STEVAL-ISA051V2 STMicroelectronics, STEVAL-ISA051V2 Datasheet - Page 20
![BOARD EVAL PM6670AS DDR2/3](/photos/9/13/91339/steval-isa051v2_sml.jpg)
STEVAL-ISA051V2
Manufacturer Part Number
STEVAL-ISA051V2
Description
BOARD EVAL PM6670AS DDR2/3
Manufacturer
STMicroelectronics
Type
DC/DC Switching Converters, Regulators & Controllersr
Specifications of STEVAL-ISA051V2
Design Resources
STEVAL-ISA051V2 Gerber Files STEVAL-ISA051V2 Schematic STEVAL-ISA051V2 Bill of Material
Main Purpose
Special Purpose DC/DC, DDR Memory Supply
Outputs And Type
4, Non-Isolated
Voltage - Output
1.5V, 1.8V
Voltage - Input
4.5 ~ 36V
Regulator Topology
Buck
Board Type
Fully Populated
Utilized Ic / Part
PM6670A
Input Voltage
4.5 V to 36 V
Output Voltage
1.8 V, 1.5 V
Product
Power Management Modules
Silicon Manufacturer
ST Micro
Silicon Core Number
PM6670AS
Kit Application Type
Power Management
Application Sub Type
DDR2/3 Memory Power Supply Controller
Kit Contents
Board
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Current - Output
-
Power - Output
-
Frequency - Switching
-
Lead Free Status / Rohs Status
Lead free / RoHS Compliant
For Use With/related Products
PM6670AS
Other names
497-8412
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
STEVAL-ISA051V2
Manufacturer:
STMicroelectronics
Quantity:
1
Device description
7.1
20/53
VDDQ section - constant on-time PWM controller
The PM6670AS uses a pseudo-fixed frequency, constant on-time (COT) controller as the
core of the switching section. It is well known that the COT controller uses a relatively simple
algorithm and uses the ripple voltage derived across the output capacitor’s ESR to trigger
the on-time one-shot generator. In this way, the output capacitor’s ESR acts as a current
sense resistor providing the appropriate ramp signal to the PWM comparator. Nearly
constant switching frequency is achieved by the system’s loop in steady-state operating
conditions by varying the on-time duration, avoiding thus the need for a clock generator. The
on-time one shot duration is directly proportional to the output voltage, sensed at VSNS pin,
and inversely proportional to the input voltage, sensed at the VOSC pin, as follows:
Equation 1
where K
(40 ns typ.). The one-shot generator directly drives the high-side MOSFET at the beginning
of each switching cycle allowing the inductor current to increase; after the on-time has
expired, an off-time phase, in which the low-side MOSFET is turned on, follows. The off-time
duration is solely determined by the output voltage: when lower than the set value (i.e. the
voltage at VSNS pin is lower than the internal reference V
rectifier is turned off and a new cycle begins
Figure 26. Inductor current and output voltage in steady state conditions
OSC
is a constant value (130ns typ.) and τ is the internal propagation delay
Inductor
Inductor
current
current
Output
Output
voltage
voltage
V
V
reg
reg
Ton
Ton
Doc ID 14436 Rev 2
T
ON
=
Toff
Toff
K
OSC
(Figure
V
V
OSC
SNS
+
26).
τ
R
= 0.9 V), the synchronous
t
t
PM6670AS