MAX17009GTL+T Maxim Integrated Products, MAX17009GTL+T Datasheet - Page 34

• Manufacturer Part Number: MAX17009GTL+T
• Description: IC CTLR VIDEO SERIAL DUAL 40TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX17009GTL+T

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX17009 features a thermal-fault protection cir-
cuit. When the junction temperature rises above
+160°C, a thermal sensor sets the fault latch and shuts
down, immediately forcing DH and DL low, without
going through the soft-shutdown sequence. Toggle
SHDN or cycle the V
clear the fault latch and reactivate the controller after
the junction temperature cools by 15°C.
The DH and DL drivers are optimized for driving mode-
rate-sized high-side and larger low-side power
MOSFETs. This is consistent with the low duty factor
seen in notebook applications where a large V
differential exists. The high-side gate drivers (DH)
source and sink 2.2A, and the low-side gate drivers
(DL) source 2.7A and sink 8A. This ensures robust gate
drive for high-current applications. The DH floating
high-side MOSFET drivers are powered by internal
boost switch charge pumps at BST, while the DL syn-
chronous-rectifier drivers are powered directly by the
5V bias supply (V
Adaptive dead-time circuits monitor the DL and DH dri-
vers and prevent either FET from turning on until the
other is fully off. The adaptive driver dead time allows
operation without shoot-through with a wide range of
MOSFETs, minimizing delays and maintaining efficiency.
There must be a low-resistance, low-inductance path
from the DL and DH drivers to the MOSFET gates for
the adaptive dead-time circuits to work properly; other-
wise, the sense circuitry in the MAX17009 interprets the
MOSFET gates as “off” while charge actually remains.
Use very short, wide traces (50 mils to 100 mils wide if
the MOSFET is 1in from the driver).
The internal pulldown transistor that drives DL low is
robust, with a 0.25Ω (typ) on-resistance. This helps pre-
vent DL from being pulled up due to capacitive cou-
pling from the drain to the gate of the low-side
MOSFETs when the inductor node (LX) quickly switch-
es from ground to V
ages and long inductive driver traces may require
rising LX edges that do not pull up the low-side
MOSFETs’ gate, causing shoot-through currents. The
capacitive coupling between LX and DL created by the
MOSFET’s gate-to-drain capacitance (C
source capacitance (C
board parasitics should not exceed the following mini-
mum threshold:
AMD Mobile Serial VID Dual-Phase
Fixed-Frequency Controller
34
______________________________________________________________________________________
DD
IN
).
. Applications with high input volt-
CC
ISS
power supply below 0.5V to
MOSFET Gate Drivers
Thermal-Fault Protection
- C
RSS
), and additional
RSS
), gate-to-
IN
- V
OUT
Typically, adding a 4700pF between DL and power
ground (C
MOSFETs, greatly reduces coupling. Do not exceed
22nF of total gate capacitance to prevent excessive
turn-off delays.
Alternatively, shoot-through currents can be caused by
a combination of fast high-side MOSFETs and slow low-
side MOSFETs. If the turn-off delay time of the low-side
MOSFET is too long, the high-side MOSFETs can turn
on before the low-side MOSFETs have actually turned
off. Adding a resistor less than 5Ω in series with BST
slows down the high-side MOSFET turn-on time, elimi-
nating the shoot-through currents without degrading
the turn-off time (R
high-side MOSFET also reduces the LX node rise time,
thereby reducing EMI and high-frequency coupling
responsible for switching noise.
Figure 9. Gate Drive Circuit
(R
(C
BST
NL
)* OPTIONAL—THE CAPACITOR REDUCES LX TO DL CAPACITIVE
)* OPTIONAL—THE RESISTOR LOWERS EMI BY DECREASING THE
SWITCHING NODE RISE TIME.
COUPLING THAT CAN CAUSE SHOOT-THROUGH CURRENTS.
NL
in Figure 9), close to the low-side
V
PGND
GS TH
BST
V
DH
BST
DL
LX
DD
(
in Figure 9). Slowing down the
)
C
(R
>
BYP
(C
BST
C
V
NL
BST
IN
)*
)*
⎛
⎜
⎝
C
C
RSS
ISS
⎞
⎟
⎠
N
N
H
L
INPUT (V
L
IN
)