PRM48JH480T250A00 Datasheet, PDF (30/44 Pages) Vicor Corporation – High Efficiency Converter

PRM48JH480x250A00
Design Guidelines (Adaptive Loop Operation)
In Adaptive Loop Operation, the internal voltage control circuitry is
enabled and the voltage at the output terminals is regulated. The
part is nominally set to provide a fixed 48.0 V output, and the TRIM
pin can be used to adjust the output over the range of 20.0 V
to 55.0 V.
When used with a VTM, the AL pin provides ability to program an
Adaptive Loop load line to compensate for the output resistance
(R_OUT) of a downstream VTM, while the VT pin provides temperature
compensation to account for changes in the VTM R_OUT over
temperature.
Trim Mode and Output Trim Control (Adaptive Loop Operation)
In Adaptive Loop Operation, during any start up and after ENABLE
transitions high, the TRIM pin voltage is sampled to determine if
trim is active or inactive. If the sampled TRIM voltage is higher than
3.20 V then the PRM will disable trim. In this case, for all subsequent
operation the output voltage will be programmed to the nominal
output of 48.0 V and the TRIM pin will be ignored during normal
operation.
If the sampled TRIM voltage is between 1.00 V and 2.75 V then the
PRM will activate trim mode and it will remain in this mode as long
as the PRM is operating.
This selection persists until the PRM is restarted with the ENABLE
pin, or due to fault auto-recovery.
V_CCINT
The TRIM pin is pulled up internally to V_{CC_INT} thorough a 10 kΩ
resistor. V_TRIM can be actively set with a DAC that is ground
referenced to SGND. V_TRIM can be passively set by connecting a
resistor, R_TRIM, from TRIM to SGND such that the voltage divider
made with V_{CC_INT} and the 10 kΩ pull up yields the desired V_TRIM.
The formula for calculating this resistor is provided in Equation (1a).
V_OUT = V_TRIM • 20
R _TRIM
=
10 kŸuV_TRIM
V_CCINT <V_TRIM
=
10 kŸuV_{OUT_SET}
20 uV_CCINT <V_{OUT_SET}
(1)
(1a)
For 1.00 V≤ V_TRIM ≤ 2.75 V where V_{OUT_SET} is the desired output
voltage.
The output voltage tranfer function saturates for applied TRIM
voltages above approximately 2.75 V as illustrated in Figure 26 to
prevent the output from being driven above its rated output voltage.
When TRIM is set lower than 1.00 V the output voltage is not
specified and stable operation is not guaranteed.
PRM V_OUT vs. V_TRIM
60
60
Recommended Range
50
50
40
40
30
30
V_TRIM
10 KΩ
TRIM
R_TRIM
SGND
SGND
Micro
Controller
SGND
Figure 25 — TRIM Connection
The output as a function of V_TRIM is defined by equation (1) for
1.00 V ≤ V_TRIM ≤ 2.75 V, and allows for an output voltage ranging from
20.0 V to 55.0 V.
20
20
10
10
Unspecified
OperaƟon
0
0
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25
TRIM Pin Voltage (V)
Output Voltage (V)
TRIM Pin Resistor (KΩ)
Figure 26 — PRM V_OUT vs. V_TRIM
When trim is enabled the voltage at this pin is sampled at 130 µs
intervals to determine the trim level. The output can be dynamically
trimmed during normal operation, however it is not recommended
to use this pin in an external analog feedback loop.
Refer to Table 1 for a summary of the TRIM pin functionality and the
recommended voltage/resistance that should be applied to this pin.
Operating State
Remote Sense / Slave Operation
Adaptive Loop Operation
Adaptive Loop Operation
Trim Mode
Trim Active
V_OUT = 20* V_TRIM
Trim Inactive
V_OUT = 48.0 V
Trim Pin Function Summary
V_TRIM
<0.45 V
R_TRIM
<1 kΩ
>0.55 V ^[2]
>3 kΩ ^[2]
1.00 V to 2.75 V
4.32 kΩ to 49.9 kΩ
>3.20 V
>10 MΩ
Detected and Latched
At application of V_IN
when ENABLE first transitions high
At application of V_IN
when ENABLE first transitions high
At every start up when
ENABLE transitions high
Table 1 — TRIM Pin Function Summary
[2] _{It is not recommended to configure TRIM with a voltage less than 1.00 V in Adaptive Loop Operation}
PRM^TM Regulator
Page 30 of 44
Rev 1.2
11/2015
vicorpower.com
800 927.9474