Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - DC/DC voltage regulator Switched-capacitor voltage converter SOIC 8

LTC1514-3.3/LTC1514-5

Step-Up/Step-Down Switched

Capacitor DC/DC Converters

with Low-Battery Comparator

■

3.3V or 5V Output Voltages

■

2V to 10V Input Voltage Range

■

Up to 50mA Output Current

■

Only Three External Capacitors Required

■

Soft Start Limits Inrush Current at Turn-On

■

Low Operating Current: 60µA

■

Low Shutdown Current: 10µA

■

Shutdown Disconnects Load from V

■

Short-Circuit and Overtemperature Protected

■

650kHz Switching Frequency

■

Low-Battery Comparator Active in Shutdown

■

Available in SO-8 Package

FEATURES

DESCRIPTION

The LTC

1514-3.3/LTC1514-5 are micropower switched

capacitor DC/DC converters that produce a regulated

output voltage by either stepping up or stepping down

the input voltage. Output voltage is fixed at either 3.3V

(LTC1514-3.3) or 5V (LTC1514-5) by an internal resistor

divider.

A unique architecture allows the parts to accommodate

a wide input voltage range (2V to 10V) while maintaining

±4% regulation. Additional circuitry prevents excessive

inrush current and output voltage ripple when large V

to V

OUT

differentials are present.

An internal uncommitted comparator is kept active in

shutdown. The comparator has an open-drain output for

flexible interfacing.

The parts are short-circuit and overtemperature pro-

tected. Battery life is maximized by very low operating

currents (I

= 60µA typ, 10µA in shutdown). Both parts

are available in an SO-8 package.

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

APPLICATIONS

■

Battery-Operated Equipment

■

Smart Card Readers

■

Local Power Supplies

■

Handheld Instruments

■

Battery Backup Supplies

INPUT VOLTAGE (V)

OUTPUT VOLTAGE (V)

LT1514 • TA02

5.2

5.1

5.0

4.9

4.8

OUT

= 10mA

TYPICAL APPLICATION

1

2

3

8

7

6

SHDN

LBO

LBI

GND

OUT



–

LTC1514-5

100k

OUT

= 5V

OUT

= 50mA

0.22µF

10µF



4-CELL

NiCd

1.33M

499k

ON OFF

LOW BAT

1514 TA01

5V Step-Up/Step-Down Power Supply with Low-Battery Detect

LTC1514-5 Output Voltage

vs Input Voltage

Summary of content (8 pages)

PAGE 1
LTC1514-3.3/LTC1514-5 Step-Up/Step-Down Switched Capacitor DC/DC Converters with Low-Battery Comparator U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ The LTC®1514-3.3/LTC1514-5 are micropower switched capacitor DC/DC converters that produce a regulated output voltage by either stepping up or stepping down the input voltage. Output voltage is fixed at either 3.3V (LTC1514-3.3) or 5V (LTC1514-5) by an internal resistor divider. 3.
PAGE 2
LTC1514-3.3/LTC1514-5 W U U W W U W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) VIN to GND ................................................ – 0.3V to 12V VOUT to GND ............................................. – 0.3V to 12V SHDN, LBI, LBO to GND ........................... – 0.3V to 12V VOUT Short-Circuit Duration ............................. Indefinite Operating Temperature Range Commercial ............................................. 0°C to 70°C Industrial ...................
PAGE 3
LTC1514-3.3/LTC1514-5 U W TYPICAL PERFORMANCE CHARACTERISTICS LTC1514-3.3 Efficiency vs Output Current LTC1514-5 Efficiency vs Output Current 100 100 VIN = 2.7V VIN = 2V 80 250 80 EFFICIENCY (%) VIN = 4.4V VIN = 2.7V 60 VIN = 6V OUTPUT VOLTAGE RIPPLE (mVP-P) VOUT = 3.3V TA = 25°C EFFICIENCY (%) LTC1514-3.3 Output Voltage Ripple vs Input Voltage VIN = 6V 40 20 VIN = 3.3V 60 VIN = 8V 40 20 VOUT = 5V TA = 25°C 0 0.01 0.1 1 10 OUTPUT CURRENT (mA) 0 0.
PAGE 4
LTC1514-3.3/LTC1514-5 U W TYPICAL PERFORMANCE CHARACTERISTICS LTC1514-5 Step-Down Mode Load Transient Response LTC1514-5 Step-Up Mode Load Transient Response VOUT AC COUPLED 100mV/DIV VOUT AC COUPLED 100mV/DIV 50mA IOUT 50mA/DIV IOUT 50mA/DIV 0mA VIN = 8V, VOUT = 5V, COUT = 10µF, TA = 25°C VIN = 3.3V, VOUT = 5V, COUT = 10µF, TA = 25°C 1514 G10 1514 G11 W BLOCK DIAGRAM C1 – VIN C1 + STEP-UP/STEP-DOWN CHARGE PUMP VOUT SHDN – 650kHz OSCILLATOR + LBO – LBI + 1.
PAGE 5
LTC1514-3.3/LTC1514-5 U U U PIN FUNCTIONS battery comparator and 1.145V reference are kept alive in shutdown. GND (Pin 4): Ground. Should be tied to a ground plane for best performance. C1 – (Pin 5): Charge Pump Flying Capacitor, Negative Terminal. C1 + (Pin 6): Charge Pump Flying Capacitor, Positive Terminal. VIN (Pin 7): Charge Pump Input Voltage. May be between 2V and 8V (LTC1514-3.3) or between 2.7V and 10V (LTC1514-5).
PAGE 6
LTC1514-3.3/LTC1514-5 U U W U APPLICATIONS INFORMATION output pin cause high frequency voltage spikes on VOUT with every clock cycle. There are several ways to reduce the output voltage ripple. A larger COUT capacitor (22µF or greater) will reduce both the low and high frequency ripple due to the lower COUT charging and discharging dV/dt and the lower ESR typically found with higher value (larger case size) capacitors.
PAGE 7
LTC1514-3.3/LTC1514-5 U U W U APPLICATIONS INFORMATION resistor divider (see Figure 2). Since the low-battery comparator is kept alive in shutdown, it may be used to protect batteries against deep discharge by shutting down the power supply when the battery voltage gets too low. The open-drain comparator output allows for flexible interfacing between the LBO output and external logic. LBO pull-up resistors in the 50k to 1M range are recommended. U TYPICAL APPLICATIONS N 3.
PAGE 8
LTC1514-3.3/LTC1514-5 U TYPICAL APPLICATIONS N Low Power Dual Output Supply (Maximum Combined IOUT = 50mA) ON OFF 10Ω Q2 220k 1 Q1 VOUT 3.3V ±4% 47k + 750k 1% 2 VIN LBO 2.2nF LTC1514-5 3 LBI 10µF 402k 1% VOUT SHDN 4 C1+ C1 GND – 8 VOUT 5V ±4% VIN 2.7V TO 10V 7 6 + 0.