MAX5953A MAXIM [Maxim Integrated Products], MAX5953A Datasheet - Page 11

• Manufacturer Part Number: MAX5953A
• Description: IEEE 802.3af PD Interface and PWM Controllers with Integrated Power MOSFETs
• Manufacturer: MAXIM [Maxim Integrated Products]

IEEE 802.3af PD Interface and PWM Controllers
26, 27
28, 29
31, 32
33, 34
PIN
25
30
36
37
39
40
41
42
43
44
45
—
______________________________________________________________________________________
DCUVLO
REGOUT
XFRMRH
XFRMRL
INBIAS
FLTINT
DRVIN
NAME
OPTO
DRNH
RAMP
RTCT
RCFF
HVIN
SRC
BST
EP
PWM Comparator Inverting Input. OPTO is referenced to GND. Connect the collector of the
optotransistor to OPTO and a pullup resistor to REGOUT.
Source Connection of Low-Side Power MOSFET in the Two-Switch Power Stage of the DC-
DC Converter. Connect SRC to PGND with a low-value resistor for current limiting.
Low-Side Connection for the Isolation Transformer. Drain terminal of low-side power
MOSFET in the two-switch power stage of the DC-DC converter.
Supply Input for the Gate-Driver of Internal Power MOSFETs. DRVIN is referenced to
PGND. Bypass DRVIN with at least 0.1µF to PGND. Connect DRVIN to REGOUT.
High-Side Connection for the Isolation Transformer. Source connection of high-side power
MOSFET in the two-switch power stage of the DC-DC converter.
Drain Connection of High-Side MOSFET in the Two-Switch Power Stage of the DC-DC
Converter. Connect DRNH to the most positive rail of the input supply. Bypass DRNH
appropriately to handle the heavy switching current through the transformer.
Boost Input for the DC-DC Converter. BST is the boost connection point for the high-side
MOSFET driver. Connect a minimum 0.1µF capacitor from BST to XFRMRH with short and
wide PC board traces.
DC-DC Converter Undervoltage Lockout Input. DCUVLO is referenced to GND. Connect a
resistor-divider from HVIN to DCUVLO to GND to set the UVLO threshold.
DC-DC Converter Positive Input Power Supply. HVIN is referenced to GND. Connect HVIN
to V+.
Input from the Rectified Bias Winding to the DC-DC Converter. INBIAS is referenced to
GND. INBIAS is the input to the internal linear voltage regulator (REGOUT).
Internal Regulator Output. REGOUT is used for the DC-DC converter gate driver. REGOUT
is referenced to GND. V
voltage above the DCUVLO threshold. Bypass REGOUT to GND with a minimum 2.2µF
ceramic capacitor.
Oscillator Frequency Set Input for the PWM Controller. RTCT is referenced to GND.
Connect a resistor from RTCT to REGOUT and a ceramic capacitor from RTCT to GND to
set the oscillator frequency.
Fault Integration Input for PWM Controller. FLTINT is referenced to GND. During persistent
current-limit faults, a capacitor connected to FLTINT is charged with an internal 80µA
current source. Switching is terminated when V
connected in parallel discharges the capacitor. Switching resumes when V
to 1.9V.
Feed-Forward Input for PWM Controller. RCFF is referenced to GND. To generate the PWM
ramp, connect a resistor from RCFF to HVIN and a capacitor from RCFF to GND.
Ramp Sense Input for PWM Controller. Connect RAMP to RCFF.
Exposed Paddle. EP is internally unconnected and must be connected to V
To improve power dissipation, solder the exposed paddle to a copper pad on the PC
board.
with Integrated Power MOSFETs
REGOUT
is always present as long as HVIN is powered with a
FUNCTION
Pin Description (continued)
FLTINT
reaches 2.7V. An external resistor
FLTINT
EE
externally.
drops
11