CS51413EDR8G ON Semiconductor, CS51413EDR8G Datasheet - Page 12

• Manufacturer Part Number: CS51413EDR8G
• Description: IC REG BUCK LV 1.5A SYNC 8SOIC
• Manufacturer: ON Semiconductor
• Type: Step-Down (Buck)r

Specifications of CS51413EDR8G

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Current - Output: 1.5A
• Frequency - Switching: 520kHz
• Voltage - Input: 4.5 ~ 40 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Mounting Style: SMD/SMT
• Primary Input Voltage: 40V
• No. Of Outputs: 1
• Output Current: 1.5A
• No. Of Pins: 8
• Operating Temperature Range: -40°C To +85°C
• Current Rating: 1.5A
• Filter Terminals: SMD
• Input Voltage Primary Max: 40V
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: CS51413EDR8GOS

Figure 17, and the benefit of the foldback frequency and
current limit is self−evident.
Thermal Considerations
necessary prior to the adoption of the regulator. The current
drawn by the IC includes quiescent current, predriver
current, and power switch base current. The quiescent
current drives the low power circuits in the IC, which
include comparators, error amplifier and other logic blocks.
Therefore, this current is independent of the switching
current and generates power equal to
where:
switch and is approximately equal to 12 mA in worst case.
During steady state operation, the IC draws this current from
the Boost pin when the power switch is on and then receives
it from the V
current always returns to the V
current goes out to the regulator’s output even when the
power switch is turned off, a minimum load is required to
prevent overvoltage in light load conditions. If the Boost pin
voltage is equal to V
dissipation due to predriver current can be calculated by
current divided by beta of the device. Beta of 60 is used here
to estimate the base current. The Boost pin provides the base
current when the transistor needs to be on.
A calculation of the power dissipation of the IC is always
I
The predriver current is used to turn on/off the power
The base current of a bipolar transistor is equal to collector
The power dissipated by the IC due to this current is
Figure 17. In Short Circuit, the Foldback Current and
Foldback Frequency Limit the Switching Current to
Q
= quiescent current.
Protect the IC, Inductor and Catch Diode
W DRV + 12 mA
IN
pin when the switch is off. The predriver
W BASE +
IN
W Q + V IN
+ V
O
when the switch is on, the power
(V IN * V O )
V O 2
V IN
SW
pin. Since the predriver
I Q
60
I S
V O 2
V IN
)
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12
where:
and conduction current contribute to the power loss of a
non−ideal switch. The power loss can be quantified as
where:
both high current and voltage during each switch transition.
This regulator has a 30 ns turn−off time and associated
power loss is equal to
not considered here.
ambient temperature, IC power dissipation and thermal
resistance of the package. The equation is shown as follows,
125°C to guarantee proper operation and avoid any damages
to the IC.
Using the BIAS Pin
notable at low load and high input voltage as will be
explained below.
when the BIAS pin is used. The circuitry shown is not the
actual implementation, but is useful in the explanation.
BIAS pin. When the BIAS pin is low, the logic turns P2 on
and current is routed to the internal bias circuitry from the
V
in
I
When the power switch turns on, the saturation voltage
V
The switching loss occurs when the switch experiences
The turn−on time is much shorter and thus turn−on loss is
The total power dissipated by the IC is sum of all the above
The IC junction temperature can be calculated from the
The maximum IC junction temperature shall not exceed
The efficiency savings in using the BIAS pin is most
Figure 18 will help to understand the increase in efficiency
Internal bias to the IC can be supplied via the V
BIAS
S
SAT
pin. Conversely, when the BIAS pin is high, the logic
W IC + W Q ) W DRV ) W BASE ) W SAT ) W S
V
= DC switching current.
in
= saturation voltage of the power switch which is
shown in Figure 12.
W S +
W SAT +
T J + W IC
I S
Figure 18.
V IN
2
V O
V IN
R qJA ) T A
I S
30 ns
P1
P2
V SAT
f S
Internal
in
BIAS
pin or the