MAX8741EAI+T Maxim Integrated, MAX8741EAI+T Datasheet - Page 12

• Manufacturer Part Number: MAX8741EAI+T
• Description: Current & Power Monitors & Regulators 500kHz Multi-Out Pwr Supply Controller
• Manufacturer: Maxim Integrated

Specifications of MAX8741EAI+T

• Rohs: yes
• Product: Power Monitors
• Supply Voltage - Max: 30 V
• Supply Voltage - Min: 4.2 V
• Input Voltage Range: 4.2 V to 30 V

500kHz Multi-Output Power-Supply Controllers
with High Impedance in Shutdown
The basic MAX8741 dual-output 3.3V/5V buck converter
(Figure 1) is easily adapted to meet a wide range of
applications with inputs up to 28V by substituting com-
ponents from Table 1. These circuits represent a good
set of tradeoffs between cost, size, and efficiency,
while staying within the worst-case specification limits
for stress-related parameters, such as capacitor ripple
current. Do not change the frequency of these circuits
without first recalculating component values (particularly
inductance value at maximum battery voltage). Adding
a Schottky rectifier across each synchronous rectifier
improves the efficiency of these circuits by approxi-
mately 1%, but this rectifier is otherwise not needed
because the MOSFETs required for these circuits typi-
cally incorporate a high-speed silicon diode from drain
to source. Use a Schottky rectifier rated at a DC current
equal to at least one-third of the load current.
Table 1. Component Selection for Standard 3.3V/5V Application
12
Input Range
Frequency
Q1, Q3 High-Side
MOSFETs
Q2, Q4 Low-Side
MOSFETs with Integrated
Schottky Diodes
C3 Input Capacitor
C1 Output Capacitor
C2 Output Capacitor
R1, R2 Resistors
L1 Inductor
L2 Inductor
______________________________________________________________________________________
COMPONENT
Standard Application Circuit
7V to 24V
333kHz
1/2 Fairchild FDS6982S or
1/2 International Rectifier
IRF7901D1
1/2 Fairchild FDS6982S or
1/2 International Rectifier
IRF7901D1
3 x 10µF, 25V ceramic
Taiyo Yuden TMK432BJ106KM
150µF, 6V POSCAP
Sanyo 6TPC150M
2 x 150µF, 4V POSCAP
Sanyo 4TPC150M
0.018Ω
Dale WSL2512-R018-F
10µH, 4.5A Ferrite
Sumida CDRH124-100
7.0µH, 5.2A Ferrite
Sumida CEI122-H-7R0
4A/333kHz
500kHz
7V to 24V
1/2 Fairchild FDS6982S or
1/2 International Rectifier
IRF7901D1
1/2 Fairchild FDS6982S or
1/2 International Rectifier
IRF7901D1
3 x 10µF, 25V ceramic
Taiyo Yuden TMK432BJ106KM
150µF, 6V POSCAP
Sanyo 6TPC150M
2 x 150µF, 4V POSCAP
Sanyo 4TPC150M
0.018Ω
Dale WSL2512-R018-F
7.0µH, 5.2A Ferrite
Sumida CEI122-H-7R0
5.6µH, 5.2A Ferrite
Sumida CEI122-H-5R6
The MAX8741/MAX8742 are dual, BiCMOS, switch-
mode power-supply controllers designed primarily for
buck-topology regulators in battery-powered applica-
tions where high-efficiency and low-quiescent supply
current are critical. Light-load efficiency is enhanced by
automatic idle-mode operation, a variable-frequency
pulse-skipping mode that reduces transition and gate-
charge losses. Each step-down, power-switching cir-
cuit consists of two n-channel MOSFETs, a rectifier,
and an LC output filter. The output voltage is the aver-
age AC voltage at the switching node, which is regulat-
ed 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 capacitor connected to BST_.
LOAD CURRENT
4A/500kHz
Detailed Description
7V to 24V
500kHz
Fairchild FDS6612A or
International Rectifier
IRF7807V
Fairchild FDS6670S or
International Rectifier
IRF7807DV1
4 x 10µF, 25V ceramic
Taiyo Yuden TMK432BJ106KM
2 x 150µF, 6V POSCAP
Sanyo 6TPC150M
2 x 220µF, 4V POSCAP
Sanyo 4TPC220M
0.012Ω
Dale WSL2512-R012-F
4.2µH, 6.9A Ferrite
Sumida CEI122-H-4R2
4.2µH, 6.9A Ferrite
Sumida CEI122-H-4R2
6A/500kHz