MAX1908 datasheet(22/27 Pages) MAXIM

22 / 27 page

The crossover frequency is given by:

The CCI loop dominant compensation pole:

where the GMI amplifier output impedance, ROGMI =

10M

Ω.

To calculate the CCI loop compensation pole, CCI:

GMI = 1µA/mV

GMOUT = 3.33A/V

ROGMI = 10M

Ω

f = 400kHz

Choose crossover frequency fCO_CI to be 1/5th the

MAX1908/MAX8724 switching frequency:

Solving for CCI, CCI = 2nF.

To be conservative, set CCI = 10nF, which sets the

crossover frequency at:

The compensation pole, fP_CI is set at:

CCS Loop Definitions

Compensation of the CCS loop depends on the parame-

ters and components shown in Figure 9. CCS is the CCS

loop compensation capacitor. ACSS is the internal gain of

the current-sense amplifier. RS1 is the input current-

sense resistor, RS1 = 10m

Ω. ROGMS is the equivalent

output impedance of the GMS amplifier

≥ 10MΩ. GMS is

GMI

PCI

OGMI

0 0016

GMI

kHz

CO CI

210

GMI

kHz

CO CI

PCI

OGMI

GMI

CO CI

Low-Cost Multichemistry Battery Chargers

______________________________________________________________________________________

GMOUT

CCI

GMI

ICTL

CCI

ROGMI

CSIP

CSIN

CSI

RS2

Figure 7. CCI Loop Diagram

CCI LOOP GAIN

vs. FREQUENCY

FREQUENCY (Hz)

100k

10k

110

100

-40

-20

100

-60

0.1

CCI LOOP PHASE

vs. FREQUENCY

FREQUENCY (Hz)

100k

10k

100

-90

-75

-60

-45

-30

-15

-105

0.1

Figure 8. CCI Loop Gain/Phase vs. Frequency

MAX1908 Datenblatt(PDF) 22 Page - Maxim Integrated Products

MAX1908 Datenblatt(HTML) 22 Page - Maxim Integrated Products

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

Datenblatt Download

Link URL