5

LTC1550/LTC1551

Spot Noise

FREQUENCY (kHz)

1

0.01

1

0.1

10

10

100

LTC1550/51 • G12

Output Spectrum

FREQUENCY (Hz)

100k

90

80

70

60

50

40

30

20

10

0

–10

1M

10M

LT1550/51 • G13

Spot Noise

FREQUENCY (kHz)

1

0.01

1

0.1

10

10

100

LTC1550/51 • G14

SHDN: Shutdown (TTL Compatible). This pin is active low

(SHDN) for the LTC1550 and active high (SHDN) for the

LTC1550 operates normally. When SHDN is pulled low

(high for LTC1551), the LTC1550 enters shutdown mode.

In shutdown, the charge pump stops, the output collapses

to 0V, and the quiescent current drops typically to 0.2

µA.

4.5V and 6.5V for the fixed voltage LTC1550CS8-4.1/

LTC1551CS8-4.1. The adjustable voltage LTC1550CGN/

LTC1550IGN operates with a VCC range of 2.7V to 6.5V.

Output voltage and output load current conditions depend

on the VCC supply voltage. Consult the Electrical Charac-

teristics table and Typical Performance Characteristics for

guaranteed test points. The difference between the input

voltage and output should never be set to exceed 14V or

PGND (GND for 8-pin packages) with at least a 0.1

µF

capacitor placed in close proximity to the chip. A 4.7

µF or

larger bypass capacitor is recommended to minimize

noise and ripple at the output.

µFcapacitorbetween

to ground with a 4.7

µF or larger capacitor to ensure

regulator loop stability. At least 10

µF is recommended to

provide specified output ripple. An additional 0.1

µF low

ESR capacitor is recommended to minimize high fre-

quency spikes at the output.

µF capacitor from

GND: Ground. Connect to a low impedance ground. A

ground plane will help minimize regulation errors.

0.1

µF storage capacitor to ground.

regulator uses this pin to sense the output voltage. For

optimum regulation, SENSE should be connected close to

the output load.

SSOP PACKAGE ONLY

PGND: Power Ground. Connect to a low impedance ground.

PGND should be connected to the same potential as

AGND.

AGND: Analog Ground. Connect to a low impedance

ground. AGND should be connected to a ground plane to

minimize regulation errors.