RHFL4913XX25_10 Datasheet, PDF (8/19 Pages) STMicroelectronics – Rad-hard positive fixed voltage regulator

Device description
5
Device description
RHFL4913XX25, RHFL4913XX33, RHFL4913XX50
The RHFL4913 fixed voltage contains a PNP type power element controlled by a signal
resulting from amplified comparison between the internal temperature compensated band-
gap cell and the fraction of the desired output voltage value. This fractional value is obtained
from an internal-to-die resistor divider bridge set by STMicroelectronics. The device is
protected by several functional blocks.
5.1
Low pin count package limitations
Some functions (INHIBIT, OCM, SENSE) are not available due to lack of pins.
Corresponding die pads are by default connected inside silicon.
5.2
SENSE pin
The load voltage is applied by a Kelvin line connected to SENSE pin: Voltage feed-back
comes from the internal divider resistor bridge. Therefore possible output voltages are set
by manufacturer mask metal options. SENSE pin is not available in 3pin packages.
5.3
Inhibit ON-OFF control
By setting INHIBIT pin TTL-high, the device switches off the output current and voltage. The
device is ON when INHIBIT pin is set low. Since INHIBIT pin is internally pulled down, it can
be left floating in case inhibit function is not utilized. INHIBIT pin is not available in 3pin
packages.
5.4
Overtemperature protection
A temperature detector internally monitors the power element junction temperature. The
device goes OFF at approx. 175 °C, returning to ON mode when back to approx. 40 °C. It is
worth noting that when the internal temperature detector reaches 175 °C, the active power
element can be at 225 °C: device reliability cannot be granted in case of extensive operation
under these conditions.
5.5
Overcurrent protection
I_SC pin. An internal non-fold back short-circuit limitation is set with I_SHORT > 3.8 A (V_O is 0
V). This value can be reduced by an external resistor connected between I_SC pin and V_I pin,
with a typical value range of 25 kΩ to 200 kΩ. This adjustment feature is not available in 3
pin packages. To keep excellent V_O regulation, it is necessary to set I_SHORT 1.6 times
greater than the maximum desired application I_O. When I_O reaches I_SHORT – 300 mA, the
current limiter overrules regulation and V_O starts to drop and the OCM flag is risen. When no
current limitation adjustment is required, I_SC pin must be left unbiased (as it is in 3 pin
packages).
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Doc ID 10004 Rev 11