Rainbow-electronics MAX1712 Bedienungsanleitung PDF herunterladen (Seite 10)

MAX1710/MAX1711/MAX1712

rent-mode PWMs while also avoiding the problems

caused by widely varying switching frequencies in con-

ventional constant-on-time and constant-off-time PWM

schemes.

+5V Bias Supply (V

and V

)

The MAX1710/MAX1711/MAX1712 require an external

+5V bias supply in addition to the battery. Typically, this

+5V bias supply is the notebook’s 95% efficient 5V sys-

tem supply. Keeping the bias supply external to the IC

improves efficiency and eliminates the cost associated

with the +5V linear regulator that would otherwise be

needed to supply the PWM circuit and gate drivers. If

stand-alone capability is needed, the +5V supply can be

generated with an external linear regulator such as the

MAX1615.

The battery and +5V bias inputs can be tied together if

the input source is a fixed 4.5V to 5.5V supply. If the +5V

bias supply is powered up prior to the battery supply, the

enable signal (SHDN) must be delayed until the battery

voltage is present in order to ensure startup. The +5V

bias supply must provide V

and gate-drive power, so

the maximum current drawn is:

High-Speed, Digitally Adjusted

Step-Down Controllers for Notebook CPUs

10 ______________________________________________________________________________________

BATT

4.5V TO 28V

+5V

BIAS SUPPLY

3 x 470µF

KEMET T510

PANASONIC

ETQP6F2R0HFA

POWER-GOOD

INDICATOR

*MAX1710 ONLY

**MAX1711/MAX1712 ONLY

2µH

OUT

1.25V TO 2V AT 7A (MAX1710)

0.925V TO 2V AT 7A (MAX1711)

1.1V TO 1.85V AT 7A (MAX1712)

SHDN

V+

221

CMPSH-3

1µF

0.1µF

1µF

470pF

TO V

100k

(OPTIONAL OVP

REVERSE-POLARITY

CLAMP)

1µF

20Ω

C1 3 x 10µF/30V

SKIP

DAC

INPUTS

ON/OFF

CONTROL

LOW-NOISE

CONTROL

BST

PGND

FBS

GNDS

Q1 = IRF7807

Q2 = IRF7805

D1, D3 = MBRS130T3 (OPTIONAL)

C1 = SANYO OS-CON (30SC10M)

PGOOD

MAX1710

MAX1711

MAX1712

+5V

D4**

TON

REF

GND

(OPTIONAL)

ILIM OVP*

Figure 1. Standard Application Circuit

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 ... 27 28

MAX1710/MAX1711/MAX1712 1
MAX1710/MAX1711 14

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