max5051auit Maxim Integrated Products, Inc., max5051auit Datasheet - Page 10

• Manufacturer Part Number: max5051auit
• Description: Max5051 Parallelable, Clamped Two-switch Power-supply Controller Ic
• Manufacturer: Maxim Integrated Products, Inc.

Parallelable, Clamped Two-Switch
Power-Supply Controller IC
10
PIN
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
______________________________________________________________________________________
STARTUP
XFRMRH
SYNCIN
DRVDD
FLTINT
NAME
PGND
DRVB
DRVH
UVLO
DRVL
AVIN
GND
LXH
LXL
BST
CS
Synchronous-Pulse Transformer Driver, PMOS Open Drain. LXH is the high-side driver for the secondary-
side synchronous-pulse transformer. LXH can also drive a high-speed switching optocoupler. If not
used, connect LXH to LXVDD.
Synchronous-Pulse Transformer Driver, NMOS Open Drain. LXL is the low-side driver for the secondary-
side synchronous-pulse transformer. LXL can also drive a high-speed switching optocoupler. If not used,
connect LXL to PGND.
Current-Sense Input. The current-limit threshold is internally set to 156mV relative to PGND. The device
has an internal noise filter. If necessary, connect an additional external RC filter.
Gate-Drive Output for Low-Side MOSFET. DRVL is capable of sourcing and sinking approximately 2A
peak current.
Power Ground
Supply Input for Low-Side MOSFET Driver. Bypass DRVDD locally with good quality 1µF || 0.1µF ceramic
capacitors. DRVDD is normally connected to REG9.
Gate-Drive Output for Boost MOSFET. Connect the gate of a small high-voltage external FET to this pin to
enable charging of the high-side boost capacitor connected between pins 20 and 22. This FET may be
necessary to keep the boost capacitor charged at light loads.
Transformer Input. Transformer primary high-side connection.
Gate-Drive Output for High-Side MOSFET
Boost Input. Boost supply connection point for the high-side MOSFET driver. Connect at least a 1µF ||
0.1µF ceramic capacitor from BST to XFRMRH with short and wide PC board traces. If the voltage across
the boost capacitor falls below the high-side undervoltage lockout threshold, the DRVH output stops
switching.
Supply Voltage Input. Connect AVIN directly to the input supply line.
Analog Signal Ground
Undervoltage Lockout Input. An external voltage-divider from the input supply sets the startup voltage;
the threshold is 1.24V with 130mV hysteresis. UVLO can also be used as a shutdown input. If unused,
connect UVLO to REG5
Startup Input. STARTUP coordinates simultaneous startup of multiple units from faults, during initial turn-
on, and UVLO recovery. When paralleling the secondaries of two MAX5051’s, the STARTUP inputs of
each device must be connected together.
Faul t Integ r ati on Inp ut. D ur i ng p er si stent cur r ent- l i m i t faul ts, a cap aci tor connected to FLTIN T i s char g ed
w i th an i nter nal 90µA cur r ent sour ce. S w i tchi ng i s ter m i nated w hen the vol tag e r eaches 2.9V . An exter nal
r esi stor connected i n p ar al l el d i schar g es the cap aci tor . S w i tchi ng r esum es w hen the vol tag e d r op s to 2V .
Synchronization Input. SYNCIN accepts the synchronization signal from SYNCOUT of another MAX5051
and shifts the switching of the synchronized unit by 180° allowing the reduction of input bypass
capacitors. The MAX5051 switches at the same frequency at SYNCIN. SYNCIN must be 50% duty cycle.
Leave SYNCIN floating if unused.
FUNCTION
Pin Description (continued)