IC LDO REG SMART DUAL 3.3V 8SOIC

LT1579CS8-3.3

Manufacturer Part NumberLT1579CS8-3.3
DescriptionIC LDO REG SMART DUAL 3.3V 8SOIC
ManufacturerLinear Technology
LT1579CS8-3.3 datasheet
 

Specifications of LT1579CS8-3.3

FunctionBack-Up ManagementBattery TypeSmart Batteries
Operating Temperature0°C ~ 125°CMounting TypeSurface Mount
Package / Case8-SOIC (0.154", 3.90mm Width)Lead Free Status / RoHS StatusContains lead / RoHS non-compliant
1
Page 1
2
Page 2
3
Page 3
4
Page 4
5
Page 5
6
Page 6
7
Page 7
8
Page 8
9
Page 9
10
Page 10
11
12
13
14
15
16
17
18
19
20
Page 1/20

Download datasheet (295Kb)Embed
Next
FEATURES
Maintains Output Regulation with Dual Inputs
Dropout Voltage: 0.4V
Output Current: 300mA
50 A Quiescent Current
No Protection Diodes Needed
Two Low-Battery Comparators
Status Flags Aid Power Management
Adjustable Output from 1.5V to 20V
Fixed Output Voltages: 3V, 3.3V and 5V
7 A Quiescent Current in Shutdown
Reverse-Battery Protection
Reverse Current Protection
Remove, Recharge and Replace Batteries Without
Daisy-Chained Control Outputs
Loss of Regulation
U
APPLICATIONS
Dual Battery Systems
Battery Backup Systems
Automatic Power Management for
Battery-Operated Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
U
TYPICAL
APPLICATION
5V Dual Battery Supply
IN1
OUT
+
2.7M
1 F
LBI1
1M
LT1579-5
SHDN
IN2
+
LBO1
2.7M
1 F
LB02
LBI2
BACKUP
1M
DROPOUT
BIASCOMP
GND
300mA Dual Input Smart
Battery Backup Regulator
DESCRIPTION
®
The LT
1579 is a dual input, single output, low dropout
regulator. This device is designed to provide an
uninterruptible output voltage from two independent input
voltage sources on a priority basis. All of the circuitry
needed to switch smoothly and automatically between
inputs is incorporated.
The LT1579 can supply 300mA of output current from
either input at a dropout voltage of 0.4V. Quiescent current
is 50 A, dropping to 7 A in shutdown. Two comparators
are included to monitor input voltage status. Two addi-
tional status flags indicate which input is supplying power
and provide an early warning against loss of output
regulation when both inputs are low. A secondary select
pin is provided so that the user can force the device to
switch from the primary input to the secondary input.
Internal protection circuitry includes reverse-battery pro-
tection, current limiting, thermal limiting and reverse-
current protection.
The device is available in fixed output voltages of 3V, 3.3V
and 5V, and as an adjustable device with a 1.5V reference
voltage. The LT1579 regulators are available in narrow
16-lead SO and 16-lead SSOP packages with all features,
and in SO-8 with limited features.
5V
300mA
+
4.7 F
SS
TO
POWER
MANAGEMENT
0.01 F
1579 TA01
LT1579
U
Automatic Input Switching
12
V
= 10V
IN2
10
V
SWITCHOVER
IN1
I
= 50mA
LOAD
POINT
8
80
I
I
6
60
IN1
IN2
4
40
2
20
0
0
5.05
5.00
4.95
0
2
4
6
8
10
12
14
16
18
20
TIME (ms)
1578 TA02
1

LT1579CS8-3.3 Summary of contents

  • Page 1

    ... Reverse Current Protection Remove, Recharge and Replace Batteries Without Daisy-Chained Control Outputs Loss of Regulation U APPLICATIONS Dual Battery Systems Battery Backup Systems Automatic Power Management for Battery-Operated Systems , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATION 5V Dual Battery Supply IN1 OUT + 2. ...

  • Page 2

    ... SEE APPLICATION INFORMATION SECTION 15793 T = 125 C, JMAX 157933 T = 125 C, JMAX 15795 ORDER PART NUMBER LT1579CS8-3 V POWER IN1 INPUTS V LT1579CS8-3.3 IN2 CONTROL SHDN LT1579CS8-5 INPUT GND S8 PART MARKING 15793 SEE APPLICATION INFORMATION SECTION 157933 T JMAX 15795 ORDER PART NUMBER TOP VIEW 16 GND ...

  • Page 3

    ELECTRICAL CHARACTERISTICS PARAMETER CONDITIONS Regulated Output LT1579 IN1 Voltage (Note 1) 4V < V IN1 LT1579-3 IN1 4.3V < V LT1579 IN1 6V < V IN1 Adjust Pin Voltage LT1579 V ...

  • Page 4

    LT1579 ELECTRICAL CHARACTERISTICS PARAMETER CONDITIONS Adjust Pin Bias Current (Notes 2, 7) Minimum Input Voltage I = 0mA LOAD (Note 8) Minimum Load Current LT1579 V IN1 Secondary Select Switch from V IN2 Threshold Switch ...

  • Page 5

    W U TYPICAL PERFORMANCE CHARACTERISTICS Guaranteed Dropout Voltage 0.8 = TEST POINTS 0.7 T 125 C J 0.6 0 0.4 0.3 0.2 0 100 150 200 250 300 OUTPUT CURRENT (mA) 1579 ...

  • Page 6

    LT1579 W U TYPICAL PERFORMANCE CHARACTERISTICS Input and Ground Pin Current 1 IN2 IN1 1.0 0.8 0.6 I GND 0.4 0.2 0 –0.2 –0.1 0 0.1 0.2 0.3 0.4 V – V (V) IN1 OUT Input and Ground ...

  • Page 7

    W U TYPICAL PERFORMANCE CHARACTERISTICS Ground Pin Current IN1 IN2 OUT(NOMINAL 100 150 200 250 300 OUTPUT CURRENT (mA) 1579 G37 Shutdown ...

  • Page 8

    LT1579 W U TYPICAL PERFORMANCE CHARACTERISTICS Logic Flag Input Current (Output High LOGIC FLAG VOLTAGE (V) 1579 G22 Low-Battery Comparator Hysteresis ...

  • Page 9

    W U TYPICAL PERFORMANCE CHARACTERISTICS Ripple Rejection 100 I = 150mA LOAD 50mV RIPPLE RMS OUT SOLID 60 TANTALUM 4.7 F OUT SOLID ...

  • Page 10

    LT1579 PIN FUNCTIONS out of the pin (see curve of Adjust Pin Bias Current vs Temperature in the Typical Performance Characteristics load needed on the output of the adjustable part to ...

  • Page 11

    PIN FUNCTIONS LBO1: This is the open collector output of the low-battery comparator LB1. This output pulls low when the com- parator input drops below the threshold voltage. The LBO1 output voltage is 1V when sinking 5mA, ...

  • Page 12

    LT1579 U U APPLICATIONS INFORMATION Device Overview The LT1579 is a dual input, single output, low dropout linear regulator. The device is designed to provide an uninterruptible output voltage from two independent input voltage sources on a priority basis. All ...

  • Page 13

    U U APPLICATIONS INFORMATION A small capacitor placed in parallel with the top resistor (R2) of the output divider is necessary for stability and transient performance of the adjustable LT1579. The impedance 10kHz should be less than ...

  • Page 14

    LT1579 U U APPLICATIONS INFORMATION if V > typically only 3 A. The primary input will IN2 IN1 automatically go into standby mode as the primary input drops below the output voltage. The primary input can also be ...

  • Page 15

    U U APPLICATIONS INFORMATION Example: The low-battery detector must be tripped at a terminal voltage of 5.5V. There is a 100k pull-up resistor the output of the comparator and 200mV of hysteresis is needed to prevent chatter. ...

  • Page 16

    LT1579 U U APPLICATIONS INFORMATION Five milestones are noted on the timing diagram. Time A is where the primary input voltage drops enough to trip the low-battery detector LB1. The trip threshold for LB1 is set at set at 5.5V, ...

  • Page 17

    U U APPLICATIONS INFORMATION resistance from the junction to a ground lead is 40 C/W for 16-lead SSOP, 32 C/W for 16-lead SO and 35 C/W for 8-lead S0. Table 2. 8-Lead SO Package (S8) COPPER AREA TOPSIDE* BACKSIDE BOARD ...

  • Page 18

    LT1579 U U APPLICATIONS INFORMATION The inputs of the device can withstand reverse voltages up to 20V. Current flow into the device will be limited to less than 1mA (typically less than 100 A) and no negative voltage will appear ...

  • Page 19

    ... 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 20

    ... Switch Driver LTC1479 PowerPath Controller for Dual Battery Systems LT1521 300mA Low Dropout Micropower Regulator with Shutdown Hot Swap and PowerPath are trademarks of Linear Technology Corporation. Linear Technology Corporation 20 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 TELEX: 499-3977 www.linear-tech.com ...