Datasheet

MAX17598/MAX17599
Low I
Q
, Wide-Input Range, Active Clamp
Current-Mode PWM Controllers
12Maxim Integrated
Pin Description (continued)
Detailed Description
The MAX17598/MAX17599 low I
Q
active-clamp current-
mode PWM controllers contain all the control circuitry
required for design of wide-input isolated/nonisolated for-
ward converter industrial power supplies. The MAX17598
has a rising UVLO threshold of 20V with a 13V hysteresis,
and is therefore well-suited for universal input (rectified
85V AC to 265V AC) or telecom (36V DC to 72V DC)
power supplies. The MAX17599 features a 4.1V rising
UVLO with a 200mV hysteresis and is optimized for low-
voltage industrial supplies (4.5V DC to 36V DC).
The devices include an AUX driver that drives an auxiliary
MOSFET (clamp switch) that helps implement the active-
clamp transformer reset topology for forward converters.
Such a reset topology has several advantages, including
reduced voltage stress on the switches, transformer size
reduction due to larger allowable flux swing, and improved
efficiency due to elimination of dissipative snubber circuit-
ry. Programmable dead time between the AUX and main
driver allows for zero voltage switching (ZVS).
Input Voltage Range
The MAX17598 has different rising and falling undervolt-
age lockout (UVLO) thresholds on the V
IN
pin than those
of the MAX17599. The thresholds for the MAX17598
are optimized for implementing power-supply startup
schemes typically used for off-line AC/DC and telecom
DC-DC power supplies that are typically encountered in
industrial applications. As such, the MAX17598 has no
limitation on the maximum input voltage, as long as the
external components are rated suitably, and the maxi-
mum operating voltages of the MAX17598 are respected.
The MAX17598 can be successfully used in universal
input (85V to 265V AC) rectified bus applications, recti-
fied 3-phase DC bus applications, and telecom (36V to
72V DC) applications.
The V
IN
pin of the MAX17599 has a maximum operating
voltage of 36V. The MAX17599 implements rising and
falling thresholds on the V
IN
pin that assume power-
supply startup schemes, typical of lower voltage DC-DC
applications down to an input voltage of 4.5V DC. Thus
isolated/non-isolated active-clamp converters with sup-
ply-voltage range of 4.5V to 36V can be implemented
with the MAX17599. See Startup Operation section
for more details on power-supply startup schemes for
MAX17598/MAX17599.
PIN NAME FUNCTION
11 NDRV External Switching NMOS Gate-Driver Output
12 AUXDRV
PMOS Active-Clamp-Switch Gate-Driver Output. AUXDRV can also be used to drive a pulse
transformer for synchronous flyback application.
13 V
DRV
Linear Regulator Output and Driver Input. Connect a 1FF bypass capacitor from V
DRV
to PGND as
close as possible to the IC.
14 V
IN
Internal V
DRV
Regulator Input. Connect V
IN
to the input voltage source. Bypass V
IN
to PGND with a
0.1FF minimum ceramic capacitor.
15 EN/UVLO
Enable/Undervoltage Lockout Pin. To externally program the UVLO threshold of the input supply,
connect a resistive divider among input supply, EN/UVLO, and SGND.
16 OVI
Overvoltage Comparator Input. Connect a resistive divider among the input supply, OVI, and SGND
to set the input overvoltage threshold.
— EP Exposed Pad