LTC3613 Datasheet, PDF (10/36 Pages) Linear Technology – 24V, 15A Monolithic Step Down Regulator

LTC3613
FUNCTIONAL DIAGRAM
UVLO
3.65V
4.2V
SV_IN
IN
LDO
OUT EN
1.3μA
RUN
+
0.75V –
1.2V –
START
V_OUT
ONE-SHOT ^STOP
TIMER
LOGIC
CONTROL
TIME
ADJUST
CLOCK
RT
MODE/PLLIN
RT
CLOCK
DETECT
OSCILLATOR
PLL
SYSTEM
– ^ICMP +
– ^IREV +
1μA
INTV_CC
R_{PGD PGOOD}
0.645V
OV
0.6V
EA
(g_m(EA) = 1.7mS)
TG DRV
4.6V
BG DRV
DA
(A = 1)
PV_IN
BO0ST
D_B
MT
SW
EXTV_CC
INPUT SUPPLY
C_IN
C_B
L
R_SENSE
V_IN
C_IN
V_OUT
INTV_CC
MB
PGND
INTV_CC
C_VCC
C_OUT
R_FB2
R_FB1
SENSE⁺
SENSE^–
TRACK/SS
C_SS
V_OSNS+
V_OSNS–
3613 FD
UV
0.555V _VRNG
INTV_CC
R1
R2
ITH SGND
R_ITH
C_ITH1
OPERATION (Refer to Functional Diagram)
Main Control Loop
The LTC3613 uses valley current mode control to regulate
the output voltage in a monolithic, all N-channel MOSFET
DC/DC step-down converter. Current control is achieved by
sensing the inductor current across SENSE⁺ and SENSE^–,
either by using an explicit resistor connected in series with
the inductor or by implicitly sensing the inductor’s resis-
tive (DCR) voltage drop through an RC filter connected
across the inductor.
10
In normal steady-state operation, the top MOSFET is turned
on for a fixed time interval proportional to the delay in the
one-shot timer. The PLL system adjusts the delay in the
one-shot timer until the top MOSFET turn-on is synchro-
nized either to the internal oscillator or the external clock
input if provided. As the top MOSFET turns off, the bottom
MOSFET turns on with a small time delay (dead time) to
avoid shoot-through current. The next switching cycle is
initiated when the current comparator, I_CMP, senses that
inductor current has reached the valley threshold point
3613fa