LTC3824EMSE-PBF LINER [Linear Technology], LTC3824EMSE-PBF Datasheet - Page 6

• Manufacturer Part Number: LTC3824EMSE-PBF
• Description: High Voltage Step-Down Controller With 40?A Quiescent Current
• Manufacturer: LINER [Linear Technology]

BLOCK DIAGRAM
LTC3824
APPLICATIONS INFORMATION
Operation
The LTC3824 is a constant frequency current mode buck
controller with programmable switching frequency up to
600kHz.
Referring to the Block Diagram, the LTC3824’s basic
functions include a transconductance amplifi er gm to
regulate the output voltage and control the current mode
PWM current loop, the necessary logic to control the
PWM switching cycles, a high speed gate driver to drive
an external high power P-channel MOSFET and a voltage
regulator to bias the gate driver circuit.
6
R
FREQ
SYNC/
MODE
R
GND
SET
1.8V
+
100k
1.5V
+
–
1.1V
SHUTDOWN
OPERATION
Burst Mode
CONTROL
M2
+
2.5V
SS
50pF
0.3μA
+
–
OSC
+
Y6
2V
+
–
–
+
Y1
+
0.025V
S
Q
OR1
R
Burst Mode
DISABLE
PWM
Y2
0.1V
–
–
+
+
+
Y3
SENSE
R3
In normal operation each switching cycle starts with switch
turn-on and the inductor current is sampled through the
current sense resistor. This current is amplifi ed and then
compared to the error amplifi er output V
switch off. Voltage loop regulates the output voltage to the
programmed level through the output resistor divider and
the error amplifi er. Amplifi er E1 regulates the gate drive
low to approximately 8V below V
9V, and C
lower than 9V, gate drive high will be within 0.5V of V
and gate drive low within 1V of ground.
Important features include shutdown, current limit, soft-
start, synchronization and low quiescent current.
V
R2
R1
2k
C
C1
470pF
2.5V
GM
REFERENCE
SLOPE
COMP
50KHz FOLDBACK
SYNC DISABLE
–
+
V
REF
CAP
SS
D4
C
0.1μF
SS
stabilizes the voltage. Note that when V
D6
D7
6μ
+
E1
8V
Y5
+
–
B1
V
0.8V
2.5V
REF
+
M1
0.5V
GATE
V
CAP
FB
CC
C
0.1μF
CC
CAP
D1
R
S
for V
Q1
C2
V
L
IN
CC
C
RF2
higher than
to turn the
3824 BD
RF1
C
CC
V
3824fc
OUT
OUT
CC
is