Pin Description

Pin No.

Pin Name

I/O

Description

1, 3, 7

NC

¾

No connection

2

LX

I

Switching pin

4

VSS

¾

Negative power supply, ground

5

CP

I

External capacitor for adjusting VDET output delay time.

6

VDET

O

Voltage detector open drain output (needs a pull-high resistor)

8

VOUT

O

DC/DC converter voltage output

Absolute Maximum Ratings

Storage Temperature ..........................

-40°Cto125°C

Operating Temperature .........................

-25°Cto70°C

Power Consumption ........................................ 150mW

Note: These are stress ratings only. Stresses exceeding the range specified under

²Absolute Maximum Ratings² may

cause substantial damage to the device. Functional operation of this device at other conditions beyond those

listed in the specification is not implied and prolonged exposure to extreme conditions may affect device reliabil-

ity.

Electrical Characteristics

Ta=25

Symbol

Parameter

Test Conditions

Min.

Typ.

Max.

Unit

Output Voltage

¾

2.56

2.7

2.75

V

Input Voltage

¾¾

¾

5V

Vstart

Starting Voltage

L=330

¾

0.95

1.1

V

Vhold

Voltage Hold

¾

0.9

¾¾

V

Iin

Current Consumption

Measure at no load

¾

14

20

mA

LX Switching Current

60

¾¾

mA

LX Leakage Current

¾¾

¾

1

mA

Oscillator Frequency

¾

139

¾

kHz

H

®L Detectable Voltage

¾

2.0

2.1

2.2

V

L

®H Detectable Voltage

¾

2.2

2.3

2.4

V

Hysteresis Width

¾¾

0.2

¾

V

0.5

¾¾

mA

HT7627

Rev. 1.00

2

January 18, 2002

Functional Description

Operation of step-up DC/DC converter

The following figures show the basic circuit configura-

tion of the step-up operation of the IC. In the configura-

tion, when the transistor tr is entirely Off, the output

voltage reduced by inductor L and Schottky diode SD.

When tr has been On for time ton and is suddenly turned

the energy accumulated during the ton period. There-

fore, the peak value of the voltage generated at that time