MAX1641EEE+ Maxim Integrated Products, MAX1641EEE+ Datasheet - Page 9

• Manufacturer Part Number: MAX1641EEE+
• Description: IC SW-MODE CUR SOURCE ADJ 16QSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX1641EEE+

• Function: Charge Management
• Voltage - Supply: 5.5 V ~ 26 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP (0.150", 3.90mm Width)
• Number Of Outputs: 1
• Duty Cycle (max): 100 %
• Output Voltage: 2 V to 24 V
• Mounting Style: SMD/SMT
• Switching Frequency: 500 KHz
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Synchronous Pin: No
• Topology: Buck
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

where V
voltage.
When programming the off-time, consider such factors
as maximum inductor current ripple, maximum output
voltage, inductor value, and inductor current rating. The
output current ripple is less than the inductor current rip-
ple and depends heavily on the output capacitor’s size.
Perform the following steps to program the off-time:
1) Select the maximum output current ripple. I
2) Select the maximum output voltage. V
3) Calculate the inductor value range as follows:
4) Select an inductor value in this range.
5) Calculate t
6) Program t
7) Calculate the switching frequency by:
Note that R
trickle charge period.
The on-chip reference is laser trimmed for a precise 2V
at REF. REF can source no more than 50µA. Bypass
REF with a 0.1µF capacitor to ground.
The constant-current loop’s output is brought out at CC.
To reduce noise due to variations in switching currents,
bypass CC with a 1nF to 100nF capacitor to ground. A
large capacitor value maintains a constant average out-
put current but slows the loop response to changes in
switching current. A small capacitor value speeds up
the loop response to changes in switching current,
L
L
where t
t
age, V
peak-to-peak current ripple.
OFF
MIN
MAX
) / L. L is the inductor value, V
= (V
TERM
= (V
OUT
ON
Current Source with Synchronous Rectifier
TOFF
OUTMAX
OFF
OUTMAX
OFF
Constant-Current Loop: AC Loop
= (I
R
is the output voltage, and I
= 2V and V
TOFF
by selecting R
t
R
sets both the off-time and the pulse-
as follows:
fs = 1 / (t
OFF
_______________________________________________________________________________________
x L) / (V
= (29.3 x 10
x 1µs) / I
Programming the Off-Time
x 10µs) / I
=
V
OUTMAX
L x I
ON
IN
OUT
R
- V
R
+ t
TOFF
R
is the desired output
OUT
9
OFF
) x t
from:
)
) and I
Compensation
IN
Adjustable-Output, Switch-Mode
OFF
is the input volt-
OUT
R
Reference
is the output
R
(MAX)(V)
= (V
R
(A)
OUT
x
generating increased ripple at the output. Select C
Synchronous rectification reduces conduction losses in
the rectifier by shunting the Schottky diode with a low-
resistance MOSFET switch. In turn, efficiency increases
by about 3% to 5% at heavy loads. To prevent cross-
conduction or “shoot-through,” the synchronous rectifier
turns on shortly after the P-channel power MOSFET
turns off. The synchronous rectifier remains off for 90%
of the off-time. In low-cost designs, the synchronous
rectifier FET may be replaced by a Schottky diode.
The MAX1640/MAX1641 drive an enhancement-mode
P-channel MOSFET and a synchronous-rectifier N-
channel MOSFET (Table 2).
When selecting a P-channel FET, some important para-
meters to consider are on-resistance (r
mum drain-to-source voltage (V
gate-to-source voltage (V
threshold voltage (V
In high-current applications, MOSFET package power
dissipation often becomes a dominant design factor.
I 2 R power losses are the greatest heat contributor for
both high-side and low-side MOSFETs. Switching loss-
es affect the upper MOSFET only (P-channel), since the
Schottky rectifier or the N-FET body diode clamps the
switching node before the synchronous rectifier turns on.
Table 2. Component Manufacturers
to optimize the ripple vs. loop response.
Inductor
MOSFETs
Sense Resistor
Capacitors
Rectifier
COMPONENT
Sumida
Coilcraft
Coiltronics
International Rectifier
Siliconix
Dale
IRC
AVX
Sprague
Motorola
Nihon
TH
Synchronous Rectification
External Switching Transistors
min).
MANUFACTURER
Component Selection
GS
max), and minimum
DS
CDRH125 series
D03316P series
UP2 series
IRF7309
S14539DY
WSL-2010 series
LR2010-01 series
TPS series
595D series
MBAR5340t3
IN5817-IN5822
NSQ03A04
max), maximum
DS(ON)
), maxi-
CC
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