CDH2D09 View Datasheet(PDF) - Maxim Integrated
Part Name
Description
MFG CO.
'CDH2D09' PDF : 44 Pages View PDF
PMIC with Integrated Charger and
Smart Power Selector for Handheld Devices
Step-Down Inductor
Choose the step-down regulator inductance to be
4.7µH. The minimum recommended saturation current
requirement is 600mA. In PWM mode, the peak induc-
tor currents are equal to the load current plus one half
of the inductor ripple current. The MAX8671X works
well with physically small inductors. See Table 6 for
suggested inductors.
The peak-to-peak inductor ripple current during PWM
operation is calculated as follows:
IP−P
=
VOUT(VSYS − VOUT)
VSYS × fS × L
where fS is the 2MHz switching frequency.
The peak inductor current during PWM operation is cal-
culated as follows:
IL
_ PEAK
=
ILOAD
+
IP−P
2
Step-Down Converter Output Current
The three MAX8671X step-down regulators each pro-
vide at least 425mA of output current when using a rec-
ommended inductor (Table 6). To calculate the
maximum output current for a particular application and
inductor use the following two-step process (as shown
in Figure 10):
1) Use the following equation to calculate the approxi-
mate duty cycle (D):
D = VOUT + IOUTTAR(RN + RL)
VIN + IOUTTAR(RN − RP)
where:
VOUT = output voltage
IOUTTAR = target (desired) output current—cannot
be more than the minimum p-channel current-limit
threshold
RN = n-channel on-resistance
RP = p-channel on-resistance
RL = external inductor’s ESR
VIN = input voltage—MAXIMUM
2) Use the following equation to calculate the maximum
output current (IOUTMAX):
IOUTMAX
=
ILIM −
1+ (RN
VOUT(1− D)
2×f×L
+
RL
)
1−
2×f
D
×L
where:
ILIM = p-channel current-limit threshold—MINIMUM
VOUT = output voltage
D = approximate duty cycle derived from step 1
f = oscillator frequency—MINIMUM
L = external inductor’s inductance—MINIMUM
RN = n-channel on-resistance
RL = external inductor’s ESR
Table 6. Suggested Inductors
MANUFACTURER
Sumida
Taiyo Yuden
TDK
TOKO
SERIES
CDRH2D11HP
CDH2D09
NR3012
NR3010
VLF3012
VLF3010
DE2812C
DE2810C
INDUCTANCE
(µH)
4.7
4.7
4.7
4.7
4.7
4.7
4.7
4.7
ESR (Ω)
190
218
130
190
160
240
130
180
CURRENT RATING
(mA)
750
700
770
750
740
700
880
640
DIMENSIONS (mm)
3.0 x 3.0 x 1.2 = 10.8mm3
3.0 x 3.0 x 1.0 = 9.0mm3
3.0 x 3.0 x 1.2 = 10.8mm3
3.0 x 3.0 x 1.0 = 9.0mm3
2.8 x 2.6 x 1.2 = 8.7mm3
2.8 x 2.6 x 1.0 = 7.3mm3
3.0 x 2.8 x 1.2 = 10.8mm3
3.0 x 2.8 x 1.0 = 8.4mm3
34 ______________________________________________________________________________________
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