PM6641 Datasheet, PDF (32/47 Pages) STMicroelectronics – Monolithic VR for chipset and DDR2/3 supply for ultra-mobile PC (UMPC) applications

Device description
PM6641
where VREF = 0.9V is the constant voltage forced by CSNS pin, R_CSNS [Ω] is the resistor
connected between CSNS and AGND, α is the coefficient that collects the MOS current
sensing scaling factor and other design parameters and I_CL is the peak current limit [A].
The following table resumes values for all the switching regulators.
Table 11. Typical SW regulators values
SW regulator
1.8V
1.5V
1.05V
α
333x10e3
222x10e3
278x10e3
The following graph is a plot of the switching regulators peak current limit, increasing the
R_CSNS resistor:
Figure 33. SW regulators peak current limit
7.00
6.00
CL_1V8
5.00
CL_1V5
CL_1V05
4.00
3.00
2.00
1.00
0.00
40
60
80
100
120
140
160
180
Rcsns [kOhm]
From the previous plot and table it’s clear that the three regulators peak current limits are
scaled; by changing the R_CSNS external resistor the three peak current limits all change.
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