MIC2549A-2YN Micrel Inc, MIC2549A-2YN Datasheet - Page 13

• Manufacturer Part Number: MIC2549A-2YN
• Description: Programmable Current Limit High-Side Switch With Over-Temperature Latch ( )
• Manufacturer: Micrel Inc
• Type: High Sider

Specifications of MIC2549A-2YN

• Input Type: Non-Inverting
• Number Of Outputs: 1
• On-state Resistance: 35 mOhm
• Current - Peak Output: 3A
• Voltage - Supply: 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Through Hole
• Package / Case: 8-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output / Channel: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Applications Information
Supply Filtering
A 0.1 F to 1 F bypass capacitor from IN to GND, located
near the MIC2545A and MIC2549A, is strongly recommended
to control supply transients. Without a bypass capacitor, an
output short may cause sufficient ringing on the input (from
supply lead inductance) to damage internal control circuitry.
Input transients must not exceed the absolute maximum
supply voltage (V
Power Dissipation
The device's junction temperature depends on several fac-
tors such as the load, PCB layout, ambient temperature, and
package type. Equations that can be used to calculate power
dissipation and junction temperature are found below.
Calculation of power dissipation can be accomplished by the
following equation:
To relate this to junction temperature, the following equation
can be used:
where:
April 2004
MIC2545A/2549A
(+)
(–)
Bold lines indicate
0.1" wide, 1-oz. copper
high-current traces.
5V
4.7µF
V
D+
D–
GND
P
T
BUS
J
D
= P
= R
D
DS(on)
Figure 3. Supply Bypassing
LDO Regulator
JA
IN
MIC5203-3.3
IN
(max) = 6V) even for a short duration.
+ T
GND
(I
R
OUT
1
2
3
4
A
SET
MIC2549A-1BM
OUT
EN
FLG
GND
ILIM
)2
1.5k
2%
1.0
µF
OUT
OUT
IN
IN
4.0V to 5.5V
8
7
6
5
3.3V USB Controller
V+
D+
D–
OVERCURRENT
0.1µF to 1µF
10k
GND
Figure 4. USB Host Application
ON/OFF
0.1µF
13
R
SET
Transient Overcurrent Filter
The inrush current from the connection of a heavy capacitive
load may cause the fault flag to fall for 10 s to 200 s while the
switch is in a constant-current mode, charging the capaci-
tance.
Adding an optional series resistor-capacitor (R
lel with R
current-limit to be set to a different value than steady state. A
typical USB hot-plug inrush is 2A to 3A for 10 s to 20 s. If
R
1 F (RC 90 s) allows transient surge of 3A to pass for 90 s
without tripping the overcurrent flag (FLG).
USB Power Distribution
The MIC2545A is ideal for meeting USB power distribution
requirements. Figure 7 depicts a USB Host application. R
should be set to a value providing a current-limit >500mA.
The accurate current-limit of the MIC2545A will reduce power
supply current requirements. Also, fast reaction to short
circuit faults prevent voltage droop in mobile PC applications.
Printed Circuit Board Hot-Plug
The MIC2545A/49A is an ideal inrush current-limiter suitable
for hot-plug applications. Due to the integrated charge pump,
the MIC2545A/49A presents a high impedance when off and
slowly becomes a low impedance as it turns on. This “soft-
start” feature effectively isolates power supplies from highly
capacitive loads by reducing inrush current during hot-plug
events. Figure 5 shows how the MIC2545A may be used in
a hot-plug application.
EN
FLG
GND
ILIM
MIC2545A-2
SET
(optional)
R
T
T
is 435 (530mA), an R
C
SET(2)
JA
SET
J
A
OUT
OUT
= junction temperature
= ambient temperature
= is the thermal resistance of the package
SET
IN
IN
, as shown in Figure 4, allows the transient
0.1µF
120µF
SET2
Ferrite
Bead
0.01µF
of 88 (2.5A) and C
GND
V
BUS
D+
D–
SET2
M9999-041204
Downstream
500mA max.
) in paral-
4.75V min.
Port 1
USB
SET
Micrel
SET
of