Linear Technology LTC1429 Datasheet

FEATURES

LTC1429

Clock-Synchronized

Switched Capacitor

Regulated Voltage Inverter

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DESCRIPTION

■

Regulated Negative Voltage from a Single
Positive Supply

■

External Clock for Synchronization in Noise
Sensitive Systems

■

REG Output Indicates Output is in Regulation

■

Low Output Ripple: 5mV Typ

■

Can Provide Regulated –5V from a 3V Supply

■

Supply Current: 600µA Typ

■

Shutdown Mode Drops Supply Current to 0.2µA

■

Up to 12mA Output Current

■

Adjustable or Fixed Output Voltages

■

Requires Only Three or Four External Caps

■

Output Regulation: 5%

■

Available in SO-8 Packages

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APPLICATIONS

■

GaAs FET Bias Generators

■

Negative Supply Generators

■

Battery Powered Systems

■

Single Supply Applications

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





The LTC®1429 is a switched-capacitor voltage inverter de­signed to provide a regulated negative voltage from a single
positive supply and permits clock synchronization in noise
sensitive systems. The LTC1429CS operates from a single 3V
to 8V supply and provides an adjustable output voltage from
–1.25V to –8V. An on-chip resistor string allows the
LTC1429CS to be configured for output voltages of –3.5V,
–4V, –4.5V or – 5V. The LTC1429CS8 is optimized for
applications which require a fixed –4V output from a 5V
supply and requires only a single external 0.1µF flying
capacitor. The LTC1429CS requires one or two external

0.1µF capacitors, depending on input voltage. Both versions
require additional external input and output bypass capaci­tors. An optional compensation capacitor at ADJ/COMP can
be used to reduce the output voltage ripple.

Each version of the LTC1429 guarantees output regulation of
5%. The LTC1429 includes an open-drain REG output which
pulls low when the output is within 5% of the set value. Output
ripple is typically as low as 5mV. The LTC1429 requires an
external clock applied to the SYNC/SD for normal operation
and consumes a typical quiescent current of 600µ A. Holding
the SYNC/SD either high or low brings the device into
shutdown and the supply current drops to 0.2µ A. For appli­cations which don’t have a clock signal available, the LTC1261
provides the same functionality with an internal oscillator. For
applications which require output ripple below 1mV, see the
LTC1550/LTC1551. The LTC1429CS is available in a 14-pin
SO package and the LTC1429CS8 is available in an 8-pin SO
package.

TYPICAL APPLICATION

–4V Generator with Power Valid

5V

0.1µF

C1

*OPTIONAL

0.1µF

1

V

2

C2

C1

3

C1

4

GND

SYNC/SD

CC

+

LTC1429-4CS8

–

REG

OUT

COMP

8

7

6

5

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*C3 

0.001µF

10k

5V
POWER VALID

V

+

= –4V AT 10mA

OUT

C4

3.3µF

LTC1429 • TA01

Waveforms for –4V Generator with Power Valid

0V

V

OUT

–4V

POWER VALID

SYNC/SD

5V
0V
5V
0V

0.2ms/DIV

LTC1429 • TA02

1

LTC1429

TOP VIEW

S PACKAGE

14-LEAD PLASTIC SO

1
2
3
4
5
6
7



14
13
12
11
10

9
8



NC

C1

+



C1

–



C2

+



C2

–



GND

R0




V

CC

SYNC/SD
REG
OUT
ADJ
R

ADJ



R1

WW

W

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ABSOLUTE MAXIMUM RATINGS

(Note 1)

Supply Voltage (Note 2)............................................. 9V

Output Voltage.............................................0.3V to –9V

Total Voltage, VCC to V

(Note 2) ......................... 12V

OUT

Input Voltage (SYNC/SD Pin) ...... –0.3V to (VCC + 0.3V)

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

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PACKAGE/ORDER INFORMATION

ORDER PART

NUMBER

LTC1429CS8-4*

S8 PART MARKING

14294

V

1



CC

+

C1



2

–

C1



3

GND

4

8-LEAD PLASTIC SO

TOP VIEW

S8 PACKAGE

8

7

6

5

SYNC/SD
REG
OUT
COMP

Input Voltage (ADJ, RO-1, R

.....................................(V

)

ADJ

– 0.3V) to (V

OUT

Output Short Circuit Duration .......................... Indefinite

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

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

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

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ORDER PART

NUMBER

LTC1429CS

+ 0.3V)

CC

T

= 150°C, θJA = 150°C/W

JMAX

T

= 150°C, θJA = 110°C/W

JMAX

Consult factory for Industrial and Military grade parts. *Contact factory for other output voltages or 8-pin adjustable parts.

ELECTRICAL CHARACTERISTICS

VCC = 3V to 6.5V. C1 = C2 = 0.1µF (Note 4), C

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

REF

I

S

F

SYNC

P

EFF

V

OL

I

REG

I

ADJ

V

IH

V

IL

I

IN

T

ON

2

Reference Voltage ● 1.20 1.24 1.28 V
Supply Current VCC = 3.3V ● 600 1500 µA

Synchronous Clock Frequency (Note 8) VCC ≤ 5V 60 700 2000 kHz

Power Efficiency 65 %
REG Output Low Voltage I
REG Sink Current V

Adjust Pin Current V
SYNC/SD Input High Voltage VCC = 5V ● 2.0 V
SYNC/SD Input Low Voltage VCC = 5V ● 0.8 V
SYNC/SD Input Current V
Turn On Time I

= 3.3µF, F

OUT

= 700kHz with 50% duty cycle square wave, unless otherwise noted.

SYNC

LTC1429CS8/LTC1429CS

= 5V ● 600 1500 µA

V

CC

V

= VCC or GND ● 0.2 5 µA

SYNC/SD

VCC = 6.5V 100 700 2000 kHz

= 1mA ● 0.1 0.8 V

REG

= 0.8V, VCC = 3.3V ● 58 mA

REG

V

= 0.8V, VCC = 5V ● 815 mA

REG

= 1.24V (Note 5) ● 0.01 1 µA

ADJ

= VCC or GND ● ±1 µA

SYNC/SD

= 10mA 200 µs

OUT

LTC1429

SUPPLY VOLTAGE (V)

3.0

0

MAXIMUM OUTPUT CURRENT (mA)

5

15

20

25

6.56.0

45

LTC1429 • TPC03

10

3.5 4.0 4.5 5.0 5.5 7.0

30

35

40

V

OUT

= –4V ± 5%

T

A

= 25°C

TRIPLER MODE

DOUBLER MODE

ELECTRICAL CHARACTERISTICS

F

= 700kHz with 50% duty cycle square wave, unless otherwise noted.

SYNC

Tripler Mode,VCC = 3.3V, C1 = C2 = 0.1µF (Note 4), C

= 3.3µF,

OUT

LTC1429CS

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

∆V

OUT

Output Regulation –1.24V ≥ V

–4V ≥ V

ISCOutput Short Circuit Current V
V

RIP

Output Ripple Voltage I

= 0V ● 35 75 mA

OUT

= 5mA, V

OUT

Doubler Mode, VCC = 5V, C1 = 0.1µ F, C2 = 0 (Note 4), C

OUT

≥ –5V, 0 ≤ I

OUT

OUT

= 3.3µF, F

OUT

≥ –4V, 0 ≤ I

≤ 12mA ● 15 %

OUT

≤ 8mA ● 25 %

OUT

= –4V 5 mV

=700kHz with 50% duty cycle, unless otherwise noted.

SYNC

LTC1429CS8/LTC1429CS

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

∆V

OUT

V

OUT

I

SC

V

RIP

The ● denotes specifications which apply over the full operating
temperature range.

Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.

Note 2: Setting output to < –7V will exceed the total voltage maximum
rating with a 5V supply. With supplies higher than 4V the output should
never be set to exceed (V

Note 3: 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

Note 4: C1 = C2 = 0.1µF means the specifications apply to tripler mode
where V

Output Regulation – 1.24V ≥ V

Output Voltage V
Output Short Circuit Current V
Output Ripple Voltage I

– 12V).

CC

= 25°C.

A

– V

CC

= 3.3VCC (LTC1429CS only; the LTC1429CS8 cannot be

OUT

≥ –4V, 0 ≤ I

–4V ≥ V

OUT
OUT

OUT

OUT

≥ –4.5V, 0 ≤ I

OUT

Set to –4V, 0 ≤ I

OUT

= 0V ● 80 125 mA

= 5mA, V

= –4V 10 mV

OUT

≤ 10mA ● 15 %

OUT

≤ 10mA (Note 6) ● 25 %

OUT

≤ 10mA ● –3.80 –4.00 –4.20 V

connected in tripler mode), with C1 connected between C1
C2 connected between C2

– V

V

CC

= 2VCC; for the LTC1429CS, this means C1 connects from C1

OUT

to C2– with C1– and C2+ floating. For the LTC1429CS8 in doubler mode,
C1 connects from C1

+

and C2–. C2 = 0 implies doubler mode where

+

to C1– ; there are no C2 pins.

+

and C1– and

Note 5: Adjustable output parts only; does not apply to fixed output parts.
Note 6: For output voltages below –4.5V, the LTC1429 may reach 50%

duty cycle and fall out of regulation with heavy load or low input voltages.
Beyond this point, the output will follow the input with no regulation.

Note 7: LTC1429 will operate with square wave of 40% to 60% duty cycle.
For best performance, use a square wave with 50% duty cycle.

Note 8: Maximum frequency is not tested. Typical part can be used
beyond 2MHz.

+

TYPICAL PERFORMANCE CHARACTERISTICS

(See Test Circuits; Figure 1 for Doubler Mode, Figure 2 for Tripler Mode)

Output Voltage vs Output Current Output Voltage vs Supply Voltage

–4.10
–4.08
–4.06
–4.04

–4.00

–3.96

OUTPUT VOLTAGE (V)

– 3.94
–3.92

TA = 25°C

–4.02

–3.98

–3.90

0

VCC = 5V
DOUBLER MODE

213579

VCC = 3.3V
TRIPLER MODE

6

4

OUTPUT CURRENT (mA)

W

8

LTC1429 • TPC01

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Maximum Output Current vs
Supply Voltage

–4.08

3.0

TA = 25°C

3.5

4.0
SUPPLY VOLTAGE (V)

DOUBLER MODE

= 5mA

I

L

TRIPLER MODE

= 5mA

I

L

5.0

4.5

5.5

6.0

LTC1429 • TPC02

6.5

7.0

–4.07

–4.06

–4.05

–4.04

–4.03

OUTPUT VOLTAGE (V)

–4.02

–4.01

10

–4.00

3

LTC1429

INPUT FREQUENCY (kHz)

100

SUPPLY CURRENT (µA)

750

700

650

600

550

500

450

1000 2000 4000

LTC1429 • TPC06

TA = 25°C
I

LOAD

= 0mA

DOUBLER MODE
V

CC

= 5V

TRIPLER MODE
V

CC

= 3.3V

W

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TYPICAL PERFORMANCE CHARACTERISTICS

(See Test Circuits: Figure 1 for Doubler Mode, Figure 2 for Tripler Mode)

Supply Current vs Supply Voltage Supply Current vs Temperature

1000

SUPPLY CURRENT (µA)

900
800
700
600
500
400
300
200
100

V

= –4V

OUT

= 25°C

T

A

0

4.03.5 4.5 5.5 6.5 7.5

3.0

TRIPLER MODE

5.0

SUPPLY VOLTAGE (V)

DOUBLER MODE

6.0

7.0

LTC1429 • TPC04

8.0

800

700

600

500

400

300

SUPPLY CURRENT (µA)

200

100

V

CC

DOUBLER MODE

V

= –4V

OUT

0

10 20 40

0

= 5V

VCC= 3.3V
TRIPLER MODE

30

TEMPERATURE (˚C)

50 60 70

LTC1429 • TPC05

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PIN FUNCTIONS

Supply Current vs
Input Frequency

Pin numbers are shown as (LTC1429CS/LTC1429CS8).

NC (Pin 1/NA): No Internal Connection.

+

C1

(Pin 2/Pin 2): C1 Positive Input. Connect an 0.1µF

capacitor between C1+ and C1–. With the LTC1429CS in
doubler mode, connect a 0.1µF capacitor from C1+ to C2–.

–

C1

(Pin 3/Pin 3): C1 Negative Input. Connect a 0.1µF

capacitor from C1+ to C1–. With the LTC1429CS in doubler
mode only, C1– should float.

C2+ (Pin 4/NA): C2 Positive Input. In tripler mode, connect
a 0.1µF capacitor from C2+ to C2– . This pin is used with
the LTC1429CS in tripler mode only; in doubler mode, this
pin should float.

C2– (Pin 5/NA): C2 Negative Input. In tripler mode, con­nect a 0.1µ F capacitor from C2+ to C2–. In doubler mode,
connect a 0.1µF capacitor from C1+ to C2–.

GND (Pin 6/Pin 4): Ground. Connect to a low-impedance
ground. A ground plane will help to minimize regulation
errors.

R0 (Pin 7/NA): Internal Resistor String-1st Tap. See Table
3 in the Applications Information section for information
on internal resistor string pin connections vs output
voltage.

R1 (Pin 8/NA): Internal Resistor String-2nd Tap.

4

R

(Pin 9/NA): Internal Resistor String Output. Connect

ADJ

this pin to ADJ to use the internal resistor divider. See
Table 3 in the Applications Information section for infor­mation on internal resistor string pin connections vs
output voltage.

ADJ (COMP for fixed output versions) (Pin 10/Pin 5):

Output Adjust/Compensation. For adjustable parts, this
pin is used to set the output voltage. The output voltage
should be divided down with a resistor divider and fed
back to this pin to set the regulated output voltage. The
resistor divider can be external or the internal divider
string can be used if it can provide the required output
voltage. Typically the resistor string should draw ≥ 10µ A
from the output to minimize errors due to the bias current
at the adjust pin. Fixed output parts have the internal
resistor string connected to this pin inside the package;
the pin can be used to trim the output voltage if desired. It
can also be used as an optional feedback compensation
pin to reduce output ripple on both adjustable and fixed
output voltage parts. See the Applications Information
section for more on compensation and output ripple.

OUT (Pin 11/Pin 6): Negative Voltage Output. This pin
must be bypassed to ground with a 1.0µF or larger
capacitor; it must be at least 3.3µF to provide specified
output ripple. The size of the output capacitor has a strong