ADP3208 ON Semiconductor, ADP3208 Datasheet - Page 34

• Manufacturer Part Number: ADP3208
• Description: 7-bit, Programmable, Dual-phase, Mobile, Cpu, Synchronous Buck Controller
• Manufacturer: ON Semiconductor

ADP3208
The compensation values can be calculated as follows:
The standard values for these components are subject to the
tuning procedure described in the Tuning Procedure for
ADP3208 section.
C
di/dt REDUCTION
In continuous inductor-current mode, the source current of the
high-side MOSFET is approximately a square wave with a duty
ratio equal to n × V
the maximum output current. To prevent large voltage
transients, use a low ESR input capacitor sized for the
maximum rms current. The maximum rms capacitor current
occurs at the lowest input voltage and is given by
where I
In a typical notebook system, the battery rail decoupling is
achieved by using MLC capacitors or a mixture of MLC
capacitors and bulk capacitors. In this example, the input
capacitor bank is formed by eight pieces of 10 μF, 25 V MLC
capacitors, with a ripple current rating of about 1.5 A each.
SOFT TRANSIENT SETTING
As described in the Theory of Operation section, during the
soft transient, the slew rate of the V
change is controlled by the ST pin capacitance. Because the
timing of exiting deeper sleep is critical, the ST pin capacitance
is set to satisfy the slew rate for a fast exit of deeper sleep as
follows:
where:
7.5 μA is the source/sink current of the ST pin.
IN
SELECTION AND INPUT CURRENT
C
C =
C
C
R =
I
I
CRMS
CRMS
FB
ST
A
A
B
O
=
is the output current.
=
=
n
C
T
T
R
=
=
T
R
SLEWRATE
×
C
R
A
B
B
D
D
. 0
A
R
E
18
×
O
×
7
I
×
R
5 .
×
O
T
OUT
B
40
×
μA
A
/V
A
n
C4E
IN
×
×
1
and an amplitude that is one-n
D
2
×
−
1
1
0.18
CORE
−
1
reference voltage
=
9
6 .
A
Rev. 1 | Page 34 of 38 | www.onsemi.com
th
of
(37)
(38)
(39)
(40)
(41)
(42)
SLEWRATE
and is defined as 10 mV/μA in the IMVP-6+ specification.
C
SELECTING THERMAL MONITOR COMPONENTS
To monitor the temperature of a single-point hot spot, set
R
temperature. For example, if the alarm temperature for VRTT is
100°C and a Vishey thermistor (NTHS-0603N011003J) with a
resistance of 100 kΩ at 25°C, or 6.8 kΩ at 100°C, is used, the
user can set R
To monitor the temperature of multiple-point hot spots, use the
configuration shown in Figure 44. If any of the monitored hot
spots reaches the alarm temperature, the VRTT signal is
asserted. The following calculation sets the alarm temperature:
where V
Because the forward current is very small, the forward drop
voltage is very low, that is, less than 100 mV. Assuming the same
conditions used for the single-point thermal monitoring
example—that is, an alarm temperature of 100°C and use of an
NTHS-0603N011003J Vishay thermistor—solving Equation 42
gives a R
7.32 kΩ (1%).
ST
TTSET1
ADP3208
is 750 pF, and the closest standard capacitance is 680 pF.
R
TTSET1
equal to the NTC thermistor’s resistance at the alarm
FD
TTSET
ADP3208
is the forward drop voltage of the parallel diode.
C4E
=
Figure 44. Multiple-Point Thermal Monitoring
of 7.37 kΩ, and the closest standard resistor is
TTSET1
Figure 43. Single-Point Thermal Monitoring
1
1
is the voltage slew rate for exiting deeper sleep
R
R
2 /
2 /
TTSNS
VRTT
+
−
equal to 6.8 kΩ (the R
VCC
V
V
V
V
REF
REF
FD
FD
12
11
37
R
R
×
5V
TTSNS
R
1MΩ
VRTT
C
TH1AlarmTe
VCC
TT
11
37
12
R
mperature
R
TTSET1
TH1
5V
TH1
R
C
TTSET1
TT
at 100°C).
R
R
TTSET2
TH2
R
TH1
R
R
TTSETn
THn
(43)