1

LT1611

Inverting 1.4MHz Switching

Regulator in SOT-23

s

s

– 5V at 150mA from a 5V Input

s

Better Regulation Than a Charge Pump

s

Effective Output Impedance: 0.14

Ω

s

Uses Tiny Capacitors and Inductors

s

Internally Compensated

s

Fixed Frequency 1.4MHz Operation

s

Low Shutdown Current: <1

µA

s

s

Tiny 5-Lead SOT-23 Package

The LT

current mode DC/DC converter. Intended for use in small,

low power applications, it operates from an input voltage

as low as 1.1V and switches at 1.4MHz, allowing the use

of tiny, low cost capacitors and inductors 2mm or less in

height. Its small size and high switching frequency enable

the complete DC/DC converter function to consume less

than 0.25 square inches of PC board area. Capable of

generating – 5V at 150mA from a 5V supply or – 5V at

100mA from a 3V supply, the LT1611 replaces nonregulated

“charge pump” solutions in many applications.

The LT1611 operates in a dual inductor inverting topology

which filters the input side as well as the output side of the

DC/DC converter. Fixed frequency switching ensures a

clean output free from low frequency noise typically present

with charge pump solutions. No load quiescent current of

the LT1611 is 3mA, while in shutdown quiescent current

drops to 0.5

differential of up to 33V.

The LT1611 is available in the 5-lead SOT-23 package.

s

MR Head Bias

s

Digital Camera CCD Bias

s

LCD Bias

s

GaAs FET Bias

s

Positive-to-Negative Conversion

5V

–5V

150mA

1611 TA01

SW

L1A

22

µH

L1B

22

µH

D1

GND

LT1611

C1: AVX TAJB226M010

C2: TAIYO YUDEN LMK212BJ105MG

C3: TAIYO YUDEN JMK325BJ226MM (1210 SIZE)

D1: MBR0520

L1: SUMIDA CLS62-220 OR 2

× MURATA LQH3C220 (UNCOUPLED)

C1

22

µF

C3

22

µF

C2

1

µF

R2

10k

R1

29.4k

1200pF

NFB

SHDN

+

Figure 1. 5V to – 5V, 150mA Low Noise Inverting DC/DC Converter

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

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

20mV/DIV

AC COUPLED

LOAD CURRENT

150mA

50mA

100

µs/DIV

1611 F10

Transient Response