SBAA832 August   2026 TPS62A208-Q1 , TPS62A212-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Load Transient Response Fundamentals
      1. 1.1.1 Phase 1: Passive Response (Capacitor Dominated)
      2. 1.1.2 Phase 2: Active Response (Control Loop)
  5. 2Parameters Affecting Load Transient Response
    1. 2.1 Output Stage Parameters
      1. 2.1.1 Output Capacitance
      2. 2.1.2 ESR and ESL of COUT
      3. 2.1.3 Output Inductance
    2. 2.2 Control Loop Parameters
      1. 2.2.1 Crossover Frequency, Phase Margin
      2. 2.2.2 Transient Non-Synchronous Mode
  6. 3Step-by-Step Compensation Selection Procedure
  7. 4Selecting Compensation Setting in TPS62A2xx-Q1
  8. 5Summary
  9. 6References

3 Step-by-Step Compensation Selection Procedure

Note: Compensation values are nominal and can vary by ±10%. The COMP pin resistor must be placed close to the pin to minimize parasitic capacitance and must not be left floating.

Step 1 : Define the Application Requirements

Before beginning the calculation, the following application parameters must be established:
Parameter Symbol Description
Target output voltage undershoot ΔVOUT Maximum allowable voltage dip during a load step
Load step magnitude Istep The peak load current step
Output inductance LOUT Selected inductor value
Output voltage VOUT Determines FBRatio and VOUT Range
Switching frequency FSW Set via CONF pin (1.5, 2.25, 2.5, or 4MHz)

Step 2 : Determine FBRatio

The FBRatio accounts for the difference in internal feedback scaling across the four output voltage ranges. It is fixed by the VOUT range, which is configured through the CONF pin.
Table 3-1 FBRatio Values
VOUT Range VOUT(V) FBRatio
Range 1 0.4 – 0.5875 1
Range 2 0.5 and 0.6 – 0.775 1
Range 3 0.8 – 1.55 2
Range 4 1.6 – 3.3 4

Step 3 : Calculate the Target Compensation Value

Use Equation 1to calculate the recommended (gM × Rc):
  • Equation 1. g M × R c   ( V V ) = 78571.43 × I s t e p ∆ V o u t   × FB Ratio   × L o u t

Where:

  • Δ VOUT= Target VOUT undershoot (V)
  • Istep = Load step (A)
  • LOUT = Output inductance (H)
  • FBRatio = From Table 1 above

Step 4 : Select the Compensation Setting

From the given table, select the COMP setting whose gM × Rc value most closely matches the calculated result:
Table 3-2 Compensation Setting
Compensation Setting gM × Rc
COMP 15 8.5
COMP 14 6.8
COMP 13 5.75
COMP 12 4.6
COMP 11 3.75
COMP 10 3.0
COMP 9 2.5
COMP 8 2.0
COMP 7 1.75
COMP 6 1.4
COMP 5 1.125
COMP 4 0.9
COMP 3 0.75
COMP 2 0.6
COMP 1 0.5
COMP 0 0.4
If the calculated value falls between two settings, choosing the higher setting provides more loop gain and tighter transient regulation. Selecting the lower setting reduces the risk of instability when output capacitance is at its minimum due to derating.

Step 5 : Set the COMP Pin Resistor

Configure the COMP pin using the corresponding resistor from given table, placed between the COMP pin and GND using E96 series values:
Table 3-3 Configuration Options for TPS62A2xx-Q1 through the COMP Pin
COMP Pin Configuration Compensation Setting
Connected to V_IN `COMP 15
100kΩ to GND COMP 14
33.2kΩ to GND COMP 13
16.9kΩ to GND COMP 12
10kΩ to GND COMP 11
6.3kΩ to GND COMP 10
4.2kΩ to GND COMP 9
2.8kΩ to GND COMP 8
1.9kΩ to GND COMP 7
1.3 kΩ to GND COMP 6
887Ω to GND COMP 5
576Ω to GND COMP 4
365Ω to GND COMP 3
210Ω to GND COMP 2
100Ω to GND COMP 1
Connected to GND COMP 0
Important: The COMP resistor is read during device startup. Changing the resistor value during operation has no effect. In fixed-OTP devices, connect the COMP pin to AGND.

Step 6 : Verify Loop Bandwidth and Minimum Output Capacitance

The transient response of the converter depends on which operating region the control loop is in:
  • In regulation: response is determined by the loop bandwidth
  • Loop saturated: response is limited by the maximum inductor current slew rate
TI recommends calculating the minimum output capacitance for both criteria and selecting the larger value.

6a : Loop Bandwidth Constraint

The loop bandwidth must satisfy the following under all operating conditions, including all applicable derating factors:

Equation 2. 100 k H z ≤ B W ≤ M i n i m u m ( 600 k H z , f s w 5 )

6b : Minimum Capacitance: In-Regulation Criterion

If the converter remains in regulation, the minimum output capacitance required is:
Equation 3. C o u t ( m i n ) ( r e g ) = 1.59   ×   10 - 6 ×   g M × R c L o u t × B W × F B _ R a t i o

6c : Minimum Capacitance: Loop Saturation with TAM Disabled

TPS62A2xx-Q1 family employs a Frequency-Regulated Constant On-Time (F-COT) control architecture, which maintains a nearly constant switching frequency while preserving the fast transient response characteristic of COT control. The control loop is configured through a single external resistor on the COMP pin, selecting one of 16 discrete internal compensation settings (COMP 0 through COMP 15). Each setting corresponds to a specific value of the internal compensation product gM × Rc, ranging from 0.4 to 8.5, which determines the crossover frequency and governs how fast the converter responds to load transients.

The design task reduces to calculating the required gM × Rc from the application's transient requirements, selecting the closest available setting, and verifying the minimum output capacitance requirement is met.

When the load step is large enough to saturate the control loop and the TAM feature is disabled, the minimum output capacitance is:

Equation 4. C o u t ( m i n ) ( s a t ) = 1 ∆ V o u t ×   ( ( I p k 2 × L o u t 2 ×   ∆ V L ) + ( I S t e p [ T o n - T t 2 ] ) )

Where:

Equation 5. I p k =   I D C +   I L ( P P ) 2
Equation 6. I L ( P P ) =   I n d u c t o r   c u r r e n t   r i p p l e  
Equation 7. ∆ V L = V o l t a g e   a c r o s s   t h e   I n d u c t o r = M i n i m u m   (   V i n - V o u t ,     V o u t )
Equation 8. T t = T r a n s i t i o n   t i m e   o f   t h e   L o a d   S t e p
Equation 9. T o n = V o u t η × V i n   ×   1 f s w

6d : Minimum Capacitance: Loop Saturation with TAM Enabled

When the load step saturates the control loop and the TAM feature is enabled, the minimum output capacitance is:

Equation 10. C o u t ( m i n ) ( s a t _ T A M ) = 1 ∆ V o u t × ( ( I p k × ( T s w - T o n ) ) - ( ( T s w - T o n ) 2 2 × V o u t L o u t ) + ( I v a l 2 × L o u t 2 × ( V o u t + 0.6 ) ) + ( I S t e p [ T o n - T t 2 ] ) )

Where:

Equation 11. T s w = 1 f s w
Equation 12. I v a l =   I D C -   I L ( P P ) 2

Note: TAM is available only for VOUT Ranges 1, 2, and 3. It is not available for VOUT Range 4.

6e : Final COUT Selection

Select the minimum output capacitance based on the applicable saturation criterion for your design:

VOUT Range TAM Status COUT(min) Selection
Range 1, 2, or 3 TAM Enabled max(Eq. 4, Eq. 10)
Range 1, 2, or 3 TAM Disabled max(Eq. 3, Eq. 4)
Range 4 TAM Not Available max(Eq. 3, Eq. 4)

Always apply appropriate derating to the selected capacitor to account for DC bias voltage coefficient and temperature effects.