IC VOLT INVERT SW-CAP ADJ 14SOIC

LTC1261CS

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

Specifications of LTC1261CS

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 StatusContains lead / RoHS non-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 Summary of contents

  • Page 1

    ... The LTC1261CS operates from a single 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 higher supply or which require low output voltages ...

  • Page 2

    ... OUT LTC1261CS8-4.5 ADJ (COMP PART MARKING S8 PACKAGE 8-LEAD PLASTIC SO 1261 *FOR FIXED VERSIONS 12614 = 150 C, = 150 C/W JA 126145 ORDER PART TOP VIEW NUMBER SHDN LTC1261CS 3 12 REG 4 11 OUT 5 10 ADJ ADJ PACKAGE 14-LEAD PLASTIC SO = 150 C, = 110 C unless otherwise specified – ...

  • Page 3

    ... LTC1261CS8 cannot be CC OUT CC connected in tripler mode) with C1 connected between C1 + – C2 connected between C2 and implies doubler mode where V – for the LTC1261CS this means C1 connects from C1 CC OUT CC = 3.3 F unless otherwise specified. OUT – 4V 8mA OUT OUT – 4V 7mA OUT OUT – ...

  • Page 4

    ... V = –4V OUT 1000 900 DOUBLER MODE 800 V 700 CC TRIPLER MODE 600 500 –40 – TEMPERATURE (˚C) Tripler Mode ADJ 3 9 – ADJ LTC1261CS – –4V 5% OUT OUT GND 3 LTC1261 • TC02 7 LTC1261 • TPC03 = 3.3V 80 100 LTC1261 • TPC06 ...

  • Page 5

    ... C2 (Pin 4/NA): C2 Positive Input. In tripler mode con- + nect a 0.1 F capacitor from with the LTC1261CS in tripler mode only; in doubler mode this pin should float. – C2 (Pin 5/NA): C2 Negative Input. In tripler mode connect a 0.1 F capacitor from C2 mode connect a 0.1 F capacitor from C1 GND (Pin 6/Pin 4): Ground ...

  • Page 6

    ... C1 and C2 pins. C1 floating (Figure 1b). Tripler Mode The LTC1261CS can be used in a tripler mode which can generate negative output voltages up to twice the supply voltage. The total voltage between the V can three times V . For example, tripler mode can S be used to generate – 5V from a single positive 3.3V supply ...

  • Page 7

    ... REG output will stay low. LTC1261 OUT + C OUT 124k R * ADJ 226k R1* INTERNALLY 100k CONNECTED FOR R0* FIXED OUTPUT VOLTAGE PARTS 50k ADJ/COMP REG *LTC1261CS14 ONLY LTC1261 • F02 and 8mA with the drain can be pulled above V CC without 7 ...

  • 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 of the LTC1261 can be affected by the capacitors it is connected to. The LTC1261 requires by- pass capacitors to ground for both the V The input capacitor provides most of LTC1261’s supply current while it is charging the flying capacitors ...

  • Page 10

    ... The LTC1261 uses a positive OUT , not a negative reference OUT 6 (4*) GND R1 LTC1261 10 (5*) ADJ –1.24V OUT OUT R2 *LTC1261CS8 LTC1261 • F06 Figure 6. External Resistor Connections ...

  • 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. 20mA through 312 gives 6.24V across the resistor, giving a net 5V 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 ...