DS1227 Datasheet, PDF(3/20 Page) Dallas Semiconductor

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DS1227 Datasheet, PDF (3/20 Pages) Dallas Semiconductor – KickStarter Chip

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DS1227

INPUT SUPPLY VOLTAGE

The Kickstarter is capable of operating either in a regu-

lated step-up DC-to-DC conversion (boost) mode or in a

non-regulated supply voltage Pass-Through mode.

In boost mode, the Kickstarter is designed to provide a

regulated +5V output on the VCCO1, VCCO2, or VCCO3

voltage supply output pins from a +3V lithium source.

Figure 1 illustrates the standard configuration for use of

this mode. The BOOST pin should be tied low in order to

enable step-up DC-to-DC conversion. VDCI is used for

the DC power supply input and is tied through an induc-

tor (270 ÂµH typical) to a +3V lithium cell. VDCO is the

main DC output which is switched to the VCCO1, VCCO2,

and VCCO3 outputs. This pin requires a large capacitor

(typically 100 ÂµF) to ground for the boost regulation low

pass output network. Further details of the boost voltage

regulator operation are given in the âBoost Mode Opera-

tionâ section of this data sheet.

Figure 2 and Figure 3 illustrate the required configura-

tions to select the supply voltage Pass-Through mode of

operation. In both of these configurations the BOOST

pin should be strapped directly to the VDCO pin. This

connection causes the BOOST pin to remain at a high

level at all times that a battery is connected. As a result,

the internal boost regulator will be disabled when kick-

starting occurs. When a +5V supply is used as the input

DC power source, it should be directly connected to the

VDCO in parallel with a filter capacitor as shown in Figure

2. The VDCI input itself should be grounded in this con-

figuration.

If a +6V supply is used, then it should be connected to

the VDCI pin. A filter capacitor should still be connected

to VDCO. The voltage on VDCO and subsequently on

VCCO1, VCCO2, and VCCO3 (when they are enabled fol-

lowing kickstarting) will be a diode drop below the VDCI

voltage.

In both the Boost and Pass-Through modes, the

DS1227 uses the voltage on VDCO as its own internal

supply.

DS1227 BOOST MODE CONFIGURATION Figure 1

270 uH (typ.)

+3V

DS1227

KICKSTARTER

VDCI

VCC01

VCC02

VCC03

.01 uF

Bypass

(typ.)

100 uF

Filter

(typ.)

VDCO

BOOST

GND

022698 3/20

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