TPS51219_15 Datasheet, PDF (14/39 Pages) Texas Instruments – High Performance, Single-Synchronous Step-Down Controller with Differential Voltage Feedback

TPS51219
SLUSAG1B – MARCH 2011 – REVISED OCTOBER 2011
APPLICATION INFORMATION
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Swtich Mode Power Supply Control
The TPS51219 is a high performance, single-synchronous step-down controller with differential voltage feedback.
The TPS51219 realizes accurate regulation at the specific load point over wide load range with the combination
of three functions.
• 2-V Reference with 0.8% Tolerance. Internal voltage divider provides precise reference (See Table 1 in the
VREF and REFIN, Output Voltage section). A value of 0.1µF is recommended as the decoupling capacitance
between VREF and GSNS pins.
• Integrator. Feedback capacitance connected from the output (COMP pin) to the input (VSNS pin) of the error
amplifier comprises integrator, which increases gain at DC to low frequency region and improves load
regulation of the output voltage. 10nF is recommended as the capacitance between VSNS and COMP pins.
• Differential remote sensing. Differential feedback provides precise output voltage control at the point of
load. Connect VSNS and GSNS directly to output voltage sense point and ground return point at the load
device, respectively. Short GSNS to GND if remote sense is not used.
The TPS51219 supports two control architectures, D-CAP™ mode and D-CAP2™ mode. Both control modes do
not require complex external compensation networks and are suitable for designs with small external
components counts. The D-CAP™ mode provides fast transient response with appropriate amount of equivalent
series resistance (ESR) on the output capacitors. The D-CAP2™ mode is dedicated for a configuration with very
low ESR output capacitors such as multi-layer ceramic capacitors (MLCC). For the both modes, an adaptive
on-time control scheme is used to achieve pseudo-constant frequency. The TPS51219 adjusts the on-time (t_ON)
to be inversely proportional to the input voltage (V_IN) and proportional to the SMPS output voltage (V_OUT). The
switching frequency remains nearly constant over the variation of input voltage at the steady-state condition.
Control modes and switching frequency are selected by the MODE pin described in Table 2.
VREF and REFIN, Output Voltage
The device provides a 2.0-V, ±0.8% accurate, voltage reference from VREF. This output has a 300-µA current
capability to drive the REFIN input voltage through a voltage divider circuit. A capacitor with a value of 0.1-µF or
larger should be attached close to the VREF terminal.
The SMPS output voltage is defined by REFIN voltage, within the range between 0.5 V and 2.0 V, programmed
by the resister-divider connected between VREF and GSNS. (See Figure 23 and External Components Selection
section.) A few nano-farads of capacitance from REFIN to GSNS is recommended for stable operation. A voltage
divider and a filter capacitor to this pin should be referenced to GSNS. Fixed output voltage can be set as shown
in Table 1.
0,1 mF
TPS51219
1 VREF
R1
2 REFIN
R2
10 nF
3 GSNS
UDG-11042
Figure 23. Voltage Reference Connections
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Table 1. Output Voltage Selection
REFIN VOLTAGE (V)
3.3
GSNS
Resistor Divider
OUTPUT VOLTAGE (V)
1.05
1.00
Adjustable
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