MAX1627ESA-T Maxim Integrated Products, MAX1627ESA-T Datasheet - Page 9

• Manufacturer Part Number: MAX1627ESA-T
• Description: DC/DC Switching Controllers 5/3.3V or Adjustable 100% Duty Cycle
• Manufacturer: Maxim Integrated Products

Specifications of MAX1627ESA-T

• Number Of Outputs: 1
• Output Voltage: 1.3 V to 16 V
• Output Current: 3 A
• Input Voltage: 3 V to 16.5 V
• Mounting Style: SMD/SMT
• Package / Case: SOIC-8 Narrow
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C

least 100 times FB’s input bias current. Capacitor C
is used to compensate the MAX1627 for even switch-
ing. Values between 0pF and 330pF work for many
applications. See the Stability and MAX1627 Feedback
Compensation section for details.
The current-sense comparator limits the peak switching
current to V
the current-sense resistor and V
threshold. V
85mV to 115mV. Minimizing the peak switching current
will increase efficiency and reduce the size and cost of
external components. However, since available output
current is a function of the peak switching current, the
peak current limit must not be set too low.
Set the peak current limit above 1.3 times the maximum
load current by setting the current-sense resistor to:
Alternatively, select the current-sense resistor for 5V
and 3.3V output applications using the current-sense
resistor graphs in Figures 6a and 6b. The current-sense
resistor’s power rating should be 20% higher than:
Standard wire-wound resistors have an inductance
high enough to degrade performance, and are not rec-
ommended. Surface-mount (chip) resistors have very
little inductance and are well suited for use as current-
Figure 6a. MAX1626 5V-Operation Current-Sense Resistor
Graph
High-Efficiency, Step-Down DC-DC Controllers
R
POWER RATING (W)
1.0
0.5
1.5
3.5
3.0
2.5
2.0
CS
CS
0
Current-Sense-Resistor Selection
4.5
/R
R
is typically 100mV, but can range from
V
OUT
CS
SENSE
5V/3.3V or Adjustable, 100% Duty-Cycle,
_______________________________________________________________________________________
5.0
= 5V
=
5.5
INPUT VOLTAGE (V)
, where R
1.3 x I
6.0
V
CS(MIN)
=
OUT(MAX)
R
R
R
R
10
SENSE
SENSE
SENSE
SENSE
CS
V
SENSE
2
12
CS MAX
= 0.03
= 0.04
= 0.05
= 0.1
is the current-sense
R
CS
(
14
is the value of
)
16
R2
Figure 5. Adjustable-Output Operation Using the MAX1627
sense resistors. Power metal-strip resistors feature
1/2W and 1W power dissipation, 1% tolerance, and
inductance below 5nH. Resistance values between
10mΩ and 500mΩ are available.
The essential parameters for inductor selection are
inductance and current rating. The MAX1626/MAX1627
operate with a wide range of inductance values. In many
applications, values between 10µH and 68µH take best
advantage of the controller’s high switching frequency.
Calculate the minimum inductance value as follows:
where 2µs is the minimum on-time. Inductor values
between two and six times L
Figure 6b. MAX1626 3.3V-Operation Current-Sense Resistor
Graph
L
1.0
0.5
3.5
3.0
2.5
2.0
1.5
(MIN)
0
3.0
C
V
R2
OUT
3.5
=
= 3.3V
4.0
V+
INPUT VOLTAGE (V)
(MAX)
4.5
V
R2
R3
10
CS MIN
(MIN)
R
R
R
R
R
- V
Inductor Selection
SENSE
SENSE
SENSE
SENSE
CS
(
12
FROM
OUTPUT
OUT
TO FB
= 0.03
= 0.04
= 0.05
= 0.1
are recommended.
)
14
x
16
2
s
9