Datasheet

VIN
SW
DRIVER
PWM
RT
CLK
VCC
HV-LDO
EN
FB
GND
5k
COMP
MAX DUTY
SHUTDOWN
STANDBY
UVLO
CLK
(Leading Edge Blanking)
RAMP
S
R
Q
VCC
ENABLE
ENABLE
Disable
VCC
ENABLE
CS
CS
RAMP
CS
SLOPE COMP RAMP
450 mV
0
+
Disable
ENABLE
CLK
×
CURRENT
LIMIT
1.5V
1.3V
+5V
1.26V
CURRENT
SENSE
50 m:
1.26V
+5V
+6.9V
2.8V
0.45V
6 PA
REFERENCE
GENERATOR
Av = 30
0.7
THERMAL
STANDBY
(165
o
C)
OSCILLATOR
WITH
SYNC
CAPABILITY
1.26V
+
-
+
-
+
-
+
-
+
-
-
+
+
-
LM5001 , LM5001-Q1
SNVS484G –JANUARY 2007–REVISED APRIL 2014 www.ti.com
7 Detailed Description
7.1 Overview
The LM5001 high voltage switching regulator features all the functions necessary to implement an efficient boost,
flyback, SEPIC or forward current mode power converter. The operation can be best understood by referring to
the block diagram. At the start of each cycle, the oscillator sets the driver logic and turns on the power MOSFET
to conduct current through the inductor or transformer. The peak current in the MOSFET is controlled by the
voltage at the COMP pin. The COMP voltage increases with larger loads and decrease with smaller loads. This
voltage is compared with the sum of a voltage proportional to the power MOSFET current and an internally
generated Slope Compensation ramp. Slope Compensation is used in current mode PWM architectures to
eliminate sub-harmonic current oscillation that occurs with static duty cycles greater than 50%. When the
summed signal exceeds the COMP voltage, the PWM comparator resets the driver logic, turning off the power
MOSFET. The driver logic is then set by the oscillator at the end of the switching cycle to initiate the next power
period.
The LM5001 has dedicated protection circuitry to protect the IC from abnormal operating conditions. Cycle-by-
cycle current limiting prevents the power MOSFET current from exceeding 1 A. This feature can also be used to
soft-start the regulator. Thermal Shutdown circuitry holds the driver logic in reset when the die temperature
reaches 165°C, and returns to normal operation when the die temperature drops by approximately 20°C. The EN
pin can be used as an input voltage undervoltage lockout (UVLO) during start-up to prevent operation with less
than the minimum desired input voltage.
7.2 Functional Block Diagram
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Product Folder Links: LM5001 LM5001-Q1