MAX5069 Maxim Integrated, MAX5069 Datasheet - Page 10

• Manufacturer Part Number: MAX5069
• Description: High-Frequency / Current-Mode PWM Controller with Accurate Oscillator and Dual FET Drivers
• Manufacturer: Maxim Integrated

The MAX5069 features an input voltage UVLO/EN func-
tion to enable the PWM controller before any operation
can begin. The MAX5069A/D shut down if the voltage
at UVLO/EN falls below its 1.18V threshold. The
MAX5069B/C also incorporate a UVLO hysteresis input
to set the desired turn-off voltage.
The MAX5069A/D have an input voltage UVLO/EN with
a 1.231V threshold. Before any operation can com-
mence, the UVLO/EN voltage must exceed the 1.231V
threshold. The UVLO circuit keeps the PWM compara-
tor, ILIM comparator, oscillator, and output drivers shut-
down to reduce current consumption (see the
Functional Diagram).
High-Frequency, Current-Mode PWM Controller
with Accurate Oscillator and Dual FET Drivers
Figure
10
______________________________________________________________________________________
1. Nonisolated Power Supply with Programmable Input Supply Voltage
V
MAX5069A/D UVLO Adjustment
IN
R2
C2
C3
C4
C5
R3
R4
Undervoltage Lockout
FLTINT
V
REG5
RT
DT
SCOMP
AGND PGND
CC
C1
MAX5069B
IN
UVLO/EN
R1
COMP
NDRVB
NDRVA
HYST
CS
FB
R5
C6
R6
R
R7
HYST
D3
Q1
R8
Calculate R6 in
where V
and V
value in the 20kΩ range.
After a successful startup, the MAX5069A/D shut down
if the voltage at UVLO/EN drops below its 1.18V fall-
ing threshold.
In addition to programmable undervoltage lockout dur-
ing startup, the MAX5069B/C incorporate a UVLO/EN
ON
Q2
ULR2
is the desired startup voltage. Choose an R7
D1
D2
is the UVLO/EN’s 1.231V rising threshold
R
Figure
6
=
⎛
⎜
⎝
2 by using the following formula:
V
V
ULR
ON
2
Programmable Hysteresis
MAX5069B/C UVLO with
−
V
R9
R10
OUT
1
⎞
⎟ ×
⎠
C7
R
7