MAX8552 MAXIM [Maxim Integrated Products], MAX8552 Datasheet - Page 7

• Manufacturer Part Number: MAX8552
• Description: High-Speed, Wide-Input, Single-Phase MOSFET Driver
• Manufacturer: MAXIM [Maxim Integrated Products]

The MAX8552 single-phase gate driver, along with the
MAX8524/MAX8525 multiphase controllers, provide
flexible one- to eight-phase CPU core-voltage supplies.
The 1.0 /1.3
put current per phase. Each MOSFET driver in the
MAX8552 is capable of driving 3000pF capacitive
loads with only 12ns propagation delay and 11ns (typ)
rise and fall times, allowing operation up to 1.2MHz per
phase. Adaptive dead time controls MOSFET turn-on,
and user-programmable dead time provides additional
flexibility for high-side MOSFET turn-on. This maximizes
converter efficiency, while allowing operation with a vari-
ety of MOSFETs and PWM-controller ICs. An undervolt-
age-lockout circuit allows proper power-on sequencing.
The PWM signal input is both TTL and CMOS compati-
ble. An enable input allows total driver shutdown
(<0.1µA typ) for power-sensitive portable applications.
The high-side driver (DH) has a 1.3
resistance and 0.7
peak sourcing current and 7A peak sinking current with
a 5V supply voltage. The low-side driver (DL) has a typ-
ical 1.0
tance, yielding 5A peak sourcing current and 10A peak
sinking current. This reduces switching losses, making
the MAX8552 ideal for both high-frequency and high-
output-current applications.
The MAX8552 incorporates adaptive shoot-through pro-
tection for the switching transition after the high-side
MOSFET turns off and before the low-side MOSFET turns
on and vice versa. The low-side driver turns on only
when the LX voltage falls below 2.4V. Furthermore, the
delay time between the low-side MOSFET turn-off and
high-side MOSFET turn-on can be adjusted by selecting
the value of R1 (see the R
When V
and DL are held low. Once V
threshold and while PWM is low, DL is driven high and
DH is driven low. This prevents the output of the con-
verter from rising before a valid PWM signal is applied.
When EN is low, the MAX8552 is in shutdown mode
and the total input current is reduced to less than 1µA
for power-sensitive applications. In shutdown mode,
both DH and DL are held low. When EN goes high, the
MAX8552 becomes active.
CC
sourcing resistance and 0.5
is below the UVLO threshold (3.5V typ), DH
driver resistance allows up to 30A out-
MOSFET Gate Drivers (DH, DL)
Shoot-Through Protection and
_______________________________________________________________________________________
Programmable Delay (t
sinking resistance, resulting in 4A
Detailed Description
DLY
Undervoltage Lockout
Selection section).
CC
is above the UVLO
(typ) sourcing
sinking resis-
Single-Phase MOSFET Driver
DLY
EN
)
High-Speed, Wide-Input,
V
circuits. Bypass V
PGND and a 0.47µF or larger capacitor to GND to limit
noise to the internal circuitry. Connect these bypass
capacitors as close to the IC as possible.
The MAX8552 uses a bootstrap circuit to generate the
necessary drive voltage (V
high-side N-MOSFET. The selected high-side MOSFET
determines appropriate boost capacitance values (C6
in the Typical Application Circuit, Figure 1), according
to the following equation:
where Q
MOSFET and V
the high-side MOSFET driver. Choose V
0.2V when determining C
tor should be a low-equivalent series resistance (ESR)
ceramic capacitor.
Connect DLY to V
function and default to the adaptive delay time. To pro-
gram a longer specific delay time between the low-side
MOSFET driver turn-off and the high-side MOSFET turn-
on, connect a delay resistor, R
GND (R1 in the Typical Application Circuit, Figure 1).
See the Typical Operating Characteristics to select R
At high input voltages, fast turn-on of the high-side MOSFET
can momentarily turn on the low-side MOSFET due to the
high dV/dt appearing at the drain of the low-side MOSFET.
The high dV/dt causes a current flow through the Miller
capacitance (C
of the low-side MOSFET. Improper selection of the low-
side MOSFET that results in a high ratio of C
makes the problem more severe. To avoid this prob-
lem, minimize the ratio of C
low-side MOSFET. Adding a 1
and C
Similarly, adding a small capacitor from the gate to the
source of the high-side MOSFET has the same effect.
However, both methods work at the expense of
increased switching losses.
CC
provides the supply voltage for the internal logic
BST
GATE
can slow the high-side MOSFET turn-on.
Boost Flying-Capacitor Selection
is the total gate charge of the high-side
Applications Information
RSS
C
BST
CC
CC
BST
) and the input capacitance (C
to disable the programmable delay
is the voltage variation allowed on
with a 2.2µF or larger capacitor to
= Q
Avoiding dV/dt Turning on
BST
GATE
the Low-Side MOSFET
RSS
DH
. The boost flying-capaci-
/C
/ V
Decoupling of V
DLY
) to fully enhance the
ISS
resistor between BST
, between DLY and
BST
R
when selecting the
DLY
BST
Selection
= 0.1V to
RSS
/C
DLY
ISS
CC
ISS
7
.
)