FUNCTIONAL DESCRIPTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
• Operates at a switching frequency equals to FSW2
OVERALL EFFICIENCY ANALYSIS
• Drives integrated low RDS(ON) N-channel power
MOSFETs (NVHV_LC) as its output stage
In battery applications, it is highly recommended to power
every single regulator directly from the battery to obtain full
output capability:
• It offers load disconnect from the input battery when the
output is off (True Cut-Off)
VBAT
VBAT
VBAT
VBAT
VBAT
VBAT
VBAT
VBAT
REG1
REG2
REG3
REG4
REG5
REG6
REG7
REG8
V1 (5.0 V)
• The output is ±4% accuracy
• Output voltage is adjustable by means of an external
resistor divider when in voltage regulation mode
V2 (2.8 / 3.3 V)
V3 (1.2 V / 1.5 V / 1.8 V)
V4 (1.8 V / 2.5 V)
V5 (3.3 V)
• A 240 mV current limit comparator will be used to program/
sense the voltage drop across the current setting resistor
at the bottom of the LED string connected to the REG8
output when the current regulation mode is selected.
This will be used to program the maximum current flowing
and will regulate it
V6 (15 V)
V7 (-7.0 V)
• The output can be adjusted up or down at 2.5% steps for
a total of 10% on each direction allowing Dynamic Voltage
Scaling
V8 (15 V)
Figure 5. Overall Efficiency Analysis
Efficiency analysis includes the following losses:
• MOSFET Conduction Losses
• Maximum output current is adjustable by means of an
external resistor connected to the FB8 pin and then the
output current can be scaled down from the set maximum
in 16 steps through I2C interface
• MOSFET Switching Losses (Except for REG7 due to
external MOSFET and board layout dependence)
• Uses a bootstrap network with an internal diode to power
its synchronous MOSFET
• MOSFET Gate Charging Losses
• MOSFET Deadtime Losses
• All gate drive circuits are supplied from VG.
• Uses integrated compensation
• External Diode Losses (Only for REG7)
• Inductor Winding DC Losses
• The output is monitored for over-current and short-circuit
conditions
• Inductor Core Losses (Assumed to be 20% of DC Losses
as a rule of thumb)
• The regulator is monitored for over-temperature conditions
• The output is monitored for under-voltage and over-
voltage conditions
• Output AC Losses
Efficiency Analysis
Operation Modes
In this configuration, all of the regulators are supplied or
powered directly with 3.6 V nominal, battery voltage.
The switchers will be active when:
• VG is in regulation AND
• There is no GrpD shutdown command through the I2C
interface AND
Efficiency was calculated using the maximum allowed
frequency of 1.5 MHz and 1.0 MHz for F
and F
,
SW1
SW2
respectively, in this configuration. As a result, the following
numbers are valid for worst case operation conditions.
• No faults exist that would cause GrpD to shut down
The following table shows the detailed analysis for each
regulator with V2 at 3.3 V, V3 at 1.2 V, and V4 at 1.8 V.
34704
Analog Integrated Circuit Device Data
Freescale Semiconductor
25
FREESCALE [ Freescale ]
