SLVAFX0B October 2024 – March 2026 TLV702 , TLV703 , TLV755P , TPS74401 , TPS7A13 , TPS7A14 , TPS7A20 , TPS7A21 , TPS7A49 , TPS7A52 , TPS7A53 , TPS7A53B , TPS7A54 , TPS7A57 , TPS7A74 , TPS7A83A , TPS7A84A , TPS7A85A , TPS7A91 , TPS7A92 , TPS7A94 , TPS7A96 , TPS7H1111-SP

4 Summary

Table 4-1, Table 4-2, and Table 4-3 include summaries of the architecture cases used in this white paper, to include:

The features of the types of architectures used in these cases.
Examples of the devices used in these cases.
Time periods and equations used in these cases.
The key parameters used in these cases.

Table 4-1 Simple Architecture Cases (No Fast Charge)

Case	Architecture Features	Example Devices	Time Periods	Equations to Use	Key Parameters
Case 1 Basic NR Filter	Precision voltage reference No C_FF	TPS7A20, TPS7A21	Single period: t ≥ 0	V_FB(t): Equation 5 V_OUT(t): Equation 8 τ calculation: Equation 10	τ_NR/SS = R_NR/SS × C_NR/SS R_TOP, R_BOTTOM Measure t_10%-90%
Case 2⁽¹⁾ NR + Feedforward	Precision voltage reference C_FF installed	TPS7A13, TPS7A14, TPS7A49	Single period: t ≥ 0	V_FB(t): Equation 5 V_TOP(t): Equation 7 V_OUT(t): Equation 4	τ_NR/SS = R_NR/SS × C_NR/SS τ_FF = R_TOP × C_FF Both time constants matter

(1) With very small or unpopulated feedforward capacitance (C_FF), these devices operate using the analysis for Case 1.

Table 4-2 Voltage Reference with Fast Charge

Case	Architecture Features	Example Devices	Time Periods	Equations to Use	Key Parameters
Case 3 Parallel Fast Charge	Precision voltage reference NR/SS filter Fast charge: (R_NR/SS // I_FC) Optional C_FF	TPS7A91, TPS7A92	Period 1: t ≤ t_CO Period 2: t > t_CO	Period 1: V_FB(t): Equation 5 V_TOP(t): Equation 7 t_CO: Equation 11 Period 2: V_FB(t): Equation 16 V_TOP(t): Equation 15 V_{CO_FF}: Equation 7 at t=t_CO	V_CO = 0.95 - 0.97 × V_REF I_FC (fast charge current) Calculate V_{CO_FF} as initial condition
Case 4 Switched Fast Charge	Precision voltage reference I_FC disconnects R_NR/SS during fast charge C_FF required	TLV702, TLV703, TPS7A52, TPS7A53, TPS7A83A, TPS7A84A, TPS7A85A	Period 1: t ≤ t_CO Period 2: t > t_CO	Period 1: V_FB(t): Equation 17 V_TOP(t): Equation 18 t_CO: Equation 19 Period 2: V_FB(t): Equation 13 V_TOP(t): Equation 15 V_{CO_FF}: Equation 20	Linear ramp during fast charge V_FB(t) = (I_FC/ C_NR/SS) × t V_CO = 0.97 × V_REF typically

Case

Architecture Features

Example Devices

Time Periods

Equations to Use

Key Parameters

Case 3
Parallel Fast Charge

Precision voltage reference
NR/SS filter
Fast charge: (R_NR/SS // I_FC)
Optional C_FF

TPS7A91, TPS7A92

Period 1: t ≤ t_CO
Period 2: t > t_CO

Period 1:

V_FB(t): Equation 5
V_TOP(t): Equation 7
t_CO: Equation 11

Period 2:

V_FB(t): Equation 16
V_TOP(t): Equation 15
V_{CO_FF}: Equation 7 at t=t_CO

V_CO = 0.95 - 0.97 × V_REF
I_FC (fast charge current)
Calculate V_{CO_FF} as initial condition

Case 4
Switched Fast Charge

Precision voltage reference
I_FC disconnects R_NR/SS during fast charge
C_FF required

TLV702, TLV703, TPS7A52, TPS7A53, TPS7A83A, TPS7A84A, TPS7A85A

Period 1: t ≤ t_CO
Period 2: t > t_CO

Period 1:

V_FB(t): Equation 17
V_TOP(t): Equation 18
t_CO: Equation 19

Period 2:

V_FB(t): Equation 13
V_TOP(t): Equation 15
V_{CO_FF}: Equation 20

Linear ramp during fast charge
V_FB(t) = (I_FC/ C_NR/SS) × t
V_CO = 0.97 × V_REF typically

Table 4-3 Alternative References Architectures

Case	Architecture Features	Example Devices	Time Periods	Equations to Use	Key Parameters
Case 5 Current Reference	? Precision current reference ? R_NR/SS filter ? Fast charge modifies I_REF ? Optional C_FF	TPS7A57, TPS7A94, TPS7A96, TPS7H1111-SP	Period 1: t ≤ t_CO Period 2: t > t_CO	Period 1: V_REF: Equation 21 V_FB(t): Equation 5 (use Equation 21 for V_REF) V_TOP(t): Equation 7 t_CO: Equation 23 Period 2: V_REF: Equation 22 V_FB(t): Equation 13 V_TOP(t): Equation 15	V_REF = I_REF × R_NR/SS I_FC during fast charge I_NR/SS during steady state V_CO programmable through FB_PG
Case 6 Soft-Start Only	Soft-start pin (not NR/SS) No noise reduction Optional C_FF V_OS can be significant	TPS7A74, TPS74401, TPS748A	Period 1: t ≤ t_CO Period 2: t > t_CO Note: V_CO = V_REF	Period 1: V_FB(t): Equation 24 V_TOP(t): Equation 25 t_CO: Equation 19 (set V_CO=V_REF) Period 2: V_FB(t): V_REF (constant) V_TOP(t): Equation 15 V_{CO_FF}: Equation 25 at t = t_CO	C_SS (not C_NR/SS) V_OS offset voltage (see Section 2.1.4.3 Linear ramp with offset No PSRR improvement

Case

Architecture Features

Example Devices

Time Periods

Equations to Use

Key Parameters

Case 5
Current Reference

? Precision current reference

? R_NR/SS filter

? Fast charge modifies I_REF

? Optional C_FF

TPS7A57, TPS7A94, TPS7A96, TPS7H1111-SP

Period 1: t ≤ t_CO
Period 2: t > t_CO

Period 1:

V_REF: Equation 21
V_FB(t): Equation 5 (use Equation 21 for V_REF)
V_TOP(t): Equation 7
t_CO: Equation 23

Period 2:

V_REF: Equation 22
V_FB(t): Equation 13
V_TOP(t): Equation 15

V_REF = I_REF × R_NR/SS
I_FC during fast charge
I_NR/SS during steady state
V_CO programmable through FB_PG

Case 6
Soft-Start Only

Soft-start pin (not NR/SS)
No noise reduction
Optional C_FF
V_OS can be significant

TPS7A74, TPS74401, TPS748A

Period 1: t ≤ t_CO
Period 2: t > t_CO

Note: V_CO = V_REF

Period 1:

V_FB(t): Equation 24
V_TOP(t): Equation 25
t_CO: Equation 19 (set V_CO=V_REF)

Period 2:

V_FB(t): V_REF (constant)
V_TOP(t): Equation 15
V_{CO_FF}: Equation 25 at t = t_CO

C_SS (not C_NR/SS)
V_OS offset voltage (see Section 2.1.4.3
Linear ramp with offset
No PSRR improvement