Datasheet

TSSOP28
VIN
PGND
LO1
VCC
LO2
SR2
SR1
HS2
HO2
BST2
HS1
BST1
HO1
COMP
RD2
UVLO
OVP
CS
RAMP
SSSR
AGND
SLOPE
RT
REF
RD1
SS
SS OFF
RES
5 mm x 5 mm
WQFN 28
SS
RES
HS2 HO2 BST2
SSSR
REF
RT
SLOPE
RD2
COMP
AGND
RD1
PGND
LO1
VCC
LO2
BST1
SS OFF
SR1
OVP
RAMP
UVLO
CS
HS1
HO1
VIN
SR2
LM5046
SNVS703G –FEBRUARY 2011–REVISED MARCH 2013 www.ti.com
Connection Diagram
Figure 1. TSSOP28 Top View Figure 2. WQFN-28 Package Top View
PIN DESCRIPTIONS
TSSOP WQFN
Name Description Application Information
Pin Pin
1 25 UVLO Line Under-Voltage Lockout An external voltage divider from the power source sets the
shutdown and standby comparator levels. When UVLO reaches the
0.4V threshold the VCC and REF regulators are enabled. At the
1.25V threshold, the SS pin is released and the controller enters the
active mode. Hysteresis is set by an internal current sink that pulls
20µA from the external resistor divider.
2 26 OVP/OTP Over Voltage Protection An external voltage divider from the input power supply sets the
shutdown level during an over-voltage condition. Alternatively, an
external NTC thermistor voltage divider can be used to set the
shutdown temperature. The threshold is 1.25V. Hysteresis is set by
an internal current that sources 20 µA of current into the external
resistor divider.
3 27 RAMP Input to PWM Comparator Modulation ramp for the PWM comparator. This ramp can be a
signal representative of the primary current (current mode) or
proportional to the input voltage (feed-forward voltage mode). This
pin is reset to GND at the end of every cycle.
4 28 CS Current Sense Input If CS exceeds 750mV the PWM output pulse will be terminated,
entering cycle-by-cycle current limit. An internal switch holds CS low
for 40nS after either output switches high to blank leading edge
transients.
5 1 SLOPE Slope Compensation Current A ramping current source from 0 to 100µA is provided for slope
compensation in current mode control. This pin can be connected
through an appropriate resistor to the CS pin to provide slope
compensation. If slope compensation is not required, SLOPE must
be tied to ground.
6 2 COMP Input to the Pulse Width Modulator An external opto-coupler connected to the COMP pin sources
current into an internal NPN current mirror. The PWM duty cycle is
at maximum with zero input current, while 1mA reduces the duty
cycle to zero. The current mirror improves the frequency response
by reducing the AC voltage across the opto-coupler.
2 Submit Documentation Feedback Copyright © 2011–2013, Texas Instruments Incorporated
Product Folder Links: LM5046