Rainbow Electronics MAX15034 - Manual (Page 15)

MAX15034
MOSFET Gate Drivers (DH_, DL_)
The high-side drivers (DH1 and DH2) and low-side dri-
vers (DL1 and DL2) drive the gates of external n-channel
MOSFETs. The high-peak sink and source current capa-
bility of these drivers provides ample drive for the fast
rise and fall times of the switching MOSFETs. Faster rise
and fall times result in reduced switching losses. For low-
output, voltage-regulating applications where the duty
cycle is less than 50%, choose high-side MOSFETs (Q2
and Q4, Figure 6) with a moderate R
DS(ON) and a very
low gate charge. Choose low-side MOSFETs (Q1 and
Q3, Figure 6) with very low R
DS(ON) and moderate gate
charge. The driver block also includes a logic circuit that
provides an adaptive nonoverlap time (30ns typ) to pre-
vent shoot-through currents during transition. Figure 7
shows the dual-phase, single-output buck regulator.
2 x f SW (V/S)
RAMP
CLK
CSP_
CSN_
GM IN
EN_
1.225V
CLP_
V
DD
BST_
DH_
LX_
DL_
PGND
A V = 36V/V
PWM
COMPARATOR
S
R
Q
Q
g m = 500 μS
Figure 3. Current Comparator and MOSFET Driver Logic
LOAD
C OUT
V
OUT
V REF = 0.61V
R F
R 1
R
2
EAN_
EAOUT_
Figure 4. Voltage Error Amplifier
LOAD (A)
V CNTR
NO LOAD 1/2 LOAD FULL LOAD
VOL
TAGE-POSITIONING WINDOW
V CNTR + ΔV
OUT /2
V CNTR - ΔV
OUT /2
Figure 5. Defining the Voltage-Positioning Window
Configurable, Single-/Dual-Output, Synchronous
Buck Controller for High-Current Applications
______________________________________________________________________________________ 15