34704_09 Datasheet, PDF (26/49 Pages) Freescale Semiconductor, Inc – Multiple Channel DC-DC Power Management IC

FUNCTIONAL DESCRIPTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
OVERALL EFFICIENCY ANALYSIS
In battery applications, it is highly recommended to power
every single regulator directly from the battery to obtain full
output capability:
VBAT
REG1
V1 (5.0V)
VBAT
REG2
V2 (2.8 / 3.3V)
VBAT
REG3
V3 (1.2V / 1.5V / 1.8V)
VBAT
REG4
V4 (1.8V / 2.5V)
VBAT
REG5
V5 (3.3V)
VBAT
REG6
V6 (15V)
VBAT
REG7
V7 (-7.0V)
VBAT
REG8
V8 (15V)
Figure 5. Overall Efficiency Analysis
Efficiency analysis includes the following losses:
• MOSFET Conduction Losses
• MOSFET Switching Losses (Except for REG7 due to
external MOSFET and board layout dependence)
• MOSFET Gate Charging Losses
• MOSFET Deadtime Losses
• External Diode Losses (Only for REG7)
• Inductor Winding DC Losses
• Inductor Core Losses (Assumed to be 20% of DC Losses
as a rule of thumb)
• Output AC Losses
Li-Ion Efficiency Analysis
In this configuration, all of the regulators are supplied or
powered directly with 3.6V nominal, battery voltage.
Efficiency was calculated using the maximum allowed
frequency of 1.5MHz and 1.0MHz for F_SW1 and F_SW2,
respectively, in this configuration. As a result, the following
numbers are valid for worst case operation conditions.
The following table shows the detailed analysis for each
regulator with V2 at 3.3V, V3 at 1.2V, and V4 at 1.8V. This is
taken at the specified typical loads on Page15:
Vin (V)
Vout (V)
Iout_typ (A)
Iout_max (A)
DCR(mΩ)
Cout (μF)
ESR (mΩ)
Fsw (kHz)
Lout (μH)
Iin_typ (A)
Iin_max (A)
ILout_peak (A)
ICout_RMS (A)
Pout (W)
Ploss On Chip (W)
Ploss Total (W)
Pin (W)
n (%)
REG1 REG2 REG3 REG4 REG5 REG6 REG7 REG8
3.60
3.60
3.60
3.60
3.60
3.60
3.60
3.60
5.00
3.30
1.20
1.80
3.30
15
-7
15
0.100 0.200 0.150 0.100 0.150 0.050 0.050 0.015
0.500 0.500 0.550 0.300 0.500 0.060 0.060 0.030
230
230
230
310
230
230
230
230
22
22
22
22
22
22
22
22
9.00
9.00
9.00
9.00
9.00
9.00
9.00
9.00
1500 1500 1500 1500 1500 1000 1000 1000
1.50
1.50
1.50
1.50
1.50
4.70
4.70
4.70
0.154 0.201 0.063 0.059 0.150 0.254 0.107 0.077
0.540 0.502 0.209 0.178 0.501 0.304 0.128 0.154
0.724 0.510 0.649 0.444 0.512 0.444 0.443 0.297
0.212 0.005 0.074 0.076 0.0006 0.071 0.129 0.043
0.500 0.660 0.180 0.180 0.495 0.750 0.350 0.225
0.042 0.047 0.038 0.028 0.034 0.135 0.000 0.045
0.044 0.049 0.041 0.030 0.035 0.145 0.027 0.047
0.544 0.709 0.221 0.210 0.530 0.895 0.377 0.272
91.90% 93.12% 81.48% 85.91% 93.33% 60.00% 69.00% 64.00%
34704A overall system efficiency 84%
Overall System
Pout (W)
3.340
Ploss On Chip (W)
0.369
Ploss Total (W)
0.41
Pin (W)
3.75
n (%)
84.00%
34704B overall system efficiency 89%
Overall System
Pout (W)
1.74
Ploss On Chip (W)
0.192
Ploss Total (W)
0.202
Pin (W)
1.942
n (%)
89.6%
34704
26
Analog Integrated Circuit Device Data
Freescale Semiconductor