IC VOLT INVERT SW-CAP ADJ 14SOIC

LTC1261CS#PBF

Manufacturer Part NumberLTC1261CS#PBF
DescriptionIC VOLT INVERT SW-CAP ADJ 14SOIC
ManufacturerLinear Technology
TypeSwitched Capacitor (Charge Pump), Inverting
LTC1261CS#PBF datasheet
 

Specifications of LTC1261CS#PBF

Internal Switch(s)YesSynchronous RectifierNo
Number Of Outputs1Voltage - Output-1.25 ~ -8 V
Current - Output15mAFrequency - Switching550kHz
Voltage - Input3 ~ 8 VOperating Temperature0°C ~ 70°C
Mounting TypeSurface MountPackage / Case14-SOIC (3.9mm Width), 14-SOL
Lead Free Status / RoHS StatusLead free / RoHS CompliantPower - Output-
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FEATURE
S
Regulated Negative Voltage from a
Single Positive Supply
Can Provide Regulated – 5V from a 3V Supply
REG Pin Indicates Output is in Regulation
Low Output Ripple: 5mV Typ
Supply Current: 600 A Typ
Shutdown Mode Drops Supply Current to 5 A
Up to 15mA Output Current
Adjustable or Fixed Output Voltages
Requires Only Three or Four External Capacitors
Available in SO-8 Packages
U
O
PPLICATI
A
S
GaAs FET Bias Generators
Negative Supply Generators
Battery-Powered Systems
Single Supply Applications
U
TYPICAL
APPLICATION
– 4V Generator with Power Valid
5V
1
8
5V
V
SHDN
CC
10k
2
7
+
C1
REG
C1
C2
LTC1261-4
1 F
0.1 F
3
6
C1
OUT
4
5
GND
COMP
*OPTIONAL
Regulated Voltage Inverter
D
ESCRIPTIO
®
The LTC
designed to provide a regulated negative voltage from a
single positive supply. The LTC1261CS 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 LTC1261CS to be configured for output volt-
ages of – 3.5V, – 4V, – 4.5V or – 5V with no external
components. The LTC1261CS8 is optimized for applica-
tions which use a 5V or higher supply or which require
low output voltages. It requires a single external 0.1 F
capacitor and provides adjustable and fixed output voltage
options in 8-pin SO packages. The LTC1261CS requires
one or two external 0.1 F 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 LTC1261 will supply up to 12mA
output current with guaranteed output regulation of 5%.
The LTC1261 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. Quiescent current
is typically 600 A when operating and 5 A in shutdown.
The LTC1261 is available in a 14-pin narrow body SO
package and an 8-pin SO package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Waveforms for – 4V Generator with Power Valid
OUT
– 4V
POWER VALID
SHDN
V
= –4V
OUT
AT 10mA
C4
3.3 F
+
POWER VALID
C3*
100pF
LTC1261 • TA01
LTC1261
Switched Capacitor
U
1261 is a switched-capacitor voltage inverter
0V
5V
0V
5V
0V
0.2mS/DIV
LTC1261 • TAO2
1

LTC1261CS#PBF Summary of contents

  • Page 1

    ... Output ripple is typically as low as 5mV. Quiescent current is typically 600 A when operating and shutdown. The LTC1261 is available in a 14-pin narrow body SO package and an 8-pin SO package. , LTC and LT are registered trademarks of Linear Technology Corporation. Waveforms for – 4V Generator with Power Valid OUT – 4V ...

  • Page 2

    LTC1261 BSOLUTE (Note 1) Supply Voltage (Note 2)............................................ 9V Output Voltage (Note 5) .............................. 0.3V to – 9V Total Voltage (Note 2) ........................ 12V CC OUT Input Voltage SHDN Pin ...

  • Page 3

    ELECTRICAL C HARA TERISTICS C Doubler Mode 10 0 (Note 4 SYMBOL PARAMETER CONDITIONS (Note 2) V Output Regulation – 1.24V V OUT (Note 2) – 1.24V V – ...

  • Page 4

    LTC1261 W U TYPICAL PERFORMANCE CHARACTERISTICS Output Voltage vs Output Current –3 –3.6 A –3.7 –3 –3.9 DOUBLER MODE –4 3.3V CC –4.1 TRIPLER MODE –4.2 –4.3 –4.4 –4.5 0 ...

  • Page 5

    PIN FUNCTIONS Pin numbers are shown as (LTC1261CS/LTC1261CS8). NC (Pin 1/NA): No Internal Connection (Pin 2/ Pin 2): C1 Positive Input. Connect a 0 – capacitor between C1 and C1 . With the ...

  • Page 6

    LTC1261 U U APPLICATIONS INFORMATION MODES OF OPERATION The LTC1261 uses a charge pump to generate a negative output voltage that can be regulated to a value either higher or lower than the original input voltage. It has two modes ...

  • Page 7

    U U APPLICATIONS INFORMATION CLK 550kHz COMP 1 – V REF The output voltage is monitored by COMP1 which com- pares a divided replica of the output at ADJ (COMP for fixed output parts) to the ...

  • Page 8

    LTC1261 U U APPLICATIONS INFORMATION OUTPUT RIPPLE Output ripple in the LTC1261 comes from two sources; voltage droop at the output capacitor between clocks and frequency response of the regulation loop. Voltage droop is easy to calculate. With a typical ...

  • Page 9

    U U APPLICATIONS INFORMATION OUT 0.1 F LTC1261CS8 – C1 COMP + GND 100pF 4 Figure 4. Output Filter Cuts Ripple Below 3mV CAPACITOR SELECTION Capacitor Sizing The performance ...

  • Page 10

    LTC1261 U U APPLICATIONS INFORMATION pump from going into very high frequency oscillation under such conditions but it also creates an output error as the feedback loop regulates based on the top of the spike, not the average value of ...

  • Page 11

    ... The LTC1261 can be internally configured with nonstand- ard fixed output voltages. Contact the Linear Technology Marketing Department for details. N 3.3V Input, – 4.5V Output GaAs FET Bias Generator ...

  • Page 12

    LTC1261 U TYPICAL APPLICATIONS V BAT SHUTDOWN 0 8.4V BAT (7 NiCd CELLS) SHUTDOWN 1 F 0.1 F 1mV Ripple, 5V Input, – 4V Output GaAs FET Bias Generator V BAT SHUTDOWN 5V 1 ...

  • Page 13

    U TYPICAL APPLICATIONS High Supply Voltage, – 5V Output GaAs FET Bias Generator 8V V 12V BAT SHUTDOWN 0.1 F 0.1 F Low Output Voltage Generator 100pF ADJ 0.1 F ...

  • Page 14

    LTC1261 U TYPICAL APPLICATIONS This circuit uses the LTC1261CS8 to generate a – 1.24V output at 20mA. Attached to this output is a 312 resistor to make the current/voltage conversion. 4mA through 312 generates 1.24V, giving a net 0V output. ...

  • Page 15

    ... 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- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. ...

  • Page 16

    ... GaAs FET Bias with Linear Regulator 1mV Ripple GaAs FET Bias 0.4V Dropout Voltage at 150mA, Low Noise, Switched Capacitor Regulated Voltage Inverter –0.5V BIAS 5.5% GaAs TRANSMITTER 3.3 F LTC1261 • TA08 1261fa LT/TP 0198 REV A 4K • PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 1994 ...