参数资料
型号: LM27402SQ
厂商: NATIONAL SEMICONDUCTOR CORP
元件分类: 稳压器
英文描述: SWITCHING CONTROLLER, 1350 kHz SWITCHING FREQ-MAX, QCC16
封装: 4 X 4 MM, 0.80 MM HEIGHT, 0.65 MM PITCH, LLP-16
文件页数: 23/32页
文件大小: 653K
代理商: LM27402SQ
Pin Descriptions
eTSSOP Pin
#
LLP Pin #
Name
Description
1
16
CS+
Non-inverting input to the current sense comparator.
2
15
CS-
Inverting input to the current sense comparator with +10 A offset current for
adjustable current limit setpoint.
3
1
SS/TRACK
Soft-start or tracking input. A startup rate can be defined with the use of an
external soft-start capacitor from SS/TRACK to GND. A +3 A current source
charges the soft-start capacitor to set the output voltage rise time during startup.
SS/TRACK can also be controlled with an external voltage source for tracking.
SS/TRACK should not exceed the voltage on VDD.
4
2
FB
Inverting input to the error amplifier to set the output voltage and compensate
the voltage mode control loop.
5
3
COMP
Output of the internal error amplifier. The COMP voltage is compared to an
internally generated ramp of the PWM comparator to establish the duty cycle
command.
6
4
FADJ
Frequency adjust pin. The switching frequency can be set to a predetermined
rate by connecting a resistor between FADJ and GND.
7
6
SYNC
Frequency synchronization pin. An external clock signal can be applied to SYNC
to set the switching frequency. The SYNC frequency must be greater than the
frequency set by the FADJ pin. If the signal is not present, the switching
frequency will decrease to the frequency set by the FADJ resistor. SYNC should
not exceed the voltage on VDD and should be grounded if not used.
8
5
EN
LM27402 enable pin. Apply a voltage typically higher than 1.17V to EN and the
LM27402 will begin to switch if VIN and VDD have exceeded the UVLO voltage.
A hysteresis of 100 mV on EN provides noise immunity. EN is internally tied to
VDD through a 2 A pullup current source. EN should not exceed the voltage on
VDD.
9
8
PGOOD
Power good output flag. PGOOD is connected to the drain of a pulldown FET.
The PGOOD pin is typically connected to VDD through a pull-up resistor.
10
7
VIN
Input supply rail. The VIN operating range is 3V to 20V and is connected to the
input rail through an RC filter.
11
9
GND
Common ground.
12
10
VDD
Internal sub-regulated 4.5V bias supply. VDD is used to supply the voltage on
CBOOT to facilitate high-side FET switching. Connect a 1 F ceramic capacitor
from VDD to GND as close as possible to the LM27402. VDD cannot be
connected to a separate voltage rail. However, VDD can be connected to VIN to
provide increased gate drive only if V
IN 5.5V. A 1, 1 F input filter can be used
for increased noise rejection.
13
11
LG
Low-side N-FET gate drive.
14
12
SW
Switch-node connection and return path for the high-side gate driver.
15
14
HG
High-side N-FET gate drive.
16
13
CBOOT
High-side gate driver supply rail. Connect a ceramic capacitor from CBOOT to
SW and a Schottky diode from VDD to CBOOT.
EP
Exposed Pad. The EP must be connected to GND but cannot be used as the
primary ground connection. Use multiple vias under this pad for optimal thermal
performance.
3
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LM27402
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