART NUMBER

TOP VIEW

C1

SHDN

REG

SHDN*

1

2

3

4

8

7

6

5

SENSE

NC

LTC1550CS8-4.1

LTC1551CS8-4.1

LTC1550CGN

LTC1550IGN

V

CC

CP

OUT

V

SENSE

ADJ

OUT

+

C1

GND

–

C1

–

V

C1

OUT

PGND

AGND

NC

CP

NC

OUT

S8 PACKAGE

8-LEAD PLASTIC SO

GN PART MARKING

1550

*SHDN FOR LTC1550, SHDN FOR LTC1551

GN PACKAGE

16-LEAD PLASTIC SSOP

T_JMAX= 150°C, θ_JA= 150°C/ W

Consult factory for Military grade parts.

ELECTRICAL CHARACTERISTICS

V_CC= 4.5V to 6.5V, C1 = C2 = 0.1µF, C_OUT= 10µF, T_A= 25°C unless otherwise specified. (Note 3)

SYMBOL PARAMETER CONDITIONS

MIN

TYP

MAX

UNITS

V

Supply Voltage

(LTC1550CGN/LTC1550IGN)

(LTC1550CS8-4.1/LTC1551CS8-4.1)

CC

●

2.7

4.5

6.5

V

Reference Voltage

Supply Current

●

1.24

4.25

0.2

900

0.1

15

V

mA

µA

kHz

V

mA

V

µA

ms

REF

I

f

V

= 5V, V

= V (LTC1550) or GND (LTC1551)

●

7

10

S

CC

SHDN

CC

= GND (LTC1550) or V (LTC1551)

CC

Internal Oscillator Frequency

REG Output Low Voltage

REG Sink Current

SHDN Input High Voltage

SHDN Input Low Voltage

SHDN Input Current

OSC

V

I

= 1mA, V = 5V

●

0.8

OL

REG

CC

I

V

= 0.8V, V = 5V

7

2

REG

CC

V

= 5V

IH

IL

CC

0.8

1

CC

I

t

= V

CC

0.1

1

IN

ON

SHDN

Turn-On Time

I

= 10mA

OUT

V

Output Regulation

(LTC1550CGN/LTC1550IGN)

2.7V ≤ V ≤ 6.5V, 0 ≤ I

≤ 5mA

≤ 10mA

≤ 20mA

●

–1.575

–1.5

–1.425

V

OUT

CC

OUT

2.8V ≤ V ≤ 6.5V, 0 ≤ I

CC

3.5V ≤ V ≤ 6.5V, 0 ≤ I

CC

V

Output Regulation

(LTC1550CGN/LTC1550IGN)

2.7V ≤ V ≤ 6.5V, 0 ≤ I

≤ 5mA

≤ 10mA

●

–2.1

–2.0

–1.9

V

OUT

CC

OUT

3.1V ≤ V ≤ 6.5V, 0 ≤ I

CC

3.75V ≤ V ≤ 6.5V, 0 ≤ I

≤ 20mA

CC

OUT

2

LTC1550/LTC1551

ELECTRICAL CHARACTERISTICS

V_CC= 4.5V to 6.5V, C1 = C2 = 0.1µF, C_OUT= 10µF, T_A= 25°C unless otherwise specified. (Note 3)

SYMBOL PARAMETER CONDITIONS

3.05V ≤ V ≤ 6.5V, 0 ≤ I

MIN

TYP

MAX

UNITS

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

Output Regulation

≤ 5mA

●

–2.625

–3.15

–3.675

–4.3

–4.725

–4.3

–2.5

–3.0

–3.5

–4.1

–4.5

–4.1

–2.375

–2.85

–3.325

–3.9

–4.275

–3.9

V

CC

OUT

(LTC1550CGN/LTC1550IGN)

3.45V ≤ V ≤ 6.5V, 0 ≤ I

≤ 10mA

≤ 20mA

CC

4.1V ≤ V ≤ 6.5V, 0 ≤ I

CC

OUT

Output Regulation

(LTC1550CGN/LTC1550IGN)

3.45V ≤ V ≤ 6.5V, 0 ≤ I

≤ 5mA

≤ 10mA

●

CC

OUT

3.85V ≤ V ≤ 6.5V, 0 ≤ I

CC

4.5V ≤ V ≤ 6.5V, 0 ≤ I

≤ 20mA

CC

OUT

Output Regulation

(LTC1550CGN/LTC1550IGN)

3.9V ≤ V ≤ 6.5V, 0 ≤ I

≤ 5mA

≤ 10mA

●

CC

OUT

4.2V ≤ V ≤ 6.5V, 0 ≤ I

CC

OUT

4.85V ≤ V ≤ 6.5V, 0 ≤ I

≤ 20mA

CC

OUT

Output Regulation

(LTC1550CGN/LTC1550IGN)

4.5V ≤ V ≤ 6.5V, 0 ≤ I

≤ 5mA

OUT

●

CC

4.75V ≤ V ≤ 6.5V, 0 ≤ I

≤ 10mA

≤ 20mA

CC

OUT

5.35V ≤ V ≤ 6.5V, 0 ≤ I

CC

Output Regulation

(LTC1550CGN/LTC1550IGN)

4.8V ≤ V ≤ 6.5V, 0 ≤ I

≤ 5mA

≤ 10mA

≤ 20mA

●

CC

OUT

5.1V ≤ V ≤ 6.5V, 0 ≤ I

CC

5.7V ≤ V ≤ 6.5V, 0 ≤ I

CC

Output Regulation

(LTC1550CS8-4.1/LTC1551CS8-4.1)

4.5V ≤ V ≤ 6.5V, 0 ≤ I

≤ 5mA

●

CC

OUT

4.75V ≤ V ≤ 6.5V, 0 ≤ I

≤ 10mA

≤ 20mA

CC

OUT

5.35V ≤ V ≤ 6.5V, 0 ≤ I

CC

I

Output Short-Circuit Current

V

OUT

V

OUT

= 0V, V = 5V

●

50

80

150

200

mA

SC

CC

= 0V, V = 6.5V

CC

V

Output Ripple Voltage

1

mV

RIPPLE

The

●

denotes specifications which apply over the specified

Note 3: C-grade device specifications are guaranteed over the 0°C to 70°C

temperature range. In addition, C-grade device specifications are assured

over the –40°C to 85°C temperature range by design or correlation, but

are not production tested.

temperature range.

Note 1: Absolute Maximum Ratings are those values beyond which the life

of a device may be impaired.

Note 2: All currents into device pins are positive; all currents out of device

pins are negative. All voltages are referenced to ground unless otherwise

specified. All typicals are given at T = 25°C.

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TYPICAL PERFORMANCE CHARACTERISTICS

Oscillator Frequency

vs Temperature

Output Voltage vs Output Current

(LTC1550CS8-4.1/LTC1551CS8-4.1)

Supply Current vs Temperature

975

925

875

825

–3.0

–3.2

6.0

5.5

T

= 25°C

V

= –4.1V

V

= –4.1V

A

OUT

= 5V

OUT

CC

5.0

–3.4

–3.6

–3.8

–4.0

–4.2

V

= 4.5V

CC

4.5

4.0

V

= 5V

CC

V

CC

= 5V

775

725

675

3.5

3.0

V

CC

= 6.5V

35

–5

TEMPERATURE (˚C)

75

95

0

10

15

20

25

30

–45 –25

15

55

5

–45 –25

–5

15

35

55

75

95

OUTPUT CURRENT (mA)

TEMPERATURE (°C)

LTC1550/51 G01

LTC1550/51 G03

LTC1550/51 G02

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LTC1550/LTC1551

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TYPICAL PERFORMANCE CHARACTERISTICS

Maximum Output Current

vs Supply Voltage

Start-Up Time vs Supply Voltage

Startup Time (LTC1550 Shown)

50

45

40

35

30

25

20

15

10

5

2.0

1.8

1.6

1.4

T

V

R

= 25°C

OUT

= 390Ω

T

A

= 25°C

A

= –4.1V

5V

SHDN

L

0V

1.2

1.0

V_OUT

–4.1V

0.8

0.6

0.4

0.2ms/DIV

LTC1550/51 • G06

0

4.50

5.50

6.00 6.25

4.75 5.00

5.75

5.25 5.50

4.75 5.00 5.25

5.75

6.50

4.50

6.00 6.25 6.50

SUPPLY VOLTAGE (V)

LTC1550/51 • TPC04

LTC1550/51 G05

Load Transient Response

(See Figure 2, V_CC= 5V)

Line Transient Response

(See Figure 2, I_L= 10mA)

Minimum Required V_CCvs

V_OUTand I_OUT

6.0

5.6

5.2

4.8

4.4

4.0

3.6

3.2

2.8

2.4

2.0

5mV/DIV

V_OUT

AC COUPLED

I

= 20mA

OUT

10mA

I_OUT

5.5V

V_CC

0mA

5V

I

= 10mA

–1

OUT

I

= 5mA

–3

OUT

1ms/DIV

2ms/DIV

LTC1550/51 • G07

LTC1550/51 • G08

–5

–4

–2

0

OUTPUT VOLTAGE (V)

LTC1550/51 • G08.5

Output Spectrum

(*See Typical Application)

Spot Noise

(*See Typical Application)

Output Spectrum

(See Figure 2, C_OUT= 10µF)

90

80

70

60

50

40

30

20

10

0

90

80

70

60

50

40

30

20

10

0

10

V

L

C

= 5V

CC

I

= 5mA

= 4.7µF

IN

= 10µF

OUT

= 0.1µF

L

1

0.1

–10

0.01

100k

1M

10M

100k

1M

10M

1

10

100

FREQUENCY (Hz)

FREQUENCY (kHz)

LT1550/51 • G09

LT1550/51 • G11

LTC1550/51 • G10

* On first page of data sheet.

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LTC1550/LTC1551

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TYPICAL PERFORMANCE CHARACTERISTICS

Spot Noise

Output Spectrum

Spot Noise

(See Figure 2, C_OUT= 22µF)

(See Figure 2, C_OUT= 10µF)

(See Figure 2, C_OUT= 22µF)

90

80

70

60

50

40

30

20

10

0

10

V

I

= 5V

V

I

C

= 5V

CC

V

I

C

= 5V

CC

L

IN

= 5mA

L

= 5mA

L

IN

OUT

= 0.1µF

C

= 4.7µF

= 10µF

4.7µF

IN

OUT

= 0.1µF

= 4.7µF

= 22µF

OUT

= 0.1µF

L

1

0.1

–10

0.01

100k

1M

10M

1

10

100

1

10

100

FREQUENCY (Hz)

FREQUENCY (kHz)

LT1550/51 • G13

LTC1550/51 • G12

LTC1550/51 • G14

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PIN FUNCTIONS

SHDN: Shutdown (TTL Compatible). This pin is active low

(SHDN) for the LTC1550 and active high (SHDN) for the

LTC1551. When this pin is at V_CC(GND for LTC1551), the

LTC1550 operates normally. When SHDN is pulled low

(high for LTC1551), the LTC1550 enters shutdown mode.

Inshutdown, thechargepumpstops, theoutputcollapses

to 0V, and the quiescent current drops typically to 0.2µA.

regulator loop stability. At least 10µF is recommended to

provide specified output ripple. An additional 0.1µF low

ESR capacitor is recommended to minimize high fre-

quency spikes at the output.

C1^–: C1 Negative Input. Connect a 0.1µF capacitor from

C1⁺to C1^–.

GND: Ground. Connect to a low impedance ground. A

V_CC:PowerSupply. V_CCrequiresaninputvoltagebetween

4.5V and 6.5V for the fixed voltage LTC1550CS8-4.1/

LTC1551CS8-4.1. The adjustable voltage LTC1550CGN/

LTC1550IGN operates with a VCC range of 2.7V to 6.5V.

Output voltage and output load current conditions depend

on the VCC supply voltage. Consult the Electrical Charac-

teristicstable and TypicalPerformance Characteristics for

guaranteed test points. The difference between the input

voltage and output should never be set to exceed 14V or

damage to the chip may occur. V_CCmust be bypassed to

PGND (GND for 8-pin packages) with at least a 0.1µF

capacitor placed in close proximity to the chip. A 4.7µF or

larger bypass capacitor is recommended to minimize

noise and ripple at the output.

ground plane will help minimize regulation errors.

CP_OUT: Negative Charge Pump Output. This pin requires a

0.1µF storage capacitor to ground.

SENSE: Connect to V_OUT. The LTC1550/LTC1551 internal

regulator uses this pin to sense the output voltage. For

optimum regulation, SENSE should be connected close to

the output load.

SSOP PACKAGE ONLY

PGND:PowerGround.Connecttoalowimpedanceground.

PGND should be connected to the same potential as

AGND.

C1⁺: C1PositiveInput.Connecta0.1µFcapacitorbetween

AGND: Analog Ground. Connect to a low impedance

ground. AGND should be connected to a ground plane to

minimize regulation errors.

C1⁺and C1^–.

V_OUT: NegativeVoltageOutput.Thispinmustbebypassed

to ground with a 4.7µF or larger capacitor to ensure

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LTC1550/LTC1551

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PIN FUNCTIONS

REG: This is an open-drain output that pulls low when the

outputvoltageiswithin5%ofthesetvalue.Itwillsink7mA

to ground with a 5V supply. The external circuitry must

provide a pull-up or REG will not swing high. The voltage

at REG may exceed V_CCand can be pulled up to 12V above

ground without damage.

divider string from AGND to V_OUTwith the divided tap

connected to ADJ. Note that the resistor string needs to be

connected“upside-down”fromatraditionalnegativeregu-

lator. See the Applications Information section for hook-

up details.

NC: No Internal Connection.

ADJ: For adjustable versions only, this is the feedback

point for the external resistor divider string. Connect a

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BLOCK DIAGRAM

+

C

CP

C

OUT

V

CP

CC

OUT

S1

LINEAR

REGULATOR

V

OUT

S4

+

C1

CLK

900kHz

C1

–

S2

C1

+

–

**

S3

ADJ

REG

CHARGE

PUMP

*SHDN

+

–

60mV

1.18V

SENSE

COMP2

1.24V

*SHDN FOR LTC1550, SHDN FOR LTC1551

** FIXED OUTPUT VERSIONS ONLY

1550/51 BD

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APPLICATIONS INFORMATION

Consult the graph provided in the Typical Performance

Characteristics section and the Electrical Characteristics

table for guaranteed test points. The LTC1550/LTC1551

are ideal for use as bias voltage generators for GaAs

transmitter FETs in portable RF and cellular telephone

applications. The LTC1550 features an active-low

Shutdown pin (SHDN) that drops quiescent current to

below 1µA. The LTC1551 is identical to the LTC1550,

OVERVIEW

The LTC1550/LTC1551 are switched capacitor, inverting

charge pumps with internal linear post-regulators. The

LTC1550CS8/LTC1551CS8providearegulated,lowripple

–4.1V output at up to 10mA load current from a single 5V

supply. The LTC1550CGN provides a regulated, low ripple

adjustable output. Output load current for the adjustable

version depends on the input/output voltage combination.

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LTC1550/LTC1551

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APPLICATIONS INFORMATION

except that the Shutdown pin is active-high (SHDN). All

members of the LTC1550 family feature a 900kHz charge

pump frequency. The LTC1550/ LTC1551 come standard

with fixed –4.1V output voltages and the LTC1550 is

available with an adjustable output voltage. Both devices

canbeconfiguredwithotherfixedoutputvoltages;contact

Linear Technology for more information.

6, 7

PGND, AGND

R1

R2

10

ADJ

LTC1550

4, 11

R1 + R2

R2

V

, SENSE

OUT

V

= –1.24V

OUT

(

)

LTC1550/51 • F02

Figure 1. External Resistor Connections

The LTC1550 consists of two major blocks (see Block

Diagram): an inverting charge pump and a negative linear

regulator. The charge pump uses two external capacitors,

C1 and C_CPto generate a negative voltage at CP_OUT. It

operates by charging and discharging C1 on alternate

phases of the internal 900kHz clock. C1 is initially charged

to V_CCthrough switches S1 and S3. When the internal

clockchangesphase,S1andS3openandS2andS4close,

shorting the positive side of C1 to ground. This forces the

negativesideofC1belowground,andchargeistransferred

to C_CPthrough S4. As this cycle repeats, the magnitude of

the negative voltage approaches V_CC. The 900kHz internal

clock frequency helps keep noise out of 400kHz to 600kHz

IF bands commonly used by portable radio frequency

systems and reduces the size of the external capacitors

required.Mostapplicationscanusestandard0.1µFceramic

capacitors for C1 and C_CP. Increasing C1 and C_CPbeyond

0.1µF has little effect on the output ripple or the output

current capacity of the LTC1550/LTC1551.

Adjustable Hook-Up

The LTC1550CGN is available in an adjustable output

version in a 16-pin SSOP package. The output voltage is

set with a resistor divider from GND to SENSE/V_OUT

(Figure 1). Note that the internal reference and the internal

feedback amplifier are set up as a positive-output regula-

tor referenced to the SENSE pin, not a negative regulator

referenced to ground. The output resistor divider must be

set to provide a 1.24V at the ADJ pin with respect to V_OUT

.

For example, a –3V output would require a 13k resistor

from GND to ADJ, and a 9.1k resistor to SENSE/V_OUT. If,

afterconnectingthedividerresistors, theoutputvoltageis

not what you expected, try swapping them.

CAPACITOR SELECTION

The LTC1550/LTC1551 requires four external capacitors:

aninputbypasscapacitor, two0.1µFchargepumpcapaci-

tors and an output filter capacitor. The overall behavior of

the LTC1550/LTC1551 is strongly affected by the capaci-

tors used. In particular, the output capacitor has a signifi-

cant effect on the output ripple and noise performance.

Proper capacitor selection is critical for optimum perfor-

mance of the LTC1550/LTC1551.

The negative voltage at CP_OUTsupplies the input to the

negative regulator block. This block consists of an

N-channel MOSFET pass device and a feedback amplifier

that monitors the output voltage and compares it to the

internal reference. The regulated output appears at the

V_OUTpin. The regulation loop is optimized for fast tran-

sient response, enabling it to remove most of the switch-

ing artifacts present at the CP_OUTpin. Output ripple is

typically below 1mV_P-Pwith output loads between 0mA

and 10mA. The output voltage is set to –4.1V by a pair of

internaldividerresistors. TheN-channelpassdevicemini-

mizes dropout, allowing the output to remain in regulation

with supply voltages as low as 4.5V. An output capacitor

of at least 4.7µF from V_OUTto ground is required to keep

the regulator loop stable; for optimum stability and mini-

mum output ripple, at least 10µF is recommended.

Output Ripple vs Output Capacitor

Figure 3 shows the effect of using different output capaci-

tor values on LTC1550/LTC1551 output ripple. These

curves are taken using the circuit in Figure 2, with

C_IN= 4.7µF and I_LOAD= 5mA. The upper curve shows the

performancewithastandardtantalumcapacitoraloneand

the lower curve shows the tantalum capacitor in parallel

with a 0.1µF ceramic capacitor. As a general rule, larger

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LTC1550/LTC1551

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APPLICATIONS INFORMATION

millivolts under some conditions. A garden variety 0.1µF

ceramiccapacitorhassignificantlylowerimpedanceatthe

spike frequency than even a large tantalum capacitor, and

helps eliminate most of these left-over switching spikes

that the tantalum capacitor leaves behind. Figure 4 and 5

show scope photos of the output of Figure 3 with and

without the additional ceramic capacitor at the output.

output capacitors provide lower output ripple. To keep

ripplebelow1mV_P-P,10µForgreater,witha0.1µFceramic

capacitor in parallel, is required. At least 4.7µF is required

at the output under all conditions to guarantee loop

stability.

Figure 3 shows a marked decrease in peak-to-peak output

ripple when a 0.1µF ceramic capacitor added in parallel

with the tantalum output capacitor. The additional ripple

with the tantalum output capacitor alone is mostly very

high order harmonics of the 900kHz clock, which appear

as sharp "spikes" at the output. The energy in these spikes

is very small and they do not contribute to the RMS output

voltage, but their peak-to-peak amplitude can be several

A series RC or LC filter can reduce high frequency output

noise even further. Due to the high 900kHz switching

frequency, not much R or L is required; a ferrite bead or a

relatively long PC board trace in series with 0.1µF ceramic

capacitor will usually keep the output ripple well below

1mV_P-P. The cover page shows an example of an ultralow

8

V

T

= 6V

CC

A

IN

= 25°C

7

6

5

4

3

2

1

0

C

= 4.7µF

WITHOUT 0.1µF

1

2

8

7

V

CC

SHDN

SENSE

CP

V

CC

OUT

+

C

IN

CP

LTC1551

4.7µF

0.1µF

3

4

6

+

C1

GND

WITH 0.1µF

5

–

V

C1

OUT

V

OUT

–4.1V

1

10

100

C

OUT

L

OUTPUT CAPACITANCE (µF)

+

10µF

0.1µF*

C1

0.1µF

LTC1550/51 • F04

*C IS OPTIONAL

L

1550/51 F03

Figure 3. Output Ripple vs Output Capacitance

Figure 2. Output Ripple Test Circuit

V_OUT

AC COUPLE

2mV/DIV

V_OUT

AC COUPLE

5mV/DIV

5µs/DIV

LTC1550/51 • F03

10µs/DIV

LTC1550/51 • F04

Figure 4. Output Ripple with 10µF Tantalum Capacitor

Figure 5. Output Ripple with 10µF Tantalum

Capacitor Paralleled with 0.1µF Ceramic Capacitor

8

LTC1550/LTC1551

U

W U U

APPLICATIONS INFORMATION

noise –4.1V generator which uses a ferrite bead output

filter to achieve better than 1mV_P-Pnoise and output

ripple. The corresponding spectrum and spot noise plots

for this circuit are shown in the Typical Performance

Characteristics section.

switches,causingtheoutputlinearregulatortomomentarily

stop regulating. C_INshould be mounted as close to the

LTC1550/LTC1551 as possible and its value should be

significantly larger than C1. Tantalum capacitors with low

ESR generally provide adequate performance. Figure 6

shows the LTC1550/LTC1551 peak-to-peak output ripple

vsC_IN, takenusingthetestcircuitinFigure2withI_LOADset

at 5mA. C_OUTis a 10µF in parallel with a 0.1µF ceramic

capacitor.

Output Ripple vs Input Bypass Capacitor

The input bypass capacitor (C_IN) can also have a fairly

significant impact on the output ripple. C_INprovides most

of the LTC1550/LTC1551’s supply current while it is

chargingtheflyingcapacitor(C1).Inadequateinputbypass

can cause the V_CCsupply to dip when the charge pump

A 4.7µF tantalum capacitor at V_CCgenerally provides

adequate output ripple performance for most applica-

tions.

8

V

A

C

= 6V

CC

7

6

5

4

3

2

1

0

T

= 25°C

= 10µF

OUT

0.1

1

10

100

INPUT CAPACITANCE (µF)

LTC1550/51 • F07

Figure 6. Output Ripple vs Input Bypass Capacitance

U

TYPICAL APPLICATION

–4.1V Output GaAs FET Bias Generator

1

2

8

7

SHDN

SENSE

CP

4.5V ≤ V ≤ 6.5V

CC

V

CC

OUT

+

C

CP

0.1µF

C

IN

4.7µF

LTC1550

3

4

6

+

C1

GND

5

–

V

C1

OUT

–4.1V BIAS

C

L

0.1µF

OUT

GaAs

TRANSMITTER

+

10µF

C1

0.1µF

1550/51 TA02

9

LTC1550/LTC1551

U

PACKAGE DESCRIPTION ^{Dimensions in inches (millimeters) unless otherwise noted.}

GN Package

16-Lead Plastic SSOP (Narrow 0.150)

(LTC DWG # 05-08-1641)

0.189 – 0.196*

(4.801 – 4.978)

16 15 14 13 12 11 10

9

0.229 – 0.244

(5.817 – 6.198)

0.150 – 0.157**

(3.810 – 3.988)

1

2

3

4

5

6

7

8

0.015 ± 0.004

(0.38 ± 0.10)

× 45°

0.053 – 0.069

(1.351 – 1.748)

0.004 – 0.009

(0.102 – 0.249)

0.0075 – 0.0098

(0.191 – 0.249)

0° – 8° TYP

0.016 – 0.050

(0.406 – 1.270)

0.008 – 0.012

(0.203 – 0.305)

0.025

(0.635)

BSC

*

DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH

SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

GN16 (SSOP) 0895

** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD

FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

10

LTC1550/LTC1551

U

PACKAGE DESCRIPTION

Dimensions in inches (millimeters) unless otherwise noted.

S8 Package

8-Lead Plastic Small Outline (Narrow 0.150)

(LTC DWG # 05-08-1610)

0.189 – 0.197*

(4.801 – 5.004)

7

5

8

6

0.150 – 0.157**

(3.810 – 3.988)

0.228 – 0.244

(5.791 – 6.197)

1

3

4

2

0.010 – 0.020

(0.254 – 0.508)

× 45°

0.053 – 0.069

(1.346 – 1.752)

0.004 – 0.010

(0.101 – 0.254)

0.008 – 0.010

(0.203 – 0.254)

0°– 8° TYP

0.016 – 0.050

0.406 – 1.270

0.050

(1.270)

TYP

0.014 – 0.019

(0.355 – 0.483)

*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH

SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

SO8 0996

**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD

FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.

11

LTC1550/LTC1551

TYPICAL APPLICATION

U

< 1mV_P-PRipple, –4.1V Output GaAs FET Bias Generator

1

2

8

7

SHDN

SENSE

CP

4.5V ≤ V ≤ 6.5V

CC

V

CC

OUT

+

C

CP

C

IN

LTC1550

0.1µF

4.7µF

3

4

6

+

C1

GND

5

–

V

C1

OUT

FERRITE BEAD

–4.1V

C

L

0.1µF

OUT

GaAs

TRANSMITTER

+

10µF

C1

0.1µF

1550/51 TA03

RELATED PARTS

PART NUMBER

LT^®1054

DESCRIPTION

COMMENTS

Switched-Capacitor Voltage Converter with Regulator

Switched-Capacitor Regulated Voltage Inverter

100mA Switched-Capacitor Converter

Selectable Fixed Output Voltages

LTC1261

LTC1429

Clock-Synchronized Switched-Capacitor Voltage Inverter

Synchronizable Up to 2MHz System Clock

15501fa LT/TP 0897 REV A 4K • PRINTED IN USA

12 ^{Linear Technology Corporation}

●

1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900

●

FAX: (408) 434-0507 TELEX: 499-3977 www.linear-tech.com

LINEAR TECHNOLOGY CORPORATION 1996


型号：	LTC1550LCGN#PBF
厂家：	Linear
描述：	LTC1550L - Low Noise, Switched Capacitor Regulated Voltage Inverters; Package: SSOP; Pins: 16; Temperature Range: 0°C to 70°C 开关高压
文件：	总12页 (文件大小：323K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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