IC SW CAP/INV -4.5V 15MA 8SOIC

LTC1261CS8-4.5

Manufacturer Part NumberLTC1261CS8-4.5
DescriptionIC SW CAP/INV -4.5V 15MA 8SOIC
ManufacturerLinear Technology
TypeSwitched Capacitor (Charge Pump), Inverting
LTC1261CS8-4.5 datasheet
 

Specifications of LTC1261CS8-4.5

Internal Switch(s)YesSynchronous RectifierNo
Number Of Outputs1Voltage - Output-4.5V
Current - Output15mAFrequency - Switching550kHz
Voltage - Input3 ~ 8 VOperating Temperature0°C ~ 70°C
Mounting TypeSurface MountPackage / Case8-SOIC (3.9mm Width)
Output Voltage-1.25 to -8VOutput Current15mA
Operating Supply Voltage (min)3VOperating Supply Voltage (max)8V
Operating Temp Range0C to 70COperating Temperature ClassificationCommercial
Package TypeSOIC NPin Count8
MountingSurface MountLead Free Status / RoHS StatusContains lead / RoHS non-compliant
Power - 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

LTC1261CS8-4.5 Summary of contents

  • Page 1

    ... 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. It requires a single external 0.1 F capacitor and provides adjustable and fixed output voltage options in 8-pin SO packages ...

  • Page 2

    ... REG CC = 1.24V ADJ = V SHDN CC = 15mA U W ORDER PART TOP VIEW NUMBER 1 8 SHDN LTC1261CS8 2 7 REG LTC1261CS8 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 ...

  • Page 3

    ... F unless otherwise specified – (Note 7) MIN TYP MAX MIN TYP MAX – (Note 7) MIN TYP MAX MIN TYP MAX – + and C2 floating. For the LTC1261CS8 in doubler mode, + – there are no C2 pins. – 12V. CC UNITS % UNITS UNITS UNITS ...

  • 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 LTC1261CS in doubler mode, connect a 0.1 F capacitor from C1 – – C1 (Pin 3/Pin 3): C1 Negative Input. Connect a 0 – ...

  • Page 6

    ... S capacitor to invert the input supply voltage, and the output voltage is stored on the output bypass capacitor between switch cycles. The LTC1261CS8 is always configured in doubler mode and has only one pair of flying capacitor pins (Figure 1a). The LTC1261CS can be configured in doubler mode by connecting a single flying capacitor + – ...

  • 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 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 ...