Typical operating circuit, Layout considerations – Rainbow Electronics MAX5929 User Manual
Page 22
MAX5927/MAX5929
Layout Considerations
To take full tracking advantage of the switch response
time to an output fault condition, it is important to keep all
traces as short as possible and to maximize the high-cur-
rent trace dimensions to reduce the effect of undesirable
parasitic inductance. Place the MAX5927/MAX5929 close
to the card’s connector. Use a ground plane to minimize
impedance and inductance. Minimize the current-sense
resistor trace length (<10mm), and ensure accurate cur-
rent sensing with Kelvin connections (Figure 13).
When the output is short circuited, the voltage drop
across the external MOSFET becomes large. Hence, the
power dissipation across the switch increases, as does
the die temperature. An efficient way to achieve good
power dissipation on a surface-mount package is to lay
out two copper pads directly under the MOSFET pack-
age on both sides of the board. Connect the two pads
to the ground plane through vias, and use enlarged
copper mounting pads on the topside of the board.
Low-Voltage, Quad, Hot-Swap
Controllers/Power Sequencers
22
______________________________________________________________________________________
MAX5927
MAX5929
GND
Q4
Q3
Q2
Q1
V
1
ON1
ON2
ON3
ON4
GND
ON1
OUT1
OUT2
*MAX5927 ONLY.
**OPTIONAL COMPONENT.
OUT3
OUT4
1nF
16V
STAT1
STAT2
STAT3
STAT4
LIM4*
BIAS
TIM
MODE
POL*
LA
TCH*
LIM3*
LIM2*
LIM1*
IN4
IN3
IN2
IN1
SENSE4
SENSE3
SENSE2
SENSE1
GA
TE1
GA
TE2
GA
TE3
GA
TE4
ON2
ON3
ON4
REMOVABLE CARD
BACKPLANE
V
2
V
3
V
4
R
SENSE1
R
SENSE2
R
SENSE3
R
SENSE4
R
LIM1
**
R
LIM2
**
R
LIM3
**
R
LIM4
**
R
LIM
**
Typical Operating Circuit
Figure 13. Kelvin Connection for the Current-Sense Resistors
SENSE RESISTOR
HIGH-CURRENT PATH
MAX5927
MAX5929