MP201 – DYING GASP STORAGE AND RELEASE CONTROL IC

MP201 Rev. 1.01

www.MonolithicPower.com

9

11/27/2012

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© 2012 MPS. All Rights Reserved.

APPLICATION INFORMATION

SET STORAGE VOLTAGE

The storage voltage can be set by choosing

appropriate external feedback resistors R1 and

R2 which is shown in Figure 4.

R1

R2

Cstorage

STRG

FB1

Figure 4 – Feedback Circuit for Storage

Voltage

The storage voltage is determined by:

STORAGE

FB1

R1

V(1

) V

R2

=+

×

Here is the example, if the storage voltage is

set to be 20V, choose R2 to be 40kΩ, R1 will be

then given by:

FB2

FB2

40k

(20 V

)

R1

760k

V

Ω×

−

==

Ω

Table 1 lists the recommended resistors for

different storage voltages.

Table 1 – Resistor Selection for Different

Storage Voltages

R1 (kΩ)

R2 (kΩ)

15

750

53.2

19

750

41.6

23

845

37.4

Select Release Voltage and Input Capacitors

The release voltage can be set by choosing

external feedback resistors R3 and R4 which is

shown in Figure 5.

R3

R4

VIN

FB2

Cin

Cf

Figure 5 – Release Feedback Circuit

Similarly, the release voltage is set by:

RELEASE

FB2

R3

V(1

) V

R4

=+

×

However, the selection of R3 and R4 not only

determines the release voltage, but impacts the

stability.

Generally,

choosing

R3

to

be

300~500kΩ is recommended for a stable

recommended resistors setup for different

release voltages.

Table 2 – Resistor Selection for Different

Release Voltages

(V)

R3

(kΩ)

R4

(kΩ)

Cf

(pF)

11

475

47.5

15

47

10.2

464

49.9

15

47

9.0

324

40.2

15

47

Select Storage Capacitor

The Storage Capacitor is for energy storage

during normal operation and the energy will be

released to VIN in case of losing input power.

Typically,

a

general

purpose

electrolytic

capacitor is recommended.

The voltage rating of storage capacitor needs to

be higher than the targeted storage voltage.

The voltage rating of storage capacitor can be

fully utilized since the voltage on storage

capacitor is very stable during normal operation.

There will be less ripple current/voltage for most

of the time during normal operation. The ripple

current rating of storage cap can be less

consideration.

The needed capacitance is dependent on how

long the dying gasp time based on typically