EL7556BCM-T13 INTERSIL [Intersil Corporation], EL7556BCM-T13 Datasheet - Page 11

• Manufacturer Part Number: EL7556BCM-T13
• Description: Integrated Adjustable 6 Amp Synchronous Switcher
• Manufacturer: INTERSIL [Intersil Corporation]

Operating frequency can be adjusted through the C
or can be driven by an external clock source. If the oscillator
is driven by an external source, care must be taken in the
selection of C
determine the open loop gain of the system, changes to
C
maintain a constant gain ratio. The recommended ratio of
C
Temperature Sensor
An internal temperature sensor continuously monitors die
temperature. In the event that die temperature exceeds the
thermal trip-point, the OT pin will output a logic 0. The upper
and lower trip points are set to 135°C and 100°C
respectively. To enable thermal shutdown this pin should be
tied directly to OUTEN. Use of this feature is recommended
during normal operation.
Power Good and Power On Reset
During power up the output regulator will be disabled until
V
500mV of hysteresis is present to eliminate noise induced
oscillations.
Under-voltage and over-voltage conditions on the regulator
output are detected through an internal window comparator.
A logic 1 on the PWRGD output indicates that regulated
output voltage is within ±10% of the nominally programmed
output voltage. Although small, the typical values of the
PWRGD threshold will vary with changes to external
feedback (and resultant loop gain) of the system. This
dependence is shown in the typical performance curves.
Thermal Management
The EL7556B utilizes “fused lead” packaging technology in
conjunction with the system board layout to achieve a lower
thermal resistance than typically found in standard 28-pin
SO packages. By fusing (or connecting) multiple external
leads to the die substrate within the package, a very
conductive heat path to the outside of the package is
created. This conductive heat path MUST then be connected
to a heat sinking area on the PCB in order to dissipate heat
out and away from the device. The conductive paths for the
EL7556B package are the fused leads: # 7, 9, 10, 11, 12, 18,
and 19. If a sufficient amount of PCB metal area is
connected to the fused package leads, a junction-to-ambient
thermal resistance of approximately 31°C/W can be
achieved (compared to 78°C/W for a standard SO28
package). The general relationship between PCB heat-
sinking metal area and the thermal resistance for this
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OSC
OSC
IN
reaches a value of approximately 4.0V. Approximately
require corresponding changes to C
to C
SLOPE
SLOPE
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is 1.5:1
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
. Since the C
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11
OSC
and C
SLOPE
SLOPE
in order to
OSC
values
pin
EL7556B
package is shown in the Performance Curves section of this
data sheet. It can be readily seen that the thermal resistance
for this package approaches an asymptotic value of
approximately 31°C/W without any airflow. Additional
information can be found in Application Note #8 (Measuring
the Thermal Resistance of Power Surface-Mount Packages).
If the thermal shutdown pin is connected to OUTEN the IC
will enter thermal shutdown when the maximum junction
temperature is reached. For a thermal shutdown of 135°C
and power dissipation of 2.2W the ambient temperature is
limited to a maximum value of 67°C (typical). The ambient
temperature range can be extended with the application of
air flow. For example, the addition of 100LFM reduces the
thermal resistance by approximately 15% and can extend
the operating ambient to 77°C (typical). Since the thermal
performance of the IC is heavily dependent on the board
layout, the system designer should exercise care during the
design phase to ensure that the IC will operate under the
worst-case environmental conditions.