SM8172A

SEIKO NPC CORPORATION —5

11-3. DC/DC Converter

VIN1 = VIN2 = 5.0V, GND = PGND = 0V, Ta = 25

°C unless otherwise noted.

Parameter

Pin

Symbol

Condition

Rating

Unit

min

typ

max

Current consumption 1

VIN1, 2

No load, switching stopped

–

0.35

0.75

mA

Current consumption 2

VIN1, 2

FB = VIN1, LX = Open

–

2.5

5.5

mA

*1. The soft start time is the interval during which the output current is limited internally in the IC, and is different from the DC/DC converter output raise

time. If the maximum load current is output after soft start time startup, the output voltage does not fall. But, if the maximum load current is output

before soft start time startup, it should be careful that the output voltage may fall.

The LX starts the switching operation after 42

µs from ENDCO rising. After switching operation startup, the output current limit operates like linear

increase (load current = 0A). The DC/DC converter output voltage rise time varies with the load current, output capacitance, and other conditions.

0.2

0.6

1.0

ms

0.8

–

1.8

V

FB voltage

FB

0.588

0.6

0.612

V

900

–

–

mA

Switching frequency

LX

1.7

2.0

2.3

MHz

Supply-side switch ON resistance

LX

–

0.3

–

Ω

GND-side switch ON resistance

LX

–

0.3

–

Ω

LX leakage current

LX

Standby mode, LX = 1/2VIN

–1.0

–

1.0

µA

Overcurrent protection circuit

operating current

LX

Supply-side switch

–

1.5

–

A

ENDCO

Current limit

42

µsec (typ)

High

Low

DCOUT

28

µsec (typ)

1.5A (typ)

1.8V

1.0V

Soft start time

LX switching start