Rainbow Electronics MAX4987BE - Manual (Page 7)

Overvoltage Lockout (OVLO)
The MAX4987AE/MAX4987BE have a 6.15V (typ) over-
voltage threshold (OVLO). When V
IN is greater than
V
OVLO
, ACOK is high impedance.
ACOK
ACOK is an active-low open-drain output that asserts
low when V
UVLO < V IN < V OVLO following the 30ms
(typ) debounce period. Connect a pullup resistor from
ACOK to the logic I/O voltage of the host system.
During a short-circuit fault,
ACOK may deassert due to
V IN not being in the valid operating voltage range.
Thermal-Shutdown Protection
The MAX4987AE/MAX4987BE feature thermal-shutdown
circuitry. The internal nFET switch turns off when the
junction temperature exceeds T
SHDN
and immediately
goes into a fault mode. The device exits thermal shut-
down after the junction temperature cools by +40°C (typ).
Applications Information
IN Bypass Capacitor
For most applications, bypass IN to GND with a 1µF
ceramic capacitor as close to the device as possible to
enable ±15kV HBM ESD protection on IN. If ±15kV HBM
ESD protection is not required, there is no capacitor
required at IN. If the power source has significant induc-
tance due to long lead length, take care to prevent over-
shoots due to the LC tank circuit and provide protection if
necessary to prevent exceeding the absolute maximum
rating on IN.
ESD Test Conditions
ESD performance depends on a number of conditions.
The MAX4987AE/MAX4987BE are specified for ±15kV
HBM ESD protection on the CD+, CD-, and IN pins
when IN is bypassed to ground with a 1µF ceramic
capacitor. The CD+ and CD- inputs are also protected
against ±15kV Air Gap and ±6kV contact IEC 61000-4-
2 ESD events.
Human Body Model
Figure 3 shows the Human Body Model, and Figure 4
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 inter-
est, that is then discharged into the device through a
1.5kΩ resistor.
IEC 61000-4-2
The IEC 61000-4-2 standard covers ESD testing and per-
formance of finished equipment. It does not specifically
refer to integrated circuits. The MAX4987AE/ MAX4987BE
MAX4987AE/MAX4987BE
Overvoltage-Protection Controller
with USB ESD Protection
_______________________________________________________________________________________ 7
nFET SWITCH
ON nFET SWITCH
ON
SWITCH OFF
CURRENT
THROUGH
nFET SWITCH
I LIM
t OFF
t RETRY
Figure 2. Autoretry Timing Diagram
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 3. 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) Ir
10%
0
0
AMPERES
Figure 4. Human Body Current Waveform