Rainbow Electronics MAX1715 User Manual

Page 11

MAX1715

Ultra-High Efficiency, Dual Step-Down

Controller for Notebook Computers

______________________________________________________________________________________

The power input and +5V bias inputs can be connected
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 (ON1, ON2) must
be delayed until the battery voltage is present to ensure
start-up. The +5V bias supply must provide V

and

gate-drive power, so the maximum current drawn is:

BIAS

= I

+ f (QG1 + QG2) = 5mA to 30mA (typ)

where ICC is 1mA typical, f is the switching frequency,
and QG1 and QG2 are the MOSFET data sheet total
gate-charge specification limits at V

= 5V.

Free-Running, Constant-On-Time PWM

Controller with Input Feed-Forward

The Quick-PWM control architecture is a pseudo-fixed-
frequency, constant-on-time current-mode type with
voltage feed-forward (Figure 3). This architecture relies
on the output filter capacitor’s ESR to act as the cur-
rent-sense resistor, so the output ripple voltage pro-
vides the PWM ramp signal. The control algorithm is
simple: the high-side switch on-time is determined sole-
ly by a one-shot whose period is inversely proportional
to input voltage and directly proportional to output volt-
age. Another one-shot sets a minimum off-time (400ns
typ). The on-time one-shot is triggered if the error com-
parator is low, the low-side switch current is below the

Table 1. Component Selection for Standard Applications

Table 2. Component Suppliers

4.75V to 5.5V

7V to 20V

Input Range

100µF, 10V
Sanyo POSCAP
10TPA100M

470µF, 4V Sanyo
POSCAP 4TPB470M

C2 Output Capacitor

100µF, 10V
Sanyo POSCAP
10TPA100M

10µF, 25V
Taiyo Yuden
TMK432BJ106KM

C1 Input Capacitor

3.3µH
TOKO D73LC

3.1µH
Sumida CDRH125

4.4µH
Sumida CDRH125

L1 Inductor

—

Nihon EP10QY03

D2 Rectifier

International Rectifier
1/2 IRF7301

Fairchild
Semiconductor
1/2 FDS6982A

Q2 Low-Side MOSFET

International Rectifier
1/2 IRF7301

Fairchild
Semiconductor
1/2 FDS6982A

Q1 High-Side MOSFET

600kHz

345kHz

255kHz

Frequency

3.3V at 1.5A

1.8V at 4A

2.5V at 4A

COMPONENT

[1] 602-994-6430

602-303-5454

Motorola

[1] 408-986-1442

408-986-0424

Kemet

[1] 408-721-1635

408-822-2181

Fairchild Semiconductor

[1] 561-241-9339

561-241-7876

Coiltronics

[1] 847-639-1469

847-639-6400

Coilcraft

[1] 516-435-1824

516-435-1110

Central Semiconductor

[1] 803-626-3123

803-946-0690

AVX

FACTORY FAX

[Country Code]

USA PHONE

MANUFACTURER

[1] 714-960-6492

714-969-2491

Matsuo

[1] 310-322-3332

310-322-3331

International Rectifier

[1] 408-573-4159

408-573-4150

Taiyo Yuden

[1] 603-224-1430

603-224-1961

Sprague

[1] 408-970-3950

408-988-8000
800-554-5565

Siliconix

[81] 7-2070-1174

619-661-6835

Sanyo

[81] 3-3494-7414

805-867-2555*

NIEC (Nihon)

[1] 814-238-0490

814-237-1431
800-831-9172

Murata

[81] 3-3607-5144

847-956-0666

Sumida

[1] 847-390-4405

847-390-4461

TDK

*Distributor

7V to 20V

(2) 470µF, 6V Kemet
T510X477108M0
06AS

(2) 10µF, 25V
Taiyo Yuden
TMK432BJ106KM

1.5µH Sumida
CEP125-1R5MC

Motorola
MBRS340T3

Fairchild
Semiconductor
FDS6670A

International
Rectifier IRF7811

255kHz

1.3V at 8A

7V to 20V

330µF, 6V AVX
TPSV337M006R
0060

10µF, 25V
Taiyo Yuden
TMK432BJ106KM

6.8µH
Coiltronics UP2B

Nihon EP10QY03

Fairchild
Semiconductor
1/2 FDS6990A

255kHz

5V at 3A

[1] 708-699-1194

800-PIK-TOKO

TOKO