LM26001QMXAX/NOPB National Semiconductor, LM26001QMXAX/NOPB Datasheet - Page 16

• Manufacturer Part Number: LM26001QMXAX/NOPB
• Description: IC REG SW 1.5A W/SLEEP 16-TSSOP
• Manufacturer: National Semiconductor
• Series: PowerWise®r
• Type: Step-Down (Buck)r

Specifications of LM26001QMXAX/NOPB

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.25 ~ 35 V
• Current - Output: 1.5A
• Frequency - Switching: 150kHz ~ 500kHz
• Voltage - Input: 4 ~ 38 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-TSSOP Exposed Pad, 16-eTSSOP, 16-HTSSOP
• Power - Output: 2.6W
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LM26001QMXAX

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Thermal Considerations and TSD
Although the LM26001 has a built in current limit, at ambient
temperatures above 80°C, device temperature rise may limit
the actual maximum load current. Therefore, temperature rise
must be taken into consideration to determine the maximum
allowable load current.
Temperature rise is a function of the power dissipation within
the device. The following equations can be used to calculate
power dissipation (PD) and temperature rise, where total PD
is the sum of FET switching losses, FET DC losses, drive
losses, Iq, and VBIAS losses:
PD
Psw
TOTAL
DC
= D x Iload
= Psw
P
QG
P
VBIAS
AC
= Vin x 4.6 x 10
P
+ Psw
2
Iq
= Vbias x I
x (0.2 + 0.00065 x (T
= Vin x Iq
DC
+ PQG + P
VBIAS
-9
x fsw
Iq
+ P
j
- 25))
VBIAS
16
Given this total power dissipation, junction temperature can
be calculated as follows:
Where θ
with a large copper plane area. θ
metallization area.
To calculate the maximum allowable power dissipation, as-
sume Tj = 125°C. To ensure that junction temperature does
not exceed the maximum operating rating of 125°C, power
dissipation should be verified at the maximum expected op-
erating frequency, maximum ambient temperature, and min-
imum and maximum input voltage. The calculated maximum
load current is based on continuous operation and may be
exceeded during transient conditions.
If the power dissipation remains above the maximum allow-
able level, device temperature will continue to rise. When the
junction temperature exceeds its maximum, the LM26001 en-
gages Thermal Shut Down (TSD). In TSD, the part remains
in a shutdown state until the junction temperature falls to with-
in normal operating limits. At this point, the device restarts in
soft-start mode.
JA
=38°C/W (typically) when using a multi-layer board
Tj = Ta + (PD
TOTAL
JA
varies with board type and
x θ
JA
)