MAX16052 Datasheet, PDF (9/12 Pages) Maxim Integrated Products – High-Voltage, Adjustable Sequencing/Supervisory Circuits

High-Voltage, Adjustable
Sequencing/Supervisory Circuits
Monitor Input (IN)
Connect the center point of a resistive divider to IN to
monitor external voltages (see R1 and R2 of Figure 4). IN
has a rising threshold of V_TH = 0.5V and a falling thresh-
old of 0.495V (5mV hysteresis). When V_IN rises above
V_TH and EN is high, OUT goes high after the adjustable
t_DELAY period. When V_IN falls below 0.495V, OUT goes
low after a 18µs delay. IN has a maximum input current
of 60nA, so large value resistors are permitted without
adding significant error to the resistive divider.
Adjustable Delay (CDELAY)
When V_IN rises above V_TH with EN high, the internal
250nA current source begins charging an external
capacitor connected from CDELAY to GND. When the
voltage at CDELAY reaches 1V, the output asserts
(OUT goes high). When the output asserts, C_CDELAY is
immediately discharged. Adjust the delay (t_DELAY) from
when V_IN rises above V_TH (with EN high) to OUT going
high according to the equation:
t_DELAY = C_CDELAY × (4 × 10⁶Ω) + (30μs)
where t_DELAY is in seconds and C_CDELAY is in Farads.
Enable Input (EN)
The MAX16052/MAX16053 offer an active-high enable
input (EN). With V_IN above V_TH, drive EN high to force
OUT high after the capacitor-adjustable delay time. The
EN-to-OUT delay time (t_PROP) can be calculated from
when EN goes above the EN threshold using the equation:
t_PROP = C_CDELAY × (4 × 10⁶Ω) + (14μs)
where t_PROP is in seconds and C_CDELAY is in Farads.
Drive EN low to force OUT low within 300ns for the
MAX16052 and within 400ns for the MAX16053.
Output (OUT)
The MAX16052 offers an active-high, open-drain output
while the MAX16053 offers an active-high push-pull out-
put. The push-pull output is referenced to V_CC. The
open-drain output requires a pullup resistor and can be
pulled up to 28V.
Applications Information
Input Threshold
The MAX16052/MAX16053 monitor the voltage on IN
with an external resistive divider (Figure 4). R1 and R2
can have very high values to minimize current con-
sumption due to low IN leakage currents (60nA max).
Set R2 to some conveniently high value (200kΩ for ±1%
additional variation in threshold, for example) and cal-
culate R1 based on the desired monitored voltage
using the following formula:
R1 =
R2 ×
⎡
⎢
⎣
V_MONITOR
V_TH
⎤
− 1_⎥
⎦
where V_MONITOR is the desired monitored voltage and
V_TH is the reset input threshold (0.5V).
Pullup Resistor Values (MAX16052 Only)
The exact value of the pullup resistor for the open-drain
output is not critical, but some consideration should be
made to ensure the proper logic levels when the device
is sinking current. For example, if V_CC = 2.25V and the
pullup voltage is 28V, keep the sink current less than
0.5mA as shown in the Electrical Characteristics table.
As a result, the pullup resistor should be greater than
56kΩ. For a 12V pullup, the resistor should be larger
than 24kΩ. Note that the ability to sink current is depen-
dent on the V_CC supply voltage.
Ensuring a Valid OUT
Down to V_CC = 0V (Push-Pull OUT)
In applications in which OUT must be valid down to
V_CC = 0V, add a pulldown resistor between OUT and
GND for the push-pull output (MAX16053). The resistor
sinks any stray leakage currents, holding OUT low
(Figure 3). The value of the pulldown resistor is not criti-
cal; 100kΩ is large enough not to load OUT and small
enough to pull OUT to ground. The external pulldown
cannot be used with the open-drain OUT output.
V_CC
V_CC
OUT
MAX16053
100kΩ
GND
Figure 3. Ensuring OUT Valid to V_CC = 0V
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