Rainbow Electronics MAX6871 - Manual (Page 10)

MAX6870/MAX6871
Detailed Description
The MAX6870/MAX6871 EEPROM-configurable, multi-
voltage supply sequencers/supervisors monitor several
voltage-detector inputs, two auxiliary inputs and four
general-purpose logic inputs, and feature programma-
ble outputs for highly-configurable, power-supply
sequencing applications. The MAX6870 features six
voltage-detector inputs and eight programmable out-
puts, while the MAX6871 features four voltage-detector
inputs and five programmable outputs. Manual reset
and margin disable inputs simplify board-level testing
during the manufacturing process. The MAX6870/
MAX6871 feature an accurate internal 1.25V reference.
For greater accuracy, connect an external +1.25V ref-
erence to REFIN.
All voltage detectors provide two configurable thresh-
olds for undervoltage/overvoltage or dual undervoltage
detection. One high-voltage input (IN1) provides detec-
tor threshold voltages from +1.25V to +7.625V in 25mV
increments or +2.5V to +13.2V in 50mV increments.
A bipolar input (IN2) provides detector threshold volt-
ages from ±1.25V to ±7.625V in 25mV increments, or
±2.5V to ±15.25V in 50mV increments. Positive inputs
(IN3–IN6) provide detector threshold voltages from
+0.5V to +3.05V in 10mV increments, or +1.0V to +5.5V
in 20mV increments.
An internal 10-bit ADC monitors the voltage-detector
inputs and two auxiliary inputs through a multiplexer
that automatically sequences through all inputs every
200ms. The host controller communicates with the
MAX6870/MAX6871s’ internal 4kb user EEPROM,
configuration EEPROM, configuration registers, ADC
registers, and fault registers through an SMBus/I
2 C-
compatible serial interface (see Figure 1).
Programmable output options include active-high,
active-low, open-drain, weak pullup, push-pull, and
charge pump. Select the charge-pump output feature
to drive n-channel FETs for power-supply sequencing
(see the Applications Information section). The outputs
swing between 0 and (V
ABP + 5V) when configured for
charge-pump operation.
Program each output to assert on any voltage-detector
input, general-purpose logic input, watchdog timer,
manual reset, or other output stages. Programmable
timing-delay blocks configure each output to wait
between 25µs and 1600ms before deasserting. A fault
register logs the conditions that caused each output to
assert (undervoltage, overvoltage, manual reset, etc.).
The MAX6870/MAX6871 feature two watchdog timers,
adding flexibility. Program each watchdog timer to assert
one or more programmable outputs. Program each
EEPROM-Programmable Hex/Quad
Power-Supply Sequencers/Supervisors with ADC
10 ______________________________________________________________________________________
Pin Description (continued)
PIN
MAX6870 MAX6871
NAME FUNCTION
30 30 IN1
High Voltage Input 1. Configure IN1 to detect voltage thresholds from +2.5V to +13.2V in 50mV
increments or +1.25V to +7.625V in 25mV increments. For improved noise immunity, bypass
IN1 to GND with a 0.1µF capacitor installed as close to the device as possible.
31 31 REFIN
Reference Voltage Input. Configure the MAX6870/MAX6871 to use either an internal reference
or external reference (see Table 9). When configured for an internal reference, leave REFIN
unconnected. When configured for an external reference, connect a +1.225V to +1.275V
reference to REFIN.
32 2 PO1
Programmable Output 1. Configurable active-high, active-low, open-drain, weak pullup, or
charge-pump output. PO1 pulls low with a weak 10µA internal current sink for +1V < V
ABP
< V
UVLO
. PO1 assumes its programmed conditional output state when ABP exceeds UVLO.
— — EP Exposed Paddle. Exposed paddle is internally connected to GND.