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ST619

DC-DC CONVERTER REGULATED 5V CHARGE PUMP

STMicroelectronics 

ST619LB SERIES

OPERATING PRINCIPLE

The ST619LB is able to provide a regulated 5V

output from a 2V to 3.6V (two battery cells) input.

Internal charge pump and external capacitors

generate the 5V output, eliminating the need for

inductors. The output voltage is regulated to 5V,

±4% by a pulse skipping controller that turns on

the charge pump when the output voltage begins

to drop. To maintain the greatest efficiency the

internal charge pump of the device operates as a

voltage doubler when VI ranges from 3.0V to 3.6V

and as a voltage tripler when VI ranges from 2.0V

to 2.5V.

When VI ranges from 2.5V to 3.0V , the ST619LB

switches between doubler and tripler mode on

alternating cycles, making a 2.5 x VI charge pump.

To further enhance the efficiency over the input

range, an internal comparator selects the higher of

VI or VO to run the ST619LB’s circuitry. With VI =

2V and IO = 20mA the typical efficiency value is

80%.

In tripler mode (see block diagram), when the S1

switches close, the S2 switches open and

capacitors C1 and C2 charge up to VI. On the

second half of the cycle, C1 and C2 are connected

in series between IN and OUT when the S1

switches open and S2 switches close. In the

doubler mode only C2 is used. During one

oscillator cycle, energy is transferred from the

input to the charge pump capacitors, and then

from the charge pump capacitors to the output

capacitors and load. The number of cycles within

a given time frame increases as the load

increases or as the input supply voltage

decreases. In the limiting case , the charge pumps

operate continuously, and the oscillator frequency

is nominally 500kHz.

Shut Down Mode

The ST619LB enters low power shut down mode

when SHDN is a logic high. In shut down mode,

OUT is disconnected from the IN and VO falls to

0V. The SHDN pin is connected to ground for

normal operation. SHDN is a CMOS compatible

input.

ABSOLUTE MAXIMUM RATINGS

Symbol

Parameter²

Value

Unit

VI

DC Input Voltage

-0.3 to 5.5

V

VO

Output Voltage

-0.3 to 5.5

V

VSHDN Shutdown Input Voltage

-0.3 to (VI + 0.3)

V

IO

Output Current Continuous

120

mA

Tstg Storage Temperature Range

-55 to +150

°C

Top

Operating Junction Temperature Range

-40 to +85

°C

Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these condition is

not implied.

THERMAL DATA

Symbol

Parameter

Rthj-amb Thermal Resistance Junction-ambient (*)

(*) This value depends from thermal design of PCB on which the device is mounted.

SO-8

160

DIP-8

100

Unit

°C/W

2/9

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