pt5109 China Resources Powtech (Shanghai) Co., Ltd, pt5109 Datasheet - Page 8

• Manufacturer Part Number: pt5109
• Description: High-psrr 300ma Ldo
• Manufacturer: China Resources Powtech (Shanghai) Co., Ltd

Figure 3. Graph showing a typical variation in
capacitance vs. DC bias
The ceramic capacitor’s capacitance can vary with
temperature. The capacitor type X7R, which operates
over a temperature range of -55˚C to +125˚C, will only
vary the capacitance to within ±15%. The capacitor
type X5R has a similar tolerance over a reduced
temperature range of -55˚C to +85˚C. Most large value
ceramic capacitors ( 2.2µF) are manufactured with Z5U
or Y5V temperature characteristics. Their capacitance
can drop by more than 50% as the temperature goes
from 25˚C to 85˚C. Therefore X7R is recommended
over Z5U and Y5V in applications where the ambient
temperature will change significantly above or below
25˚C.
China Resources Powtech (Shanghai) Limited
PT5109_DS Rev EN_2.0
WWW.CRPOWTECH.COM
Tantalum capacitors are less desirable than ceramic for
use as output capacitors because they are more
expensive when comparing equivalent capacitance and
voltage ratings in the 1µF to 4.7µF range.
Another important consideration is that tantalum
capacitors have higher ESR values than equivalent size
ceramics. This means that while it may be possible to
find a tantalum capacitor with an ESR value within the
stable range, it would have to be larger in capacitance
(which means bigger and more costly) than a ceramic
capacitor with the same ESR value. It should also be
noted that the ESR of a typical tantalum will increase
about 2:1 as the temperature goes from 25˚C down to
−40˚C, so some guard band must be allowed.
NO-LOAD STABILITY
The PT5109 will remain stable and in regulation with
no external load. This is especially important in CMOS
RAM keep-alive applications.
ON/OFF INPUT OPERATION
The PT5109 is turned off by pulling the VEN pin low,
and turned on by pulling it high. If this function is not
used, the VEN pin should be tied to VIN to keep the
regulator output on at all time. To assure proper
operation, the signal source used to drive the VEN
input must be able to swing above and below the
specified turn-on/off voltage thresholds listed in the
Electrical Characteristics section under VIL and VIH.
High-PSRR 300mA LDO
PT5109
Page 8