Step-Down Controllers with
Synchronous Rectifier for CPU Power
Table 1. Component Selection for Standard 3.3V Applications
LOAD CURRENT
3A
4.75V to 28V
Notebook
300kHz
COMPONENT
1A
4.75V to 18V
PDA
2A
4.75V to 18V
Sub-Notebook
300kHz
4A
4.75V to 24V
High-End Notebook
300kHz
10A
4.5V to 6V
Input Range
Application
Frequency
Desktop 5V-to-3V
300kHz
150kHz
Motorola 1/2
MMDF3N03HD or 1/2 MMSF5N03HD or
Si9936
Motorola
Motorola
MTD20N03HDL
DPAK
Motorola
Q1 High-Side
MOSFET
International Rectifier
1/2 IRF7101
MTD75N03HDL
2
Si9410
D PAK
Motorola 1/2
MMDF3N03HD or 1/2 MMSF5N03HD or
Si9936
Motorola
Motorola
MTD20N03HDL
DPAK
Motorola
Q2 Low-Side
MOSFET
International Rectifier
1/2 IRF7101
MTD75N03HDL
2
Si9410
D PAK
2 x 220µF, 10V
Sanyo OS-CON
10SA220M
C1 Input
Capacitor
22µF, 35V AVX TPS 2 x 22µF, 35V AVX
or Sprague 595D
2 x 22µF, 35V AVX
TPS or Sprague 595D TPS or Sprague 595D TPS or Sprague 595D
4 x 22µF, 35V AVX
4 x 220µF, 10V
Sanyo OS-CON
10SA220M
C2 Output
Capacitor
150µF, 10V AVX TPS 150µF, 10V AVX TPS
220µF, 10V AVX TPS 3 x 220µF, 10V AVX
or Sprague 595D
or Sprague 595D
or Sprague 595D
TPS or Sprague 595D
1N5817 NIEC
EC10QS02L or
1N5819 NIEC
EC10QS03 or
1N5821 NIEC
NSQ03A04 or
1N5820 NIEC
NSQ03A02, or
1N5817 Motorola
MBR0502L SOD-89
D1 Rectifier
R1 Resistor
L1 Inductor
Motorola MBRS130T3 Motorola MBRS130T3 Motorola MBRS340T3 Motorola MBRS340T3
3 x 0.02Ω IRC
LR2010-01-R020
(3 in parallel)
0.062Ω IRC
LR2010-01-R062
0.039Ω IRC
LR2010-01-R039
0.025Ω IRC
LR2010-01-R025
0.015Ω IRC
LR2010-01-015
47µH, 1.2A Ferrite or
Kool-Mu
Sumida CD75-470
1.5µH, 11A, 3.5mΩ
Coiltronics
CTX03-12357-1
33µH, 2.2A Ferrite
Dale LPE6562-330MB Sumida CDRH125
10µH, 3A Ferrite
4.7µH, 5.5A Ferrite
Coilcraft DO3316-472
Table 2. Component Suppliers
FACTORY FAX
[Country Code]
FACTORY FAX
MANUFACTURER
USA PHONE
MANUFACTURER
USA PHONE
[Country Code]
AVX
(803) 946-0690 [1] 803-626-3123
(516) 435-1110 [1] 516-435-1824
(847) 639-6400 [1] 847-639-1469
(561) 241-7876 [1] 561-241-9339
(605) 668-4131 [1] 605-665-1627
(310) 322-3331 [1] 310-322-3332
(512) 992-7900 [1] 512-992-3377
(864) 963-6300 [1] 864-963-6521
(714) 969-2491 [1] 714-960-6492
(602) 303-5454 [1] 602-994-6430
(814) 237-1431
(800) 831-9172
Murata-Erie
[1] 814-238-0490
Central Semiconductor
Coilcraft
Coiltronics
Dale
International Rectifier
IRC
Kemet
NIEC
Sanyo
(805) 867-2555* [81] 3-3494-7414
(619) 661-6835 [81] 7-2070-1174
(408) 988-8000
[1] 408-970-3950
(800) 554-5565
Siliconix
Sprague
Sumida
TDK
(603) 224-1961 [1] 603-224-1430
(847) 956-0666 [81] 3-3607-5144
(847) 390-4461 {1} 847-390-4405
Matsuo
Motorola
Transpower Technologies (702) 831-0140 [1] 702-831-3521
* Distributor
losses due to MOSFET gate charge. The step-down
power-switching circuit consists of two N-channel
MOSFETs, a rectifier, and an LC output filter. The out-
put voltage is the average of the AC voltage at the
switching node, which is adjusted and regulated by
changing the duty cycle of the MOSFET switches. The
gate-drive signal to the N-channel high-side MOSFET
must exceed the battery voltage and is provided by a
flying capacitor boost circuit that uses a 100nF capaci-
tor connected to BST.
The MAX796 contains nine major circuit blocks, which
are shown in Figure 2.
______________________________________________________________________________________ 11
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
