Datasheet

MCP1790/MCP1791
DS22075B-page 14 © 2010 Microchip Technology Inc.
4.0 DEVICE OVERVIEW
The MCP1790/MCP1791 are high input voltage
regulators capable of providing up to 70 mA of current
at output voltages up to 5.0V. The devices have an
input voltage operating range from 6.0V to 30V, 48V
absolute max. The MCP1790 devices are 3-pin devices
consisting of V
IN
, V
OUT
and GND. The MCP1791
devices have 5 or more pins which add Shutdown and
Power-Good functions to the MCP1790 device.
4.1 Startup
In the start phase, the device must see at least 6.0V to
initiate operation during power up. In the Power-down
mode, the V
IN
monitor will be turned off.
4.2 Thermal Shutdown
The regulator has a thermal shutdown. If the thermal
protection circuit detects an over temperature
condition, typically 157°C junction temperature, the
regulator will shut down. The device will recover from
the thermal shutdown when the junction temperature
drops to 137°C (typical).
4.3 Regulator Output Voltage
The MCP1790/MCP1791 regulators are available in
fixed output voltage configurations. The standard
output voltages are 3.0V, 3.3V, and 5.0V.
4.4 External Protection
4.4.1 TRANSIENT VOLTAGE
PROTECTION (LOAD DUMP)
The regulator is capable of withstanding a 48V
(43.5V ±10) load dump transient for a duration of
500 ms and a repetition rate of 30 seconds
(ES-XW7T-1A278-AC, Ford Motor Company, Test
Pulse G Loaded).
While not necessary, good design practice dictates
adding an external transient suppressor, between VBB
and ground, with a low value resistor in series with the
battery supply and the V
IN
pin, to limit currents and volt-
ages due to electrical transients. Because of the regu-
lator startup current, the resistor value should be less
than (V
BAT
-6V) / 200 mA. For a 12V battery voltage,
the resistor value should be less than 30 ohms.
4.4.2 REVERSE BATTERY PROTECTION
An external reverse battery blocking diode may be
used to provide polarity protection.
FIGURE 4-1: MCP1790/MCP1791 Block Diagram.
-
+
VIN
Monitoring VIN
Temp
Sensor
T1
T2
VOUT
PWRGD
Soft Start
Delay
Reference
Voltage
T2
T1
Monitoring
Temperature
Error Amplifier
Logical Block
Delay
Short Circuit
Protection
VIN
Monitoring VOUT
en
510k
490k
GND
en
SHDN