Rainbow Electronics MAX14528 - Manual (Page 6)

MAX14527/MAX14528
Internal Switch
The MAX14527/MAX14528 incorporate an internal FET
with a 100mΩ (typ) R
ON . The FET is internally driven by
a charge pump that generates a necessary gate volt-
age above IN. The internal FET is capable of passing
more than 5A inrush current.
Overvoltage Lockout (OVLO)
The MAX14527 has a 5.75V (typ) overvoltage threshold
(OVLO).The MAX14528 has a 6.76V (typ) OVLO
threshold.
Thermal-Shutdown Protection
The MAX14527/MAX14528 feature thermal shutdown
circuitry. The internal FET turns off when the junction
temperature exceeds +150°C (typ). The device exits
thermal shutdown after the junction temperature cools
by 20°C (typ).
Applications Information
IN Bypass Capacitor
For most applications, bypass IN to GND with a 1µF
ceramic capacitor as close as possible to the device to
enable ±15kV (HBM) ESD protection on IN. If ±15kV
(HBM) ESD is not required, there is no capacitor
required at IN. If the power source has significant
inductance due to long lead length, take care to pre-
vent overshoots due to the LC tank circuit and provide
protection if necessary to prevent exceeding the +30V
absolute maximum rating on IN.
OUT Output Capacitor
The slow turn-on time provides a soft-start function that
allows the MAX14527/MAX14528 to charge an output
capacitor up to 1000µF.
External OVLO Adjustment Functionality
If OVLO is connected to ground, the internal OVLO
comparator uses the internally set OVLO value.
If an external resistor-divider is connected to OVLO
and V
OVLO
exceeds the OVLO select voltage,
V OVLO_ SELECT , the internal OVLO comparator reads
the IN fraction fixed by the external resistor divider. R 1 =
1MΩ is a good starting value for minimum current con-
sumption. Since V
IN_OVLO , V OVLO_THRESH , and R 1 are
known, R
2
can be calculated from the following formula:
This external resistor-divider is completely independent
from the internal resistor-divider.
ESD Test Conditions
ESD performance depends on a number of conditions.
The MAX14527/MAX14528 are specified for ±15kV
(HBM) typical ESD resistance on IN when IN is
bypassed to ground with a 1µF ceramic capacitor.
HBM ESD Protection
Figure 2a shows the Human Body Model, and Figure
2b shows the current waveform it generates when dis-
charged into a low impedance. This model consists of a
100pF capacitor charged to the ESD voltage of interest,
which is then discharged into the device through a
1.5kΩ resistor.
V V
R
R
IN_OVLO OVLO_THRESH
1
2
= × +
⎡
⎣
⎢
⎤
⎦
⎥ 1
Adjustable Overvoltage Protector
with High Accuracy
6 _______________________________________________________________________________________
CHARGE-CURRENT-
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR Cs
100pF
R
C
1M Ω
R
D
1.5k Ω
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
Figure 2a. Human Body ESD Test Model
I P 100%
90%
36.8%
t RL
TIME
t DL
CURRENT WAVEFORM
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE) I R
10%
0
0
AMPERES
Figure 2b. Human Body Current Waveform