Debt Tokens

Debt tokens are interest-accruing tokens that are minted and burned on borrow and repay, representing the debt owed by the token holder. There are 2 types of debt tokens:

• Stable debt tokens, representing a debt to the protocol with a stable interest rate

• Variable debt tokens, representing a debt to the protocol with a variable interest rate

The source code can be found on Github here.

EIP20 Methods

Although debt tokens are modelled on the ERC20/EIP20 standard, they are non-transferrable. Therefore they do not implement any of the standard ERC20/EIP20 functions relating to transfer() and allowance().

balanceOf() will always return the most up to date accumulated debt of the user.

totalSupply() will always return the most up to date total debt accrued by all protocol users for that specific type (stable vs variable) of debt token.

Shared Methods

UNDERLYING_ASSET_ADDRESS()

function UNDERLYING_ASSET_ADDRESS()

Returns the underlying asset of the debt token.

POOL()

function POOL()

Returns the address of the associated LendingPool for the debt token.

approveDelegation()

function approveDelegation(address delegatee, uint256 amount)

Sets the amount of allowance for delegatee to borrow of a particular debt token.

Used in credit delegation.

Parameter Name	Type	Description
delegatee	address	the user receiving the allowance
amount	uint256	the allowance amounts given to user

borrowAllowance()

function borrowAllowance(address fromUser, address toUser)

Returns the borrow allowance toUser has been given by fromUser.

Used in credit delegation.

Parameter Name	Type	Description
fromUser	address	the user giving allowance
toUser	address	the user receiving the allowance

Returns the current allowance of toUser for a particular debt token.

Stable Debt Methods

getSupplyData()

function getSupplyData()

Returns the supply / deposit data for the debt token.

Return values

Type	Description
uint256	principal supply
uint256	total supply
uint256	average borrow rate
uint40	timestamp for last supply update

getTotalSupplyAndAvgRate()

function getTotalSupplyAndAvgRate()

Returns the total supply and average stable rate of the token.

Return values

Type	Description
uint256	total supply
uint256	average stable rate

principalBalanceOf()

function principalBalanceOf(address user)

Returns the principal debt balance of the user.

getUserLastUpdated()

function getUserLastUpdated(address user)

Returns the timestamp of the last action taken by user as uint40.

getAverageStableRate()

function getAverageStableRate()

Returns the average stable rate across all the stable rate debt in the protocol as uint256.

getUserStableRate()

function getUserStableRate(address user)

Returns the stable rate of user as uint256.

Variable Debt Methods

scaledBalanceOf()

function scaledBalanceOf(address user)

Returns the principal debt balance of user.

scaledTotalSupply()

function scaledTotalSupply()

Returns the scaled total supply of the variable debt token.

This represents $sum( borrows / index )$ .

getScaledUserBalanceAndSupply()

function getScaledUserBalanceAndSupply(address user)

Returns the principal balance of the user and principal total supply.

Return values

Type	Description
uint256	principal balance of user
uint256	principal total supply