MIC22602YML TR Micrel Inc, MIC22602YML TR Datasheet - Page 15

• Manufacturer Part Number: MIC22602YML TR
• Description: ID BUCK SYNC ADJ 6A 24MLF
• Manufacturer: Micrel Inc
• Type: Step-Down (Buck), PWM - Voltage Moder

Specifications of MIC22602YML TR

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: Adj to 0.7V
• Current - Output: 6A
• Frequency - Switching: 1MHz
• Voltage - Input: 2.6 ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 24-MLF®, QFN
• Voltage - Supply: 2.6 V ~ 5.5 V
• Frequency-max: 1.2MHz
• Duty Cycle: 100%
• Pwm Type: Voltage Mode
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 576-3645-2; MIC22602YML TR; MIC22602YMLTR

An alternative method here shows an example of a V
& V
that POR is taken from Vo1 as POR
This is because POR is set high when FB > 0.9⋅V
this example, FB
Micrel, Inc.
October 2009
TT
solution for a DDR memory power supply. Note
2
is regulated to ½⋅V
REF
2
.
will not go high.
REF
DDQ
. In
15
Current Limit
The MIC22602 is protected against overload in two
stages. The first is to limit the current in the P-channel
switch; the second is over temperature shutdown.
Current is limited by measuring the current through the
high side MOSFET during its power stroke and
immediately switching off the driver when the preset limit
is exceeded.
The circuit in Figure 4 describes the operation of the
current limit circuit. Since the actual RDS
Channel MOSFET varies part-to-part, over temperature
and with input voltage, simple IR voltage detection is not
employed. Instead, a smaller copy of the Power
MOSFET (Reference FET) is fed with a constant current
which is a directly proportional to the factory set current
limit. This sets the current limit as a current ratio and
thus, is not dependant upon the RDS
limit is set to nominal value. Variations in the scale factor
K between the Power PFET and the reference PFET
used to generate the limit threshold account for a
relatively small inaccuracy.
Thermal Considerations
The MIC22602 is packaged in the MLF
package that has excellent thermal performance
equaling that of the larger TSSOP packages. This
maximizes heat transfer from the junction to the exposed
pad (ePAD) which connects to the ground plane. The
size of the ground plane attached to the exposed pad
determines the overall thermal resistance from the
junction to the ambient air surrounding the printed circuit
board. The junction temperature for a given ambient
temperature can be calculated using:
Where
•
T
P
package and is typically 1.5W at 6A load. This
has been calculated for a 1µH inductor and
details can be found in table 1 below for
reference.
J
DISS
= T
Figure 4. Current Limit Detail
AMB
is the power dissipated within the MLF
+ P
DISS
· Rθ
JA
ON
®
M9999-102809-A
4mm x 4mm, a
value. Current
ON
MIC22602
of the P-
®