PM6670ASTR STMicroelectronics, PM6670ASTR Datasheet - Page 46

• Manufacturer Part Number: PM6670ASTR
• Description: IC CTLR DDR2/3 MEM PS 24VFQFPN
• Manufacturer: STMicroelectronics

Specifications of PM6670ASTR

• Applications: Memory, DDR2/DDR3 Regulator
• Current - Supply: 800µA
• Voltage - Supply: 4.5 V ~ 36 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-VFQFN, 24-VFQFPN
• For Use With: 497-8412 - BOARD EVAL PM6670AS DDR2/3497-8411 - BOARD EVAL PM6670S DDR2/3
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-6305-2; PM6670ATR

Application information
8.1.6
46/53
VDDQ current limit setting
The valley current limit is set by R
current. The valley of the inductor current I
Equation 45
The output current limit depends on the current ripple as shown I
Figure 39. Valley current limit waveforms
As the valley threshold is fixed, the greater the current ripple, the greater the DC output
current will be. If an output current limit greater than I
range is required, the minimum current ripple must be considered in the previous formula.
Then the resistor R
Equation 46
where R
temperature effect and the worst case value in R
The accuracy of the valley current also depends on the offset of the internal comparator
(±5 mV).
The negative valley-current limit (if the device works in forced-PWM mode) is given by:
Equation 47
DSon
is the drain-source on-resistance of the low-side switch. Consider the
MAX LOAD 1
Current
Valley current limit
CSNS
Inductor current
is:
Doc ID 14436 Rev 2
I
CSNS
Lvalley
R
CSNS
I
NEG
and must be chosen to support the maximum load
=
Inductor current
I
=
LOAD
Lvalley
MAX LOAD 2
=
R
DSon
120
R
(max)
100
DSon
DSon
is:
mV
⋅
uA
I
Lvalley
−
LOAD
calculation (typically +0.4%/°C).
Δ
2
I
L
(max) over all the input voltage
Figure 39
Time
:
PM6670AS