STEVAL-ISA052V2 STMicroelectronics, STEVAL-ISA052V2 Datasheet - Page 35

• Manufacturer Part Number: STEVAL-ISA052V2
• Description: BOARD EVAL BASED ON PM6675A
• Manufacturer: STMicroelectronics
• Type: DC/DC Switching Converters, Regulators & Controllersr

Specifications of STEVAL-ISA052V2

• Design Resources: STEVAL-ISA052V2 Gerber Files STEVAL-ISA052V2 Schematic STEVAL-ISA052V2 Bill of Material
• Main Purpose: DC/DC, Step Down with LDO
• Outputs And Type: 2, Non-Isolated
• Voltage - Output: 1.5V, 0.6 ~ 3.3V
• Voltage - Input: 4.5 ~ 36 V
• Regulator Topology: Buck
• Board Type: Fully Populated
• Utilized Ic / Part: PM6675AS
• Input Voltage: 4.5 V to 36 V
• Output Voltage: 1.5 V
• Product: Power Management Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Power - Output: -
• Frequency - Switching: -
• Lead Free Status / Rohs Status: Supplier Unconfirmed
• For Use With/related Products: PM6675AS
• Other names: 497-8413

PM6675AS
8.1.1
Equation 28 a
Equation 28 b
Referring to the typical application schematic (figs. 1 and 23), the final expression is then:
Equation 29
Even if the switching frequency is theoretically independent from battery and output
voltages, parasitic parameters involved in power path (like MOSFETs on-resistance and
inductor DCR) introduce voltage drops responsible of a slight dependence on load current.
In addition, the internal delay is cause of a light dependence from input voltage.
Table 10.
Inductor selection
Once the switching frequency has been defined, the inductance value depends on the
desired inductor ripple current. Low inductance value means great ripple current that brings
to poor efficiency and great output noise. On the other hand a great current ripple is
desirable for fast transient response when a load step is applied.
Otherwise, great inductance brings to good efficiency but the transient response is critical,
especially if V
assure system stability and jitter-free operations (see Output capacitor selection paragraph).
The product of the output capacitor ESR multiplied by the inductor ripple current must be
taken into consideration. A good trade-off between the transient response time, the
efficiency, the cost and the size is to choose the inductance value in order to maintain the
inductor ripple current between 20 % and 50 % (usually 40 %) of the maximum output
current.
The maximum inductor ripple current, ∆I
R1 (kΩ)
330
330
330
330
330
330
Typical values for switching frequency selection
INmin
- V
out
is little. Moreover a minimum output ripple voltage is necessary to
f
SW
=
R2 (kΩ)
K
α
11
13
15
18
20
22
α
α
OSC
OSC
LMAX
OSC
OUT
=
=
=
, occurs at the maximum input voltage.
R
V
1
V
V
R
V
OUT
+
OSC
SNS
IN
2
R
2
⋅
K
Approx switching frequency (kHz)
OSC
1
Application information
250
300
350
400
450
500
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